11:33 -- The circular ring is connected to a constant voltage (V+), so it's at AC ground. It prevents signals in other parts of the circuit from affecting the voltage of the disc inside the ring. (It's a "guard ring".) The transistor's collector (C) is connected to this ring / AC ground. The disc inside the ring is connected to the transistor's base (B). The S-shaped piece of PCB that's connected to the transistor's emitter (E) is a section of transmission line, which resonates at a particular frequency and which determines the circuit's frequency of oscillation. Since one end of the S-shaped piece of PCB is connected to the transistor's emitter (E), which is the signal source, and since the other end of the S-shaped piece of PCB is connected to capacitors which are connected to ground (so that the far end of the S-shaped strip is at AC ground), then the S-shaped strip is a 1/4 wavelength resonant section of transmission line. There is feedback between transistor's base (B) and its emitter (E) through the space between the short strip of PCB ("stub") that's connected to B and the section of the S-shaped piece of PCB that's connected to E. The size of the space between that stub and the S-shaped piece of PCB that's connected to E largely determines the degree of coupling (feedback) between the transistor's base and emitter. The longer the space or the narrower the space, the greater the coupling / feedback. So the circuit is a one transistor oscillator (specifically, a grounded-collector oscillator), having a resonant circuit that's connected to the transistor's emitter, and having some coupling / feedback between its emitter and base.
@@therealjamespickering -- The circuit generates microwaves. The microwaves are radiated by the little antenna. When something moves through the field of microwaves, some of the microwaves are the reflected to the antenna, where the reflected signal is absorbed, amplified, and combined with some of the microwaves being generated by the circuit. The result is a small change in the circuit's normal voltages, which the rest of the circuit (the rectangular chip) then detects.
@@kevinbyrne4538 Ok, that's much clearer, thank you! So the S-shaped track oscillates at a frequency of 3.18 GHz and the interaction between this and the disk attached to the base results in a certain voltage to be passed through the emitter? Movement in the room would then result in variations in the voltage? Does the board only output a high/low digital signal, or is it an analogue signal that could be used to determine something about the size/velocity of the object?
@@N1gel Haha, I don't even know the basics of electronics, but I get drawn into these. I at least have an idea of which components do what, it's just the whys that Confused me, lol. My list of questions never ends and at some point I will know more, but right now, I still love Clive's vids despite my lack of knowledge...the big surprise I was getting at you know, lol.
@@watsoft70 Glad to know I'm not the only electronics-noob in the audience. Whenever he talks about complicated circuits like this, I'm lucky if I can even follow along half of what's going on.
@@N1gel ... some things are just beyond the ken of mere mortals, and are not meant to be known the wot of. Microwave RF is clearly for wizards and other ethereal beings.
If Clive says it's complex it's really complex. Another really interesting video Clive thanks for all the hard work you put into these. Glad I stumbled on your channel many moons ago, it fascinates me how all these things work and makes me want to get into making a few projects myself
Loved this video! The fact that you tried to comprehend the magic of RF and still put out this video - the transparent film screen showing the back was a great way for you to explain of your thought train in a very slick way!. Always look forward to your new content, I’m pretty sure I’ve watched all your back catalogue :-D
Hehe, I also made those “simple” (slightly illegal) FM transmitters when I was young, most often with a preceding microphone amplifier, to become a small bugging device. Often choosing close to 88MHz or 108MHz, and then any ordinary FM-radio (preferably small and hand held) could be used as receivers. I learned then, that there was a big complexity to RF-electronics, since I put a lot of effort in doing very nice and clean builds, with often no good results, while a class mate made a very “ugly” build (blobby soldering, wires not cut close to the PCB etc) and that worked better than any of the rest of the class mates. It’s fantastic that a simple circuit like that actually ends up as a FM-transmitter. The simplicity to build things like this for FM an AM, together with the avast amount of existing equipment, is actually why I feel a bit “scared” that DAB will “destroy” the possibilities for future young kids, interested in electronics, to test and learn in an exiting (slightly illegal) way. Of course you can do a lot of MUCH cooler things today, with all sorts of micro controllers and advanced chips, sensors etc, but not at the same low level. I’m glad Sweden postponed the switch to DAB. It really feels meaningless, since you could get the digital feeds via mobile data streams and the cost to switch all existing analog equipment would be enormous. It have played out it’s role... Keep at least some of the current FM-band analog (as well as the AM-band) as a backup system and for the kids to play with ;) Btw, we soldered the antenna (normally measured to a quarter to the wavelength) to one of the loops of the wounded inductor.
The Concentric Circles thing is the actual Antenna Element Back Plane . The Squiggle Line Track simply a Load Inductor doubling as the Antenna. If you measure the Distance between the Squiggle Track folding back on it's self you will find it a fraction of the actual operating frequency in .wavelength.. Probably 1/8th or 1/4 wavelength.
The rectangular track on the base pin will probably be 1/4 wave resonant stub too. Don't forget to account for velocity factor when working out the frequency, which is approx 0.5 on FR4.
Argh. I should read more before posting. If you think of it as a delay line one end is the frequency of the oscillator right now and the other end is the frequency of the oscillator a few pico seconds ago.
I bet it's the same ghost that switched my grandmas stove on and ran my water heater for 4 days straight. If you manage to catch it, make sure it can't hurt anyone again.
This reminds me of a gadget I built before touch sensors existed. I used a PIC to generate PWM into a coil, which coupled with another coil. Somehow I could measure the phase between coils, which I put through an op-amp and back into the PIC. The theory was that my finger would change the phase. They laughed at me, said it can't work, but it did! I put two of these in a box and by sliding my finger up and down on the surface, I controlled a PWM fluorescent dimmer. Happy memories. My goal was to make a water-proof switch.
That's how inventions are made. Though a waterproof switch is much simpler to make, just get a reed switch and a magnet. That's how Nikko did their submarines.
Before touch sensors were around? Seriously? How about 1978 when I made touch sensors using CMOS 4011's? PIC's didn't even exist then. The circuit was simple, touch one spot to turn on and the other spot to turn off. Have to say though, the capacitance coupled sensor would definitely be better and could be made waterproof.
not sure if it was intended as part of the joke, but arthur c clarke was a radar specialist in WWII so I don't think microwave tech was very magical to him.
Hi Bigclive - really interesting video - I remember UHF/Microwave construction being described to me in the late 1970s as a bit like "plumbing" - the usual headache when designing higher and higher frequency circuits was trying to overcome and eliminate stray capacitance, but as you get towards the top end, they stop being a "problem" and start becoming an "enabler" - but you instinctively realise that :) What's more interesting to see is that (compared to the tolerances within microchip fabrication) the relatively crude technology behind copper etching can be used to great effect. It's a bit like looking at plans for a fairly crude valve amplifier and realising that the "cleverness" is all down to the physical construction, which we've all kind of forgotten with the ability to cram more and more components into an ever decreasing space to overcome design flaws This is a perfect example of less being very much more :)
Clive, as a 50+ y/o electronics and radio enthusiast, may I say, if your video's were available when I was doing my training, I would be "up there" now, I really enjoy all your "tear-downs" and the way you detail your explanations. They come across so well. Even something like this complex uWave circuit. Well done.... You're a top bloke!
Sometimes I wonder what effect it would have had on my own learning if RUclips had been around when I was young. It'll be interesting to see how it affects the current generation. They have a lot of technical materials and tools at their disposal.
@@bigclivedotcom Yea, I'm so envious! One of my first "serious" books was a Ladybird book Making a Transistor Radio when I was about 10 - Remember the OC71?
This break-down caused me to realize that not every part of a circuit is either positive or negative relative to a connected part; but rather, the relationship can be more complicated; time-based or based on detection/externalities.
I was a broadcast engineer for a couple of decades, but RF was never my strong suit. I could keep big transmitters running, but I was way more comfortable with studio gear and computer stuff. I totally understand what you're saying!
This is a awesome talk on rf doppler detectors, the bit in the beginning which covers the oscillator and how one can modulate the amplitude is gold. Love it, thanks Clive!
Make sure and redesign your room to be the right size resonant cavity faraday cage. Make sure it is grounded. There, now your idea would work, but the sound of people screaming from sudden blindness would be your early warning alarm...
Back in electronics school, my teacher had been a elec tech for radios in fighter jets. He told the story of a jet that would have radio troubles. After some time of trying to figure it out,, the E7 boss man, handed him a can of polish, and told him to polish the inside of the box the radio sat in... It seems that the box was a capacitor in the circuit. ... hmmm Well, the polishing worked,,, at least that is what we were told... Thanks and keep up the good work.
I love these relatively long videos, it's a lazy Saturday afternoon, wife is having a nap with the little one and I can just veg and watch you explain cool stuff. Some of your previous videos have given me great ideas for work projects too (Rpi/arduino stuff), so cheers for that too!
Amazing explanation and homework.. Especially because of the super zoomed PCB picture that was used. I'm sure it helped the viewers understand the PCB a lot more easily. Keep up the good work.
I was on the development team of the C&K/Honeywell DT-7xx k-band Dual Tec microwave/pir motion detectors back in Y2K. I did a lot of GTEM work for rfi and international certifications and UL listing. That round pad pad on the with the positive ring could be adding a few pf capacitance to keep rf noise out of the transistor. RF can be funky at gigahertz frequencies. I watch your videos to jog my memory. My kung fu is old and haven't touched an oscope or frequency analyzer since 2004 working on Pave Paws. That was SLBM rocket science ;)
A hybrid coupler in ring configuration ("rat race coupler") perhaps. These couplers typically have four ports. Power input at port 1 splits and travels both ways round the ring. At ports 2 and 3 the signal arrives in phase and at port 4 it's out of phase and cancels. The reflected, out of phase signal (from your body) can be made to "unbalance" the ring which effectively brings one port to a higher potential than the other ports. Those eclipsed portions of ring might be the port couplings. Just a guess- I am not a µwave engineer (but have played with transmission lines in the past).
I like it and me too. C band satellite LNB pre amps when 120$ was entry price for a single NEC transistor with a much improved noise figure. Had no real business ordering those and resurrecting dead ones from lightning surges, but I was still more successful than not. Only thing I can recognize here is the quarter wave tank described as the only rectangular item on the board, hanging off the collector. 14:06 Those were very commonly used in that field for side by side coupling of the mixer signals. CRS about too much of it these days, but we are talking mid 80s too. End of the day, way too pricey for me to play and win.
I think this is a voltage controlled oscillator, it doesn’t use a fixed frequency. As others have said, the circular elements on the back plane are part of the antenna. For this sort of circuit to work the antenna needs to have an outrageously high Q, and ideally a pretty low radiation resistance, which a loop antenna provides. Essentially the ring looks to be a loop antenna acting mostly as a receive antenna. It’s coupled to to the transmit antenna with a sort of hybrid between a gamma match and a Patterson loop style capacitive network. The 1k resistor and the two adjacent capacitors right before the sense input are an RC pi filter tuned to the oscillator’s stable frequency. When the environment around the sensor changes, the amount of reflected power and the phase of the received signal changes slightly, which causes a change in the circulating current in the receive loop, which causes the complex impedance on the oscillator output to change, which changes the oscillator’s frequency. The frequency change means the signal will move relative to the pass band on the RC pi network, changing the attenuation of the signal and altering the voltage at the sense pin, and the chip just triggers on the change. If you have an RTL-SDR dongle or similar you should be able to confirm this by watching the signal in the waterfall. I bet it swings like mad when you sweep your hand near the sensor. Clive, if you don’t have an SDR handy, I’ll order a couple and put it on the spectrum analyzer, and I’ll also send you a little SDR dongle. Super handy little gadgets for poking at RF circuits like this.
Indeed there's a github repo with information about this module (jdesbonnet/RCWL-0516) which mentions: "finally found the signal at 3.181GHz with the HackRF One SDR! One interesting observation: waving my hand in front of the sensor causes significant changes in the transmitting frequency, shifting by up to 1MHz"
Matthijs van Duin that’s interesting, I would actually expect the swing to be much bigger for it to be based on the changing attenuation of the band pass filter. 1MHz swing on a 3GHz signal would probably only be a fraction of a dB even at the steepest part of the filters curve. I wonder if it’s using the op amp that’s on the input of the chip as a phase comparator or something similar.
Many years ago as i mooched around the local library I noiticed that a book enttled 'The Deadly Fuze' never moved. Eventually curiosity got the better of me and I took it out.Turned out to be the story of the development of the WW2 Proximity Fuze. Built into shells and fired up the barrel of a gun! And this was in the days of valves!! Can't remember the operating frequency but acorn valves could get up to about 500Meg. Used in anti aircraft shells and ordinary artillery shells. And now we've got shells with GPS built in!!!
I bought some of these for a prank on my boss (we are in an office prank war... he started it... lol) and I wanted to know how it worked. Eventually I decided I’ll never know and that all I needed to know is that it did work. Fast forward 2 months and here I am watching Clive on an 8 month old video on the chips I bought. I have been a fan for two years, and somehow this is the one video I missed. Haha, thank you for this closure!
I bought two of these intending to use them as some sort of alarm, (instead of the LED you have) but did not do anything with them. Now I understand what's going on and can proceed further. Thanks a lot for doing this video and also thanks for the many knowledgeable comments from everyone.
The feedback from the collector to the base is in the transistor, mainly the internal capacitance between the collector and emitter. The square trace connected to the base is less an inductor/capacitor and more a delay line. The oscillator operates as a common base amplifier. The "squiggly" emitter line is a delay line. The disk of copper on the bottom behind the transistor is simply a ground plane. Some capacitance is there but it's unintentional. The ring of copper is the actual antenna. The ring and the disk ground plane act like a fresnel lens and makes the radar output more like a dipole antenna. When you move towards or away from the antenna, not only do you cause a doppler shift but you mainly case the frequency to shift (you're now part of the tuned circuit. At cm waves both are pretty much the same thing). The wiggly part of the emitter track introduces a delay from the frequency a few pico seconds ago and mixes it with the frequency that's happening now. In phase oscillations use less current than out of phase oscillations. The increased current drain for an out of phase signal is dropped and filtered by the emitter resistor (which is where the real feedback and transmit occurs) and the associated emitter/ground capacitors for detection.
@@pahom2 Everything is an antenna. In your case the dual squiggly lines is probably being used as an antenna and phase comparator. Remember that at these frequencies there is no real tuning inductor or tuning capacitor. Everything (including you) is part of a tuned circuit.
I was trying to figure out how the circiuts work (and they do very well!). Your video was the best and honest video I found! I highly (!) appreciate all the effort and time you have put into making this video, althought english is not my first language and I do not undestand every piece!
I think you are correct with the screening you spoke of. Back in my army days that screen was made of copper components and used to tune the device to see it's target.
Did anyone else notice how Clive drew his own face in this video? - Just look back at the part where he draws the diagram of the P.I.R. sensor at the top of the sheet.... Now, tell me that's not a self portrait! Thanks, Clive, for another truly enthralling video on something I know absolutely nothing about. - Give me valves (tubes) and high voltages any day. But, we shall learn........
That RF oscillator could be used as the volume oscillator in a theremin. It would be interesting to attach an oscilloscope to the 'sense' point and see how sensitive it is. I might buy some of these and try to build a theremin.
The ring is a resonator at wavelength equal to its circumference. The top of the ring is pinned firmly to VCC by those bypass capacitors forcing that to be an E field node and the bottom to be an anti-node. The collector and emitter have opposite phase so that the meander line couples to the resonator on the back. Do those two vias on the disk connect to the base? They seem to be about -120/240 degrees away from the top standing wave node. Combined with the transistor characteristics and the base capacitor overlap, I predict this brings the positive feedback into phase with the resonator. Any Doppler effect shift will be f0 (v/c). That disk might couple to reflected energy so that the same transistor mixes those two signals with the 1k -- 1 nF forming the LPF to reject the carrier and sum frequencies.
I have some ceiling lamps I bought from Costco that I'm sure have this technology in them. I love when the light goes on when I enter a hallway. For the first 2 months, we all said thank you to the light every time.
My parents bought some cheap PIR ceiling lights recently. I installed on in the laundry. Its quite nice, except for the fact it has no sensitivity adjustment.... And I know I could change the sensitivity by swapping components. But the manufacturer has welded the damn thing shut. The only way to open it is by cutting it.
@@tin2001 The one I got has a remote and I think there's a sensitivity adjustment. Also the color temp, time it stays on, etc... Now if I could only find the remote...
I have a bunch of these and they are great, but I never bothered to try to figure them out, I didn't do very well in my RF and wireless classes when getting my degree. I understood diversity and multipathing, QAM and PSK, but for actually how circuitry worked and a lot of the math involved, not a chance. That stuff is black magic, to the people that really know it, much respect.
I at one time worked on 45w 850mHz transmitters at the factory. I would tune the circuits be adding or removing silver solder from the copper patterns on the board. They were very sensitive to anything being moved around the power transistors.
@@stargazer7644 Not really. A 850mHz antenna is only about 6 inches long. These were for a early car phone system base station, before cellular phones.
@@oldmgbs2 - Star Gazer is busting your chops a little, for using the 'milli' prefix when you (presumably) intended the 'mega' prefix -- because a sub-1Hz frequency would (of course) need a hella large antenna :-)
Clive’s got it right he could be an Electrical Engineer... As my intro to EE professor said the difference between science and engineering is that engineers estimate, like Clive and his capacitor values being feasible, and scientists require exact values meaning they’re not as flexible dealing with real life components’ tolerances.
5:20 "The ZTX300 was also one." Instant flash back to Analogue Electronics in Higher Physics, 1986-7, where we had a tray of components and the transistors were ZTX300 and ZTX500.
Thanks for this. I bought a dash cam hardwire kit which is apparently a movement detector and it's so light I thought it was fake. All it had was one of these circuit boards. I now see that a tiny circuit is all it takes to make a microwave transmitter!
Im only a low level entry into RF circuits but I am aware in microwave frequencies an antenna called a discone is used most common. They tend to use a capacitive 'hat' and obviously get smaller the higher the frequency, so I think you have a very squashed discone antenna with all the relevant coupling components. The idea with RF is you want as much power thrown out as possible without any RF reflecting back down the feed to the transmitter or damage will occur. I know its very critical with high power outputs, but not so sure with very low power like this but it could have an effect if not controlled properly. It is called a discone because that is exactly what it looks like, a disc on a cone with an insulated separator between them. The disc is fed with RF and the cone is the ground reference and the size and angle relationship ( radius of disc and angle/length of cone with solid cone and disc or using rods as a cone and disc ) between them determines the frequency you want to transmit at. As mentioned by another commenter further down the receive parameters of the antenna will usually be compromised by a fraction of the desired transmit frequency ie 1/2 wave, 1/4, 1/8, 3/8 etc are typical because of size limitations on the board or your available space at home because the actual size required for a 1:1 transmitter in most cases would be far greater than the space available. Reception through an antenna does not need to bother so much with sizes of things as all it does is alter the amount of energy/noise/interference available to be received. In short, the antenna length/size must be a fraction of the wavelength of the frequency you wish to transmit at and the load on the transmitter device should be as close to 50 ohms as possible to prevent a dead short, because transmitting RF is almost a dead short and a lot of energy is at the transmitter in commercial antennas which is why you should never EVER touch a live transmitting element as you WILL get burned lol. With an AM/MW antenna the entire pole is live, ShortWave uses very long wires across towers and FM uses lots of types from yagis, log periodic, ground plane X shapes, monopoles, discones, dipole etc.. Basically the higher the frequency, the shorter/smaller the antenna length. Interestingly, behind those small to massive "snare drum shaped" microwave transmitters you see everywhere is just either a small discone, bowtie or dipole element in the center. The drum is just a reflector for line of site comms. :) Probably got some bits wrong but didnt want this to go on forever.. which it has lol
I'm using one of those microwave sensors as an under-monitor movement sensor. It is used to switch on an LED strip under my monitor when movement is sensed. The problem I have with these is that the sensing is patchy. They can often see me over the room (and through a wall) but will often not detect when I'm sitting at the keyboard (2ft away) moving my hands about the keyboard and to mouse etc (1ft away). My current solution is to have one under the monitor looking at me and another blu-tac-ed under the wooden desk and mousepad. I've never yet worked out the front/back of the sensor to find the most sensitive side. I've been tempted to try a PIR sensor on the monitor instead but never got around to trying yet.
i just did a thing of which i am inordinately proud. i bought a bunch of these, and decided 3 secs was too brief for the output signal. so i found the data sheet, learned to solder 0603 smd bits, removed the 10nf timing cap, popped a 100nf one in it's stead, and voila! it now switches for 30 seconds...and for my next trick, i just ordered some arduino nano PCBs and all the bits on the BOM. i am only going to try and make my own 'arts and crafts' arduino nano! and a mere year ago i was horrified by the thought of even soldering the headers on one. i learned it all from watching YT vids.
I once worked in a firm that was involved in microwave sorts of things. You can make a tuned circuit by drilling a hole in a bit of metal and putting a plate on either side. That's your inductor and capacitor right there.... Also wave guides are a lot like plumbing just very precise.
Well you did a fine job splaining it, I was lost but then caught up. Flooded kansas again. Rain for the last 5 days. Supposed to be sunny tomorrow. Cheers.
@@tin2001 done, if you can send me a 545rfe transmission for the truck I bought. I'm driving myself crazy not being able to go out and finish pulling it, make sure its what's wrong.
Fascinating..Ive just bought an outside floodlight with microwave sensor from CPC, havnt put it up yet and wondered how it worked compared to PIR ..Thanks Clive :)
Great to watch you second guess what and how the designer was trying to achieve. There must be a bit of detective Columbo in your DNA. One more thing....
I think of things like this as engineers taking physics and breaking its back over their knee. In ten years it will probably be taught to 14 year-olds and be considered just normal everyday stuff. I love watching the way technology, behind the scenes, is advancing with quiet, almost, unnoticed, steps. Thank Clive for the excellent video.
Microwave RF design is something magic. As I'm not a wizard I don't understand much of it. As a ham radio operator I want to work on the GHz bands as well some time in the future.
EXCELLENT Video BigClive, once again you bring us mere mortals outstanding, interesting and simply awe-striking photo overlays with sublime PCB Exploded views, thank you immensely
*claps hands* Yay! A new BigClive video! - And I just got my first meter, and a PCB holder 😁 Double yay! ... now to figure out how a meter works, while I wait for a kit that'll teach me the basics 😂 *looks at wall outlet*
Congrats on getting on the road to start learning electronic. Do not do what I did with my first meter and a wall outlet: I tried to check if neutral was really connected to ground by measuring the resistance between both, I was lucky as it only damaged the resistance range I was using. It was a passive analog meter, I'm not sure a modern electronic meter would fare that well.
@@SlyPearTreeThanks! And that sounds like an exciting moment! Haha Kinda sounds like a thing Clive should test out, while demonstrating to us (not you included ;) newbies how a meter _should be used_ and *not* used 😂 I'm still tip toeing around and reckon it'll be a good while before I start dabbing with the mains (So for others; yeah if it wasn't obvios, I was kidding xD). Rather safe than sorry in this scenario 😁
Slypeartree a proper modern meter should not be damaged by that. That’s actually one of the tests Dave Jones on EEVBlog does when testing meters - full mains voltage on resistance range. Some fail spectacularly. Older analog meters will release the magic smoke and possibly detonate the battery.
@@stargazer7644 *giggles* Since I still have my childhood SNES I hate to imagine where I'm at when I hit 60 😂 - Thanks for the feedback! FYI: I did test out my meter on a diode and after some fiddling around (It's an 'automated' meter; probably should've picked a conventional one instead) it, to my amazement, worked. Let China be praised by the sun,... for their cheap electronics! 😁
Thank you Clive, a very intriguing, detailed explanation. It is fair to say that I need to watch this many more times before any information permeates into my brain (and is retained). Thank you again; you help me enjoy learning (slowly).
Clive, thank you for teaching me about this device, I've had one in the drawer for quite awhile now. I think i will temper with it's C-TM with resistor and maybe short it out. What i really wanted from this device was the magnitude or perhaps frequency of detection and not so much staying on for a duration.
yet another great vid, always wondered but assumed it was short range radar. the eclipses you talked about, in my experience ... the capacitance is used to tune an antenna wire or in this case the track. for example the 2.4ghrz band ( most wifi traffic and bluetooth ) and the antenna shape and reflectors on the back help with beam forming ( rf shaping or direction ) so... 300 (reference to speed of light acepted figure for antenna calculations) devided by 2400mhz known as 2.4ghz will give you 0.125 of a meter or 12.5cm ( the required antenna electrical length for 2.4ghz) which can be shortened by introducing a week capacitance to allow the physical length of the antenna to be reduced to make it more manageable. most modern antennas are designed this way to reduce physical length without disturbing antenna performance or in some cases actually enhance it. hope im right and this helps.
You're not wrong. Track width and capacitance values of mere picofarads or the reluctance or inductance of micro-henrys, can make a large difference in resonant frequency... Very careful design of layout track width, path and component values are critical... That's why RF equipment has so many variable Caps and tunable coils....or you'd never get an accurate or stable frequency... Tuning RF equipment is an art in itself..... Peace, Keith......
Pretty clever. You really gotta stare at it to see all the layers. The single transistor is being used for several things at once. The base is capacitively balanced between the TX and RX in such a way that if they don't cancel each others opposing capacitance charge the difference will change the bias of the transistor. A lot like how a phase lock loop can demodulate FM. It's seems a lot like just a microwave frequency version of a phase lock loop metal detector that's been cleverly manipulated out of a single transistor and some passives. The metal detector doesn't beep unless you swing it, but in this case the coils are stationary and the metal moves. The higher the frequency the more the water in the soil reflects back on a metal detector. That's why they only use around 7khz.
Clive it’s a good job I love the sound of your voice because despite really trying I didn’t understand a f*cking thing tonight. Thanks for posting anyway though I really appreciate the hard work you put in to educate the masses.
I assume the disc and ring are a circular or spherical polarised antenna. The FPV community might say it looks like a linear 5.8Ghz patch antenna with a ring around it. There are many designs of FPV microwave aerials, some appear to short the signal to ground (usually with a twist or three) while others are capacitive - an interesting one which is circular polarised and can be printed cheaply on discs of PCB. It was provided open source by RF legend Maarten Baert. It's currently the most popular design www.maartenbaert.be/quadcopters/antennas/pagoda-antenna/ It would be interesting to grab a load of these detector boards and try overclocking the range using higher voltages, enclosures, Pringles tins etc... Great video as usual Mr Clive!
I used to make those FM-band transmitters too-- circa 1967. In those days we could buy "Poly-Paks" transistors, basically floor-sweepings. But they were perfectly usable 2N706's, 3 for $1. You could put a crystal microphone onto the base and pick up the signal and sounds for a dozen feet or more. Fun times. It was legal in the USA at power levels up to 50 milliwatts and 3 feet of antenna. You have some base-emitter feedback there.
On the note of the "intelligent" powerbanks that shut off... How about a video about modifying them to either not do that or turn down the current they require to be drawn to stay on, if possible? I've had tons of projects where I thought "I could just use a powerbank to power this" and then these "intelligent" ones ruined that idea, especially ones that require something like 200mA minimum to stay on. There's simply no way to use low power stuff like a simple 1 LED light (ikea jansjö USB for example) with long runtime in mind from it because the powerbank will just turn off after 10secs :(
If you ever get interested, I'd love to hear your explanation of mass spectrometers and the quadropole mass selector. They're all about how alternating electric fields interact with ions of different masses.
The mode which always resets before triggering again is useful when you're doing the on/off timing externally. This way the external circuit can continously detect movement.
If you hook up these to a ardunio and solder a wire to the analong input of the chip (I'd have to look which one it is as I don't remember) You can also get reflection intensity on a graph via the serial monitor with a little programming. Put a couple of these on a parabolic dish and you have a low power radar!
this was jolly interesting. for several reasons. today i bought, for a quid, a crappy thing consisting of a fake cork, with 3 button cells in it, and depending from it are 2 lengths of wire, between which are soldered smd leds. it is intended to be put in an empty bottle. i bought it to play with a microwave motion detector. the amusing bit is when i walked in asda, with the device in my pocket the security alarms went mental! and then in Sainsbury's and Lidl too! i can only assume the lengths of wire, which were tightly wound in coils in the packet had an inductance which was able to take a charge from the security gubbins EM field. fascinating. i actually came here to discover which is the front and which the back of my micro-wave pseudo IR jobbies. i couldn't work it out as they seem to detect motion anywhere.
Some motion detectors used in security/burglar systems use both a PIR and a microwave detector (called "dual-tech" in North America at least). Both sensors have to detect/trip in order for the zone to be considered violated, which greatly reduces false alarms.
The oscillator circuit is probably common collector. The feedback is from the emitter to the base through a transformer to get the required amplitude increase. Since the collector is grounded, the collector to base capacitance becomes part of the tank circuit and the Miller effect is eliminated. The transistor can then operate at the highest possible frequency.
BISS0001 chip is special for PIR controller (Passive Infra-Red), but you can modify this chip into another sensor controller like in this video the chip as a micro-wave proximity sensor.
I think the capacitor/trace array is forming something similar to the old ladder line, which is in effect a series of tank circuits. It allows an antenna to be resonant at an improper dimensional characteristic. In effect it's a microwave transmatch to make use of the PCB as combination resonant body and RF emitter. It's been a few years since I was too deep in this stuff, but that's my take (subject to correction) on the oscillator/transmission line/antenna you have there. The presence of the human in the vicinity of the RF field detunes the whole affair, triggering the off delay. It's a lot like a Dip meter. Back in the late 70's this was used for some alarms. Heathkit had one I built for a friend's TV shop, and it had a discrete telephone dialer in it as well, which you set using dip switches. Once triggered, the dialer would use a reed relay to dial your home number (programmed by the switch array), then you would have an open mike in the room so you could listen to the people stealing your stuff.
Clive - I finally figured out what you meant. I can use the 3.3VDC Hi circuit to close the ground loop for the camera's dry input. It took me a month. I feel slightly dumb. :)
I've used them as movement sensors in a few motion activated arduino systems. One thing of note (apologies if others have already said this) is they seem to work on detecting motion of fluids (bearing in mind the human body is mostly water). You can prove this by first waving an empty water bottle in front of it, then waving a full water bottle.
Wonderful 🎆🎇🎆🎇 As an EE schooled in the 70's - designing these types of RF circuits was referred to as 'black arts' - it is very specialized to the point of being black magic. Now with computer modeling, it is likely far more 'controlled' design, but still so amazing. Wonderful breakdown on it and loved all your visual aids - appreciate the time and effort required for all this. I have been toying with the idea of these for a security grid on our remote property. === All should be getting ready -- as in the forming of this arising 1 world totalitarian state - they will crash food supplies, energy, economies as part of the 'great reset'. So the prudent will Stock food, water and energy, barter items, and overall become more self reliant and resilient. And spiritual prep too... BTW -- these 1 world aspects are also biblical - for the very few that really understand biblical prophecy and not the planted false interpretations (i.e., 'Left behind' series smokescreen) which are found in most all the protestant churches. I grew up an atheist - but it was science that brought me to the bible. Sadly there are many false interpretations of scripture in the majority of churches (e.g., state of the dead: hell actually does NOT burn forever, and God's Sabbath is actually still Saturday which was kept by ALL the bible writers including Jesus and the apostles, and God has a last warning message (Rev. 14) which is a final test for those actually following God and keeping all this commandments. Time is short -- none of US can make it on our own merits. We have all sinned, and even one sin is enough to disqualify us and bar us from heaven. But Jesus paid the price, IF we will submit to His authority and let Him SANCTIFY us (Jesus said "you will know them by their fruits" (Matt. 7:16, 20) Heaven is a prepared place for prepared people. I can speak boldly on these matters because scripture and science all make it quite plain. And my delight is in pointing others to such truths while there is still time. Blessings - RH
Hi Clive, enjoyed the video as always...I've played with these for a while and perhaps the most interesting benefit you may have missed? Because they are microwave you can mount them behind doors/wood etc and detect motion the other side...try putting it under your desk (assuming no it's not metal) and moving your hand above. It will trigger...so making a detector than can be hidden behind wood or plasterboard may have applications in home security etc. Keep up the good work. Ps...if you mount it above the desk and move our hand below you may go blind!
I can remember TV engineers talking about waveform. Your mention of the curved edges reminds me of that. Billions of cycles per second don't care for corners. :-D
This circuit looks very familiar to the control circuit of a smoke alarm where there is a small amount of a radioactive substance sat in between two conductors, one going to ground or positive and the other to the chip, i think the chip measures the change in voltage in pulses.
11:33 -- The circular ring is connected to a constant voltage (V+), so it's at AC ground. It prevents signals in other parts of the circuit from affecting the voltage of the disc inside the ring. (It's a "guard ring".)
The transistor's collector (C) is connected to this ring / AC ground.
The disc inside the ring is connected to the transistor's base (B).
The S-shaped piece of PCB that's connected to the transistor's emitter (E) is a section of transmission line, which resonates at a particular frequency and which determines the circuit's frequency of oscillation. Since one end of the S-shaped piece of PCB is connected to the transistor's emitter (E), which is the signal source, and since the other end of the S-shaped piece of PCB is connected to capacitors which are connected to ground (so that the far end of the S-shaped strip is at AC ground), then the S-shaped strip is a 1/4 wavelength resonant section of transmission line.
There is feedback between transistor's base (B) and its emitter (E) through the space between the short strip of PCB ("stub") that's connected to B and the section of the S-shaped piece of PCB that's connected to E. The size of the space between that stub and the S-shaped piece of PCB that's connected to E largely determines the degree of coupling (feedback) between the transistor's base and emitter. The longer the space or the narrower the space, the greater the coupling / feedback.
So the circuit is a one transistor oscillator (specifically, a grounded-collector oscillator), having a resonant circuit that's connected to the transistor's emitter, and having some coupling / feedback between its emitter and base.
This guy said PBC multiple times, but assume that he meant PCB, printed circuit board.
Very well said! I have no idea what that really means, but then again, I know virtually nothing about electronics.
@@acmefixer1 -- You're right.
@@therealjamespickering -- The circuit generates microwaves. The microwaves are radiated by the little antenna. When something moves through the field of microwaves, some of the microwaves are the reflected to the antenna, where the reflected signal is absorbed, amplified, and combined with some of the microwaves being generated by the circuit. The result is a small change in the circuit's normal voltages, which the rest of the circuit (the rectangular chip) then detects.
@@kevinbyrne4538 Ok, that's much clearer, thank you! So the S-shaped track oscillates at a frequency of 3.18 GHz and the interaction between this and the disk attached to the base results in a certain voltage to be passed through the emitter? Movement in the room would then result in variations in the voltage?
Does the board only output a high/low digital signal, or is it an analogue signal that could be used to determine something about the size/velocity of the object?
Not an effin clue, but Big Clive's enthusiastic detective work draws you in and you keep watching.
@@N1gel Haha, I don't even know the basics of electronics, but I get drawn into these. I at least have an idea of which components do what, it's just the whys that Confused me, lol.
My list of questions never ends and at some point I will know more, but right now, I still love Clive's vids despite my lack of knowledge...the big surprise I was getting at you know, lol.
@@N1gel Nothing but respect for Clive. Techmoan and Explaining Computers are another couple of very good RUclips channels you might enjoy. :)
@@watsoft70 Glad to know I'm not the only electronics-noob in the audience. Whenever he talks about complicated circuits like this, I'm lucky if I can even follow along half of what's going on.
@@N1gel ... some things are just beyond the ken of mere mortals, and are not meant to be known the wot of. Microwave RF is clearly for wizards and other ethereal beings.
If Clive says it's complex it's really complex. Another really interesting video Clive thanks for all the hard work you put into these.
Glad I stumbled on your channel many moons ago, it fascinates me how all these things work and makes me want to get into making a few projects myself
If Clive says it's simple it's complex for me
One of the main textbooks on high speed digital design, not really RF, is literally titled “a handbook of black magic”
Loved this video! The fact that you tried to comprehend the magic of RF and still put out this video - the transparent film screen showing the back was a great way for you to explain of your thought train in a very slick way!. Always look forward to your new content, I’m pretty sure I’ve watched all your back catalogue :-D
As 50+ old fart it's been 30 years since I've thought about 1/(2pi*sqrt(LC)). You're video made my brain work - thank you.
Hehe, I also made those “simple” (slightly illegal) FM transmitters when I was young, most often with a preceding microphone amplifier, to become a small bugging device. Often choosing close to 88MHz or 108MHz, and then any ordinary FM-radio (preferably small and hand held) could be used as receivers. I learned then, that there was a big complexity to RF-electronics, since I put a lot of effort in doing very nice and clean builds, with often no good results, while a class mate made a very “ugly” build (blobby soldering, wires not cut close to the PCB etc) and that worked better than any of the rest of the class mates. It’s fantastic that a simple circuit like that actually ends up as a FM-transmitter. The simplicity to build things like this for FM an AM, together with the avast amount of existing equipment, is actually why I feel a bit “scared” that DAB will “destroy” the possibilities for future young kids, interested in electronics, to test and learn in an exiting (slightly illegal) way. Of course you can do a lot of MUCH cooler things today, with all sorts of micro controllers and advanced chips, sensors etc, but not at the same low level.
I’m glad Sweden postponed the switch to DAB. It really feels meaningless, since you could get the digital feeds via mobile data streams and the cost to switch all existing analog equipment would be enormous. It have played out it’s role... Keep at least some of the current FM-band analog (as well as the AM-band) as a backup system and for the kids to play with ;)
Btw, we soldered the antenna (normally measured to a quarter to the wavelength) to one of the loops of the wounded inductor.
My DAB radio failed fairly quickly so I'm still on FM. I wonder if the DAB time signal is still ~4Sec slow????
Appreciate these videos so much - truly, truly good quality educational content that is often impossible to find. Keep on keepin' on!
The Concentric Circles thing is the actual Antenna Element Back Plane . The Squiggle Line Track simply a Load Inductor doubling as the Antenna. If you measure the Distance between the Squiggle Track folding back on it's self you will find it a fraction of the actual operating frequency in .wavelength.. Probably 1/8th or 1/4 wavelength.
Agreed, as soon as I saw that I thought linear loading.
The rectangular track on the base pin will probably be 1/4 wave resonant stub too. Don't forget to account for velocity factor when working out the frequency, which is approx 0.5 on FR4.
@@Zadster LOL, That little Stub or Tab is most likely the primary RF Emitting Element. AKa Antenna.
Argh. I should read more before posting. If you think of it as a delay line one end is the frequency of the oscillator right now and the other end is the frequency of the oscillator a few pico seconds ago.
@@pulesjet I'm not so sure, given the electrically "large" area of the disc and the annulus.
This will be perfect for catching that ghost that keeps turning on my soldering iron after I turned it off.
id like to hear more about your ghost
I think I may have your same ghost...
Nah, that's just the ghost of Moss.
I bet it's the same ghost that switched my grandmas stove on and ran my water heater for 4 days straight.
If you manage to catch it, make sure it can't hurt anyone again.
@@uzaiyaro So leave the soldering iron OFF, ok Moss? 0188999...
This reminds me of a gadget I built before touch sensors existed. I used a PIC to generate PWM into a coil, which coupled with another coil. Somehow I could measure the phase between coils, which I put through an op-amp and back into the PIC. The theory was that my finger would change the phase. They laughed at me, said it can't work, but it did! I put two of these in a box and by sliding my finger up and down on the surface, I controlled a PWM fluorescent dimmer. Happy memories. My goal was to make a water-proof switch.
Isn't that how metal detectors work?
Nice one, well done.
@@Lasseu basically yes, my first touch sensor I made with a crystal, oscillator a few transistors, resistors, capacitors and a relay.
That's how inventions are made. Though a waterproof switch is much simpler to make, just get a reed switch and a magnet. That's how Nikko did their submarines.
Before touch sensors were around? Seriously? How about 1978 when I made touch sensors using CMOS 4011's? PIC's didn't even exist then. The circuit was simple, touch one spot to turn on and the other spot to turn off. Have to say though, the capacitance coupled sensor would definitely be better and could be made waterproof.
To paraphrase the late great Arthur C Clarke, microwave technology is indistinguishable from magic.
not sure if it was intended as part of the joke, but arthur c clarke was a radar specialist in WWII so I don't think microwave tech was very magical to him.
It’s amazing how such a simple circuit happens to be so complex. Thanks for breaking it down for us Clive, it’s much appreciated!
Hi Bigclive - really interesting video - I remember UHF/Microwave construction being described to me in the late 1970s as a bit like "plumbing" - the usual headache when designing higher and higher frequency circuits was trying to overcome and eliminate stray capacitance, but as you get towards the top end, they stop being a "problem" and start becoming an "enabler" - but you instinctively realise that :)
What's more interesting to see is that (compared to the tolerances within microchip fabrication) the relatively crude technology behind copper etching can be used to great effect.
It's a bit like looking at plans for a fairly crude valve amplifier and realising that the "cleverness" is all down to the physical construction, which we've all kind of forgotten with the ability to cram more and more components into an ever decreasing space to overcome design flaws
This is a perfect example of less being very much more :)
Clive, as a 50+ y/o electronics and radio enthusiast, may I say, if your video's were available when I was doing my training, I would be "up there" now, I really enjoy all your "tear-downs" and the way you detail your explanations. They come across so well. Even something like this complex uWave circuit. Well done.... You're a top bloke!
Sometimes I wonder what effect it would have had on my own learning if RUclips had been around when I was young. It'll be interesting to see how it affects the current generation. They have a lot of technical materials and tools at their disposal.
@@bigclivedotcom Yea, I'm so envious! One of my first "serious" books was a Ladybird book Making a Transistor Radio when I was about 10 - Remember the OC71?
This break-down caused me to realize that not every part of a circuit is either positive or negative relative to a connected part; but rather, the relationship can be more complicated; time-based or based on detection/externalities.
I was a broadcast engineer for a couple of decades, but RF was never my strong suit. I could keep big transmitters running, but I was way more comfortable with studio gear and computer stuff. I totally understand what you're saying!
This is a awesome talk on rf doppler detectors, the bit in the beginning which covers the oscillator and how one can modulate the amplitude is gold.
Love it, thanks Clive!
Where is the Signal Path god when you need him...
Just rig a microwave oven to run with the door open, if you smell pork, you have detected a body 😂😂
Oy vey!
*What the hell.. HAHAAAA!!!*
Oh my God man you hate the guy about to break into your house but don't give him cancer!!
Make sure and redesign your room to be the right size resonant cavity faraday cage. Make sure it is grounded. There, now your idea would work, but the sound of people screaming from sudden blindness would be your early warning alarm...
@Dave Micolichek So... it was effective at clearing the morning mind fog?
Back in electronics school, my teacher had been a elec tech for radios in fighter jets.
He told the story of a jet that would have radio troubles. After some time of trying to figure it out,, the E7 boss man, handed him a can of polish, and told him to polish the inside of the box the radio sat in...
It seems that the box was a capacitor in the circuit. ... hmmm
Well, the polishing worked,,, at least that is what we were told...
Thanks and keep up the good work.
I love these relatively long videos, it's a lazy Saturday afternoon, wife is having a nap with the little one and I can just veg and watch you explain cool stuff.
Some of your previous videos have given me great ideas for work projects too (Rpi/arduino stuff), so cheers for that too!
"veg"? Can I ask what "vegging" is?/
Amazing explanation and homework.. Especially because of the super zoomed PCB picture that was used. I'm sure it helped the viewers understand the PCB a lot more easily. Keep up the good work.
It may actually be more interesting watching Clive when he doesn't know exactly what's going on than when he does.
Preach :-D
I was on the development team of the C&K/Honeywell DT-7xx k-band Dual Tec microwave/pir motion detectors back in Y2K. I did a lot of GTEM work for rfi and international certifications and UL listing. That round pad pad on the with the positive ring could be adding a few pf capacitance to keep rf noise out of the transistor. RF can be funky at gigahertz frequencies. I watch your videos to jog my memory. My kung fu is old and haven't touched an oscope or frequency analyzer since 2004 working on Pave Paws. That was SLBM rocket science ;)
A hybrid coupler in ring configuration ("rat race coupler") perhaps. These couplers typically have four ports. Power input at port 1 splits and travels both ways round the ring. At ports 2 and 3 the signal arrives in phase and at port 4 it's out of phase and cancels. The reflected, out of phase signal (from your body) can be made to "unbalance" the ring which effectively brings one port to a higher potential than the other ports. Those eclipsed portions of ring might be the port couplings. Just a guess- I am not a µwave engineer (but have played with transmission lines in the past).
I like it and me too. C band satellite LNB pre amps when 120$ was entry price for a single NEC transistor with a much improved noise figure. Had no real business ordering those and resurrecting dead ones from lightning surges, but I was still more successful than not. Only thing I can recognize here is the quarter wave tank described as the only rectangular item on the board, hanging off the collector. 14:06 Those were very commonly used in that field for side by side coupling of the mixer signals. CRS about too much of it these days, but we are talking mid 80s too. End of the day, way too pricey for me to play and win.
Imagine all the time and research going into the design only to have it copied by the Chinese and sold for 70 cents a module.
I'm grateful that they broke out the 3.3v supply as well - used this in a project recently. Had no idea that the RF part was basically black magic.
A collaboration with the Signal Path is called for.
I think this is a voltage controlled oscillator, it doesn’t use a fixed frequency.
As others have said, the circular elements on the back plane are part of the antenna. For this sort of circuit to work the antenna needs to have an outrageously high Q, and ideally a pretty low radiation resistance, which a loop antenna provides. Essentially the ring looks to be a loop antenna acting mostly as a receive antenna. It’s coupled to to the transmit antenna with a sort of hybrid between a gamma match and a Patterson loop style capacitive network.
The 1k resistor and the two adjacent capacitors right before the sense input are an RC pi filter tuned to the oscillator’s stable frequency. When the environment around the sensor changes, the amount of reflected power and the phase of the received signal changes slightly, which causes a change in the circulating current in the receive loop, which causes the complex impedance on the oscillator output to change, which changes the oscillator’s frequency. The frequency change means the signal will move relative to the pass band on the RC pi network, changing the attenuation of the signal and altering the voltage at the sense pin, and the chip just triggers on the change.
If you have an RTL-SDR dongle or similar you should be able to confirm this by watching the signal in the waterfall. I bet it swings like mad when you sweep your hand near the sensor.
Clive, if you don’t have an SDR handy, I’ll order a couple and put it on the spectrum analyzer, and I’ll also send you a little SDR dongle. Super handy little gadgets for poking at RF circuits like this.
Indeed there's a github repo with information about this module (jdesbonnet/RCWL-0516) which mentions: "finally found the signal at 3.181GHz with the HackRF One SDR! One interesting observation: waving my hand in front of the sensor causes significant changes in the transmitting frequency, shifting by up to 1MHz"
Matthijs van Duin that’s interesting, I would actually expect the swing to be much bigger for it to be based on the changing attenuation of the band pass filter. 1MHz swing on a 3GHz signal would probably only be a fraction of a dB even at the steepest part of the filters curve. I wonder if it’s using the op amp that’s on the input of the chip as a phase comparator or something similar.
That blue battery usb suply make me think of another divice :-), Thumps upp as always.
What device..
Heh
Thumbs up where?
at 0.49 , he's also talking about bigger ones .....
Yes it does remind me a little of the "Should I stik this up my ass" video released some time ago.
Perfect timing, I just took delivery of 10 of these microwave detectors and haven't opened them yet! Cheers
Many years ago as i mooched around the local library I noiticed that a book enttled 'The Deadly Fuze' never moved. Eventually curiosity got the better of me and I took it out.Turned out to be the story of the development of the WW2 Proximity Fuze. Built into shells and fired up the barrel of a gun! And this was in the days of valves!! Can't remember the operating frequency but acorn valves could get up to about 500Meg. Used in anti aircraft shells and ordinary artillery shells.
And now we've got shells with GPS built in!!!
I bought some of these for a prank on my boss (we are in an office prank war... he started it... lol) and I wanted to know how it worked. Eventually I decided I’ll never know and that all I needed to know is that it did work. Fast forward 2 months and here I am watching Clive on an 8 month old video on the chips I bought. I have been a fan for two years, and somehow this is the one video I missed. Haha, thank you for this closure!
I bought two of these intending to use them as some sort of alarm, (instead of the LED you have) but did not do anything with them. Now I understand what's going on and can proceed further. Thanks a lot for doing this video and also thanks for the many knowledgeable comments from everyone.
The feedback from the collector to the base is in the transistor, mainly the internal capacitance between the collector and emitter. The square trace connected to the base is less an inductor/capacitor and more a delay line. The oscillator operates as a common base amplifier. The "squiggly" emitter line is a delay line. The disk of copper on the bottom behind the transistor is simply a ground plane. Some capacitance is there but it's unintentional. The ring of copper is the actual antenna. The ring and the disk ground plane act like a fresnel lens and makes the radar output more like a dipole antenna. When you move towards or away from the antenna, not only do you cause a doppler shift but you mainly case the frequency to shift (you're now part of the tuned circuit. At cm waves both are pretty much the same thing). The wiggly part of the emitter track introduces a delay from the frequency a few pico seconds ago and mixes it with the frequency that's happening now. In phase oscillations use less current than out of phase oscillations. The increased current drain for an out of phase signal is dropped and filtered by the emitter resistor (which is where the real feedback and transmit occurs) and the associated emitter/ground capacitors for detection.
@@pahom2 Everything is an antenna. In your case the dual squiggly lines is probably being used as an antenna and phase comparator. Remember that at these frequencies there is no real tuning inductor or tuning capacitor. Everything (including you) is part of a tuned circuit.
I was trying to figure out how the circiuts work (and they do very well!). Your video was the best and honest video I found! I highly (!) appreciate all the effort and time you have put into making this video, althought english is not my first language and I do not undestand every piece!
I think you are correct with the screening you spoke of. Back in my army days that screen was made of copper components and used to tune the device to see it's target.
Clive I think this was the best one yet.
Great work Clive..these videos generate thought, conversation and new ideas..keep them coming.
Gary in USA
that usb power bank is "DIRTY", cant even imagine what i thought it was when i first saw it.
hahahaaaa
You’re just an incredibly brilliant dude.
Old videos and new, I’m always blown away.
Did anyone else notice how Clive drew his own face in this video? - Just look back at the part where he draws the diagram of the P.I.R. sensor at the top of the sheet.... Now, tell me that's not a self portrait!
Thanks, Clive, for another truly enthralling video on something I know absolutely nothing about. - Give me valves (tubes) and high voltages any day. But, we shall learn........
your large format pcbs are a brilliant display tool. What an excellent presentation.
That RF oscillator could be used as the volume oscillator in a theremin. It would be interesting to attach an oscilloscope to the 'sense' point and see how sensitive it is. I might buy some of these and try to build a theremin.
The ring is a resonator at wavelength equal to its circumference. The top of the ring is pinned firmly to VCC by those bypass capacitors forcing that to be an E field node and the bottom to be an anti-node. The collector and emitter have opposite phase so that the meander line couples to the resonator on the back. Do those two vias on the disk connect to the base? They seem to be about -120/240 degrees away from the top standing wave node. Combined with the transistor characteristics and the base capacitor overlap, I predict this brings the positive feedback into phase with the resonator. Any Doppler effect shift will be f0 (v/c). That disk might couple to reflected energy so that the same transistor mixes those two signals with the 1k -- 1 nF forming the LPF to reject the carrier and sum frequencies.
I have some ceiling lamps I bought from Costco that I'm sure have this technology in them. I love when the light goes on when I enter a hallway. For the first 2 months, we all said thank you to the light every time.
My parents bought some cheap PIR ceiling lights recently. I installed on in the laundry. Its quite nice, except for the fact it has no sensitivity adjustment.... And I know I could change the sensitivity by swapping components. But the manufacturer has welded the damn thing shut. The only way to open it is by cutting it.
@@tin2001 The one I got has a remote and I think there's a sensitivity adjustment. Also the color temp, time it stays on, etc... Now if I could only find the remote...
I have a bunch of these and they are great, but I never bothered to try to figure them out, I didn't do very well in my RF and wireless classes when getting my degree. I understood diversity and multipathing, QAM and PSK, but for actually how circuitry worked and a lot of the math involved, not a chance. That stuff is black magic, to the people that really know it, much respect.
Thanks for doing the hard work. I ordered a bunch of these several months ago and plugged one in. It works! I just never got around to a tear-down.
I made these when I was kid too. I can remember my mother nearly feel off her chair when she heard me on the radio
I at one time worked on 45w 850mHz transmitters at the factory. I would tune the circuits be adding or removing silver solder from the copper patterns on the board. They were very sensitive to anything being moved around the power transistors.
850 millihertz transmitters must have needed a very impressive antenna.
@@stargazer7644 Not really. A 850mHz antenna is only about 6 inches long. These were for a early car phone system base station, before cellular phones.
@@oldmgbs2 - Star Gazer is busting your chops a little, for using the 'milli' prefix when you (presumably) intended the 'mega' prefix -- because a sub-1Hz frequency would (of course) need a hella large antenna :-)
@@theskett I didn't even catch that!
"m" for milli (1e-3) or "M" for mega (1e6).
Only accountants use "m" for million. Engineers and scientists use "M".
Clive’s got it right he could be an Electrical Engineer...
As my intro to EE professor said the difference between science and engineering is that engineers estimate, like Clive and his capacitor values being feasible, and scientists require exact values meaning they’re not as flexible dealing with real life components’ tolerances.
This also explains why most engineers are INTJ (me included) on the personality testing scale.
5:20 "The ZTX300 was also one." Instant flash back to Analogue Electronics in Higher Physics, 1986-7, where we had a tray of components and the transistors were ZTX300 and ZTX500.
Thanks for this. I bought a dash cam hardwire kit which is apparently a movement detector and it's so light I thought it was fake. All it had was one of these circuit boards. I now see that a tiny circuit is all it takes to make a microwave transmitter!
Im only a low level entry into RF circuits but I am aware in microwave frequencies an antenna called a discone is used most common. They tend to use a capacitive 'hat' and obviously get smaller the higher the frequency, so I think you have a very squashed discone antenna with all the relevant coupling components. The idea with RF is you want as much power thrown out as possible without any RF reflecting back down the feed to the transmitter or damage will occur. I know its very critical with high power outputs, but not so sure with very low power like this but it could have an effect if not controlled properly. It is called a discone because that is exactly what it looks like, a disc on a cone with an insulated separator between them. The disc is fed with RF and the cone is the ground reference and the size and angle relationship ( radius of disc and angle/length of cone with solid cone and disc or using rods as a cone and disc ) between them determines the frequency you want to transmit at. As mentioned by another commenter further down the receive parameters of the antenna will usually be compromised by a fraction of the desired transmit frequency ie 1/2 wave, 1/4, 1/8, 3/8 etc are typical because of size limitations on the board or your available space at home because the actual size required for a 1:1 transmitter in most cases would be far greater than the space available. Reception through an antenna does not need to bother so much with sizes of things as all it does is alter the amount of energy/noise/interference available to be received. In short, the antenna length/size must be a fraction of the wavelength of the frequency you wish to transmit at and the load on the transmitter device should be as close to 50 ohms as possible to prevent a dead short, because transmitting RF is almost a dead short and a lot of energy is at the transmitter in commercial antennas which is why you should never EVER touch a live transmitting element as you WILL get burned lol. With an AM/MW antenna the entire pole is live, ShortWave uses very long wires across towers and FM uses lots of types from yagis, log periodic, ground plane X shapes, monopoles, discones, dipole etc.. Basically the higher the frequency, the shorter/smaller the antenna length. Interestingly, behind those small to massive "snare drum shaped" microwave transmitters you see everywhere is just either a small discone, bowtie or dipole element in the center. The drum is just a reflector for line of site comms. :) Probably got some bits wrong but didnt want this to go on forever.. which it has lol
I'm using one of those microwave sensors as an under-monitor movement sensor. It is used to switch on an LED strip under my monitor when movement is sensed. The problem I have with these is that the sensing is patchy. They can often see me over the room (and through a wall) but will often not detect when I'm sitting at the keyboard (2ft away) moving my hands about the keyboard and to mouse etc (1ft away). My current solution is to have one under the monitor looking at me and another blu-tac-ed under the wooden desk and mousepad.
I've never yet worked out the front/back of the sensor to find the most sensitive side. I've been tempted to try a PIR sensor on the monitor instead but never got around to trying yet.
It may help to extend the run time so that the occasional detection restarts the timer. I use an outdoor PIR unit on my bench lights.
i just did a thing of which i am inordinately proud. i bought a bunch of these, and decided 3 secs was too brief for the output signal. so i found the data sheet, learned to solder 0603 smd bits, removed the 10nf timing cap, popped a 100nf one in it's stead, and voila! it now switches for 30 seconds...and for my next trick, i just ordered some arduino nano PCBs and all the bits on the BOM. i am only going to try and make my own 'arts and crafts' arduino nano! and a mere year ago i was horrified by the thought of even soldering the headers on one. i learned it all from watching YT vids.
I once worked in a firm that was involved in microwave sorts of things. You can make a tuned circuit by drilling a hole in a bit of metal and putting a plate on either side. That's your inductor and capacitor right there.... Also wave guides are a lot like plumbing just very precise.
Well you did a fine job splaining it, I was lost but then caught up. Flooded kansas again. Rain for the last 5 days. Supposed to be sunny tomorrow. Cheers.
Send the rain to Australia... We have drought where I live.
@@tin2001 done, if you can send me a 545rfe transmission for the truck I bought. I'm driving myself crazy not being able to go out and finish pulling it, make sure its what's wrong.
Clive, you should get your amateur radio license! So much RUclips potential!
Fascinating..Ive just bought an outside floodlight with microwave sensor from CPC, havnt put it up yet and wondered how it worked compared to PIR ..Thanks Clive :)
Great work Clive. Embedding these in a timber staircase to identify individual steps. Then to trigger LED lighting.
Something to consider might be piezoelectric disks to detect physical step contact from underneath.
Great to watch you second guess what and how the designer was trying to achieve. There must be a bit of detective Columbo in your DNA. One more thing....
I was impressed I have ordered 10 from Ali, @31 pence each, it's crazy that you can buy something so clever for so little.
With a high enough operating frequency a circuits behavior becomes indistinguishable from MAGIC.
I feel like I should be getting course credit for this. Very nice video!
if you pass the quiz...
I think of things like this as engineers taking physics and breaking its back over their knee. In ten years it will probably be taught to 14 year-olds and be considered just normal everyday stuff. I love watching the way technology, behind the scenes, is advancing with quiet, almost, unnoticed, steps.
Thank Clive for the excellent video.
I love RF circuits , thank you Bigclive
Microwave RF design is something magic. As I'm not a wizard I don't understand much of it. As a ham radio operator I want to work on the GHz bands as well some time in the future.
The magic fades pretty quick once you start mucking around with it. Go on AliExpress, lots of little SMA-equipped modules to play with.
its the RF "skin effect" that makes this so mystical
EXCELLENT Video BigClive, once again you bring us mere mortals outstanding, interesting and simply awe-striking photo overlays with sublime PCB Exploded views, thank you immensely
*claps hands* Yay! A new BigClive video!
- And I just got my first meter, and a PCB holder 😁
Double yay!
... now to figure out how a meter works, while I wait for a kit that'll teach me the basics 😂
*looks at wall outlet*
Congrats on getting on the road to start learning electronic. Do not do what I did with my first meter and a wall outlet: I tried to check if neutral was really connected to ground by measuring the resistance between both, I was lucky as it only damaged the resistance range I was using. It was a passive analog meter, I'm not sure a modern electronic meter would fare that well.
@@SlyPearTreeThanks!
And that sounds like an exciting moment! Haha
Kinda sounds like a thing Clive should test out, while demonstrating to us (not you included ;) newbies how a meter _should be used_ and *not* used 😂
I'm still tip toeing around and reckon it'll be a good while before I start dabbing with the mains (So for others; yeah if it wasn't obvios, I was kidding xD).
Rather safe than sorry in this scenario 😁
You’re on your way! In 30 years you’ll look around and wonder where all the electronics crap you’ve collected came from!
Slypeartree a proper modern meter should not be damaged by that. That’s actually one of the tests Dave Jones on EEVBlog does when testing meters - full mains voltage on resistance range. Some fail spectacularly. Older analog meters will release the magic smoke and possibly detonate the battery.
@@stargazer7644 *giggles* Since I still have my childhood SNES I hate to imagine where I'm at when I hit 60 😂
- Thanks for the feedback!
FYI: I did test out my meter on a diode and after some fiddling around (It's an 'automated' meter; probably should've picked a conventional one instead) it, to my amazement, worked.
Let China be praised by the sun,... for their cheap electronics! 😁
Thank you Clive, a very intriguing, detailed explanation. It is fair to say that I need to watch this many more times before any information permeates into my brain (and is retained). Thank you again; you help me enjoy learning (slowly).
RF is firmly in the category of rocket science, so don't worry if it doesn't make sense compared to "normal" electronics.
Clive, thank you for teaching me about this device, I've had one in the drawer for quite awhile now. I think i will temper with it's C-TM with resistor and maybe short it out. What i really wanted from this device was the magnitude or perhaps frequency of detection and not so much staying on for a duration.
That may switch it on permanently. Adding a resistor reduces the resistance as it will be in parallel with that inside the chip.
yet another great vid, always wondered but assumed it was short range radar. the eclipses you talked about, in my experience ... the capacitance is used to tune an antenna wire or in this case the track. for example the 2.4ghrz band ( most wifi traffic and bluetooth ) and the antenna shape and reflectors on the back help with beam forming ( rf shaping or direction ) so... 300 (reference to speed of light acepted figure for antenna calculations) devided by 2400mhz known as 2.4ghz will give you 0.125 of a meter or 12.5cm ( the required antenna electrical length for 2.4ghz) which can be shortened by introducing a week capacitance to allow the physical length of the antenna to be reduced to make it more manageable. most modern antennas are designed this way to reduce physical length without disturbing antenna performance or in some cases actually enhance it. hope im right and this helps.
You're not wrong. Track width and capacitance values of mere picofarads or the reluctance or inductance of micro-henrys, can make a large difference in resonant frequency... Very careful design of layout track width, path and component values are critical... That's why RF equipment has so many variable Caps and tunable coils....or you'd never get an accurate or stable frequency... Tuning RF equipment is an art in itself.....
Peace, Keith......
Pretty clever. You really gotta stare at it to see all the layers. The single transistor is being used for several things at once. The base is capacitively balanced between the TX and RX in such a way that if they don't cancel each others opposing capacitance charge the difference will change the bias of the transistor. A lot like how a phase lock loop can demodulate FM. It's seems a lot like just a microwave frequency version of a phase lock loop metal detector that's been cleverly manipulated out of a single transistor and some passives. The metal detector doesn't beep unless you swing it, but in this case the coils are stationary and the metal moves. The higher the frequency the more the water in the soil reflects back on a metal detector. That's why they only use around 7khz.
Clive it’s a good job I love the sound of your voice because despite really trying I didn’t understand a f*cking thing tonight.
Thanks for posting anyway though I really appreciate the hard work you put in to educate the masses.
I assume the disc and ring are a circular or spherical polarised antenna. The FPV community might say it looks like a linear 5.8Ghz patch antenna with a ring around it. There are many designs of FPV microwave aerials, some appear to short the signal to ground (usually with a twist or three) while others are capacitive - an interesting one which is circular polarised and can be printed cheaply on discs of PCB. It was provided open source by RF legend Maarten Baert. It's currently the most popular design www.maartenbaert.be/quadcopters/antennas/pagoda-antenna/
It would be interesting to grab a load of these detector boards and try overclocking the range using higher voltages, enclosures, Pringles tins etc... Great video as usual Mr Clive!
Just mount one at the focus of your satellite antenna.
No. A simple ring does not give circular polarization.
@@graemezimmer604 You're right. It's probably more like this design www.maartenbaert.be/quadcopters/antennas/triple-feed-patch-antenna/
I used to make those FM-band transmitters too-- circa 1967.
In those days we could buy "Poly-Paks" transistors, basically floor-sweepings. But they were perfectly usable 2N706's, 3 for $1.
You could put a crystal microphone onto the base and pick up the signal and sounds for a dozen feet or more. Fun times. It was legal in the USA at power levels up to 50 milliwatts and 3 feet of antenna.
You have some base-emitter feedback there.
On the note of the "intelligent" powerbanks that shut off... How about a video about modifying them to either not do that or turn down the current they require to be drawn to stay on, if possible? I've had tons of projects where I thought "I could just use a powerbank to power this" and then these "intelligent" ones ruined that idea, especially ones that require something like 200mA minimum to stay on. There's simply no way to use low power stuff like a simple 1 LED light (ikea jansjö USB for example) with long runtime in mind from it because the powerbank will just turn off after 10secs :(
IIRC, you can change the value of one of the capacitors to prevent that behaviour.
Check out Mr Carlson's Lab RUclips channel.
If you ever get interested, I'd love to hear your explanation of mass spectrometers and the quadropole mass selector. They're all about how alternating electric fields interact with ions of different masses.
A fair amount of that went over my head, as the actress said to the bishop!
Hey Clive, what an interesting circuit. And what you call a `cheap and tacky' meter has been my main meter for about 15 years, so reliable. LOL
That blue vibrator is also a power bank! That's kinda innovative.
Horrible idea. Just imagine it failing violently while in use...
@@AttilaAsztalos See also: Fanny Flambeaux
The mode which always resets before triggering again is useful when you're doing the on/off timing externally. This way the external circuit can continously detect movement.
Or if you want to scare deer in your back yard by flashing lights at them in odd intervals.
If you hook up these to a ardunio and solder a wire to the analong input of the chip (I'd have to look which one it is as I don't remember) You can also get reflection intensity on a graph via the serial monitor with a little programming. Put a couple of these on a parabolic dish and you have a low power radar!
could this help to isolate false positives from plants/leaf movement?
this was jolly interesting. for several reasons. today i bought, for a quid, a crappy thing consisting of a fake cork, with 3 button cells in it, and depending from it are 2 lengths of wire, between which are soldered smd leds. it is intended to be put in an empty bottle. i bought it to play with a microwave motion detector. the amusing bit is when i walked in asda, with the device in my pocket the security alarms went mental! and then in Sainsbury's and Lidl too! i can only assume the lengths of wire, which were tightly wound in coils in the packet had an inductance which was able to take a charge from the security gubbins EM field. fascinating. i actually came here to discover which is the front and which the back of my micro-wave pseudo IR jobbies. i couldn't work it out as they seem to detect motion anywhere.
To make them directional they have to use a screening plate behind them.
What Leon Theremin was trying to develop when he accidentally built a musical instrument.
Some motion detectors used in security/burglar systems use both a PIR and a microwave detector (called "dual-tech" in North America at least). Both sensors have to detect/trip in order for the zone to be considered violated, which greatly reduces false alarms.
Always fun to see what other engineers work with, very interesting.
The big track on the base is coupling to the tuned circuit on the emitter. That is positive feedback so it oscillates.
The oscillator circuit is probably common collector. The feedback is from the emitter to the base through a transformer to get the required amplitude increase. Since the collector is grounded, the collector to base capacitance becomes part of the tank circuit and the Miller effect is eliminated. The transistor can then operate at the highest possible frequency.
BISS0001 chip is special for PIR controller (Passive Infra-Red), but you can modify this chip into another sensor controller like in this video the chip as a micro-wave proximity sensor.
I think the capacitor/trace array is forming something similar to the old ladder line, which is in effect a series of tank circuits. It allows an antenna to be resonant at an improper dimensional characteristic. In effect it's a microwave transmatch to make use of the PCB as combination resonant body and RF emitter. It's been a few years since I was too deep in this stuff, but that's my take (subject to correction) on the oscillator/transmission line/antenna you have there.
The presence of the human in the vicinity of the RF field detunes the whole affair, triggering the off delay. It's a lot like a Dip meter.
Back in the late 70's this was used for some alarms. Heathkit had one I built for a friend's TV shop, and it had a discrete telephone dialer in it as well, which you set using dip switches. Once triggered, the dialer would use a reed relay to dial your home number (programmed by the switch array), then you would have an open mike in the room so you could listen to the people stealing your stuff.
No, just no.
Clive - I finally figured out what you meant. I can use the 3.3VDC Hi circuit to close the ground loop for the camera's dry input.
It took me a month. I feel slightly dumb. :)
6:20 pirate radio was such a cool thing...I’m sure a lot of smaller pirate stations used similar designs!
I've used them as movement sensors in a few motion activated arduino systems. One thing of note (apologies if others have already said this) is they seem to work on detecting motion of fluids (bearing in mind the human body is mostly water). You can prove this by first waving an empty water bottle in front of it, then waving a full water bottle.
Wonderful 🎆🎇🎆🎇 As an EE schooled in the 70's - designing these types of RF circuits was referred to as 'black arts' - it is very specialized to the point of being black magic. Now with computer modeling, it is likely far more 'controlled' design, but still so amazing. Wonderful breakdown on it and loved all your visual aids - appreciate the time and effort required for all this.
I have been toying with the idea of these for a security grid on our remote property.
=== All should be getting ready -- as in the forming of this arising 1 world totalitarian state - they will crash food supplies, energy, economies as part of the 'great reset'. So the prudent will Stock food, water and energy, barter items, and overall become more self reliant and resilient. And spiritual prep too...
BTW -- these 1 world aspects are also biblical - for the very few that really understand biblical prophecy and not the planted false interpretations (i.e., 'Left behind' series smokescreen) which are found in most all the protestant churches. I grew up an atheist - but it was science that brought me to the bible. Sadly there are many false interpretations of scripture in the majority of churches (e.g., state of the dead: hell actually does NOT burn forever, and God's Sabbath is actually still Saturday which was kept by ALL the bible writers including Jesus and the apostles, and God has a last warning message (Rev. 14) which is a final test for those actually following God and keeping all this commandments. Time is short -- none of US can make it on our own merits. We have all sinned, and even one sin is enough to disqualify us and bar us from heaven. But Jesus paid the price, IF we will submit to His authority and let Him SANCTIFY us (Jesus said "you will know them by their fruits" (Matt. 7:16, 20) Heaven is a prepared place for prepared people. I can speak boldly on these matters because scripture and science all make it quite plain. And my delight is in pointing others to such truths while there is still time.
Blessings - RH
Hi Clive, enjoyed the video as always...I've played with these for a while and perhaps the most interesting benefit you may have missed? Because they are microwave you can mount them behind doors/wood etc and detect motion the other side...try putting it under your desk (assuming no it's not metal) and moving your hand above. It will trigger...so making a detector than can be hidden behind wood or plasterboard may have applications in home security etc. Keep up the good work. Ps...if you mount it above the desk and move our hand below you may go blind!
When I first tested the Doppler lamps they would repeatedly trigger if it was stormy outside. I guess they may have detected tree movement.
@@bigclivedotcom I wonder if the sensor is detecting small amounts of microwave radiation from (even fairly distant) lightning?
I can remember TV engineers talking about waveform. Your mention of the curved edges reminds me of that. Billions of cycles per second don't care for corners. :-D
This circuit looks very familiar to the control circuit of a smoke alarm where there is a small amount of a radioactive substance sat in between two conductors, one going to ground or positive and the other to the chip, i think the chip measures the change in voltage in pulses.