Quite against the opinions of most people here, I am glad Julian took the time to show us how to confirm that it is a buck converter with conventional tools. Not everyone hat a Scope. So by using your Brain and a Meter you can now conclude what the truth is. Thank you Julian.
There are people convinced that have created free energy machines by using the wrong tools and coming to the wrong conclusions about their observations. Even people with good electronics knowledge can mistakes around the operation of reactive circuits when they make assumptions.
That was a great tutorial! I'm amazed the efficiency was as good as it was. I was thinking the inductor was gonna be too out of whack to be really doing anything other than PWM. I love your explanation too, it was really good. Thanks.
Julian, your work is excellent. It is well presented, well explained and you don't show off with loads of high tech kit that the rest of us can't afford. Well done sir!
Nice explanation Julian, It's clearly a Buck Converter with very simple components, in a good and cheap pack it could be teached on schools along with the Ohms Law. Thanks for the video!
Next thing to experiment with is the strength of the inductor - see if you can improve the efficiency by varying the number of turns/size of the torus. IIRC, from my school Physics, the standing wave collapsing within the torus is also influenced by its physical size. Interesting times, Julian.
At 6:00 -- shorting out the inductor makes the bulb brighter precisely because you're doing buck conversion. With the inductor shorted out (PWM), at a 50% duty cycle the bulb would be 'on' at full power for half of the time, drawing 50% of full-duty-cycle power. With buck conversion, however, at a 50% duty cycle the output voltage is half of the input voltage. That implies that the power drawn by the bulb is 25% of full-scale power (V^2/R). A bulb drawing 25% power is going to be dimmer than one drawing 50% power.
The resistance of a filament bulb is very temperature dependant Driven at half the voltage it will take more than half the current because it has lower resistance. The buck convertor does not "double the current" when it halves the voltage. It doubles the available current. The actual current flow will depend on the impedance of the load among other things.
Julian, The fifth pin on the transformer is there so it can only be placed in a circuit board one way around. It has no electrical connection. Thanks for the videos. :-)
If you want to crimp that sort of terminal with pretty much any pair of pliers, put it between the handles, all the way up there. Does the job quite nicely, that does...
the light bulb changes load when given different inputs so that was not as conclusive as it looked. You need to use something less reactive as a load, like a low temp coefficient resistor.
Nicely done Julian! Very good demonstration that it is, in fact, actually doing buck conversion. You could of course use the information that you got from the ammeter and the voltmeter to compute the efficiency as power(out) / power(in). You had ~ .144 Amps at 10V, on the input side, and ~.190 Amps at 5V on the output. Since power is voltage * current, the efficiency is (10*.144) / (5*.190), or about 66%. Nice.
Great stuff. I had sort of wondered if the pwm was doing all the work but i knew that the buck had to be doing at least a tiny bit. I figure they ultra low efficiency your seeing here is due to the inductor. It looks as if that inductor might be better suited for 500khz or more, maybe even into the tens of mhz. You also mentioned it may not actually be a very good square wave which will be interesting to see on the scope for next video. If you can crank up the PWM frequency, or drive the mosfet directly from the sclk on the MCU, That would be really fun to see. Cheeerrioos! :)
I would guess that the lamp gets brighter when the inductor is shorted because the power dissipated in the bulb is V^2/R. With pure PWM (inductor shorted) you get bursts of full voltage, whereas with the inductor in circuit, the voltage is reduced---so you lose out from the V squared term. (The R of the bulb does not change very much.) (I would also be very cautious with current readings in PWM mode.)
Nice update Julian. I wonder if anyone dares to criticise this time :-) I'm still a fan of the lamp, and the reluctance to grab the expensive tools to prove what's going on. So many don't have access to them. Oh, and I'm guessing the noise you heard from the soldering station was a loss in the step down transformer. Was that all planned? :-)
Adam Welch challenge accepted: I am still not sure how to pronounce his last name and he talks with a funny accent...only cause Adam dared me. My biggest serious critique is TAP that bolt out man! I know it's driving you crazy too, I know it is. Also, I have a bunch of cores and magnet wire if you want to wind your own inductors too...I know you did in a couple videos back but didn't have the large toroids, I'll send you a handful, just let me know. I'm going to have a bit of fun replying to some of these comments.
The simple fix for this is to add a large cap across the output. That will hold peek voltage and if you are then getting dimming still, then the buck is definitely working. You could also control it with a 555 astable with pin 5 as the mark space control. You'll have to use a separate supply for that s using an nch fet there makes it complicated.
Julian, I really like the way you handle the difference of people's understanding...you calmly and methodically work through the circuit to show what really is going on and how it works. Never taking criticism personally (I wish had your patience), you make a wonderful teacher. Thanks again for your video.
I would say, no feedback to complete the regulation but it is definitely a bulk dc-dc. Capacitor is needed to smoothen the output but with that not in place doesn't mean it is just a PWM.
Please do the oscilloscope test! =) I'm pretty excited to see the results. Would it show massive ripples? Small high frequency ones? Or Would it be as clean a battery? =D
I enjoyed this video. It's been decades since my circuits classes, but you remind me of one of my favorite instructors. Have you ever done a "black box" analysis of a circuit? I.e., there's a circuit in a black box and the goal is to figure out/recreate the functionality of the circuit without looking inside.
Hi Julian, You could just understand that this circuit is a buck converter or not by changing input voltage and you could see the output brightness should stay same.
There is a defference betweeen ac and dc there is no ac in this circuit. Ac change polarity between the two wires. Actually what we have is pulsating dc so it's a dc to dc converter. If you put a cap on the output the voltage and current will remain the same, however if you take off the load the voltage will rise as it charge the cap. You should remember it's the pulse width that cause the voltage drop it's still the 10 volts switch, so with no load it will say 10v on the output. But then again Julian say it's not regulated so the circuit is working as it should not the most efficient but it works.
I think it would be a better demonstration, if you put the diode reverse biased where the inductor is, and the inductor in the place of the diode. We would then be assured that the power supply wasn't lighting the lamp and the power was actually being supplied by the inductor.
hi Julian I hope you don't mind me contacting you but I have query I need a little help with im currently in the process of building an hiland 0-30v power supply that I am fitting into a nice case so I am changing the 2 pots for a nicer range of voltage but I got 2 5k pots instead of 10k pots by mistake what I need to know is what difference would it make to the power supply using 5k instead of 10k pots cheers peter
arif anwari No. The resistance of the wire of the inductor will be fairly low, in fact most likely lower than that of some of the connecting wires that he is using.
Julien, i was wondering on these digital controller part of the power supply, there are terminals for VCC, xD, RxD, grnd. Can a bluetooth interface be hooked up, or something else, if not whata it made for?
Julian, in your next video in this series, could you spend a moment or two talking about why it does or does not matter that the 0 volt lines are not tied together in this circuit? Ta.
Mark 1024MAK I am not really sure, hence the question. My thinking is that the 12v supply coming in from the left is from Julian's Lead-acid battery array, has a 0v line that is independent of the Uno's power supply. There is some sort of voltage being supplied to the gate of the n channel MOSFET on the top left of the main board, but for that signal should be somewhere above the 12 volt supply to turn the MOSFET on, so I assumed that the signal voltage should be referenced to the same 0 volts as the main board, but there does not look to be any kind connection between the 2 zero volt sources. In other electronic projects that require different voltages eg a 5v and 12v supplies, there is usually a single 0v rail that both these voltages are referenced to. I am still unsure so if you or Julian could discuss it ( I would prefer J himself personally as I find his style of explanation very accessible) then I hope to learn a bit more about the finer details of this project. Hope this helps with understanding why I asked the question. Ta
I just realized something. How do I power my buck converter? I need to step down 54 volts (e-moped battery) to 12v max 10 amps. So I am looking arround and sadly many youtubers fallback to the 2576 whicg cannot go high enough and is only 3 amps. I I really want not go the arduino way and you do a great job! But how to power my arduino from that 54 volt battery? Right now the only thing I can think of is to use a lightweight buck converter (I have several XL7015 based 80 volts / 0.8 amps buck converters) but it feels a little silly?
Hello Julian Ilett, greeting from Indonesia! Currently, I try to build my buck converter, sadly I haven't succeeded in converting down the input voltage. If you don't mind could you please tell me about what kind of or what type of PWM driver that you used in this video? your help means a lot to me :) Thank you in advance!
Question for you, Julian... If you take a 240-24V AC-AC transformer and connect its secondary side to the secondary side of a 240-4V AC-AC transformer, how many volts would you get on the primary side of the second transformer, and would you dare touch the leads with your fingers on one hand? I don't think doing it with fingers from both hands would be a good idea, though...
You would over saturate the core on the second transformer and it would basically become like a short circuit on the first transformer. It might work a little bit but you wouldn'tget the high voltage you were expecting. Sorry.
Wouldn't you need to include negative feedback in the controller? So the knob would set the voltage target, and the Arduino would increase or lower the PWM duty depending on if the output is above or below the target voltage? The output voltage will be different depending on the load otherwise.
A bulb is somewhat self-regulating. Higher current, higher temperature, higher resistance. It's not very good regulation at all, but it''s good enough for a simple testing situation such as this.
What about feedback with constant voltage output with some sort of voltage divider... Then feed that back into the Arduino as some "feedback" voltage divider type circutry.. regardless if it's pwm or not, ... works either way I'd think. Good video. +1
I believe 30kHz ripple in current meter will be causing measurement error. As many have already said "Add a 100uF" capacitor across input AND output output to give you DC with minimum ripple. Then meters will read accurately. With capacitors added the difference between PWM and BUCK will then be easily seen when shorting inductor!
Two capacitors each side. You're dealing with square waves here, so there can be some really high-frequency components involved. Electrolytic caps have poor ESI, so the usual approach is to use an electrolytic and a lower-value, lower-ESI capacitor in parallel.
Vyl Bird Do you really think adding small capacitors (100uF and a smaller non-electrolytic type) will make any significant difference given that the load is a current hungry filament lamp? The answer is NO.
ESR of 100uF is around 0.3 ohm. Lamp resistance is around 5-10 ohms so 100uF will take over 90% of the ripple current. If current meter monitors lamp current only (not capacitor current) then its current will be mainly DC.
Hmm... makes me wonder how that circuit would behave if that inductor is replaced with a ceramic capacitor similar to the solar PWM circuit that you built a while ago :)
tbbw The lamp may (or may not) light very briefly (depends on the size of the capacitor, a ceramic would be far too low a value, so the lamp would not light at all), but would then go out and stay out. As the capacitor would charge up when the transistor is switched on, but it has no discharge path, so once fully charged, there will be no significant current flow through the lamp.
Just tell me please why is the current in the "secondary" side higher now? My guess inductor drives the charged up (remembered) current when the switch opens (knowing the current slowly decreases of course depending on switching frequency and in inductor value) instead of just being zero if the switch opens - so therefore just increasing efficiency??? And now assuming your A-Meter (which looks great ;) does a little bit of averaging (maybe filtering?) the overall measured current is now higher in the "secondary" switching side.? Please tell me i am somehow right i graduated not so long ago from electronics .. but buck and boost converter well these things i have to and i really want to understand fully & truly.
My way would go as far as to measure the current in the secondary side with an oscilloscope and to see the current when Switch is open as well as closed
Take a 1 ohm resistor supplied at 2 amps for 1 second and 0 amps for one second, an average 1 amp. So using averages gives 1 amp times 1 ohm ie 1 watt dissipation. But power is current squared times resistance so it's actually 4 watts for one second and zero for one second ie 2 watts average dissipation. That's one reason why people buy RMS meters.
Why don't you just view the output with your scope to measure the peak and average output voltage, if it's a buck it will be lower, if it's just pwm the peak will be the same as none buck and non pwm.
The lamp brightness isn't an indicator of the voltage at the load, but of the average power (and thus average voltage and current). But what we want to see is the output voltage being more like a DC value than pulses of 10V and 0V. All your measuring devices in this video will be averaging internally, so we're not seeing the truth. All switch-mode supply experiments *need* an oscilloscope!
Well I enjoyed that, I usually just use recommended circuits from datasheets for buck or boost ICs so it is nice to see you homebrew something yourself. Still, this comes from a self admitting noob.
I like how you've gone for the clever approach of looking for current step up to show it's more than just PWM rather than getting the scope out. However I would struggle to put my faith in your current readings bearing in mind the likely very large and high frequency voltage and current ripple. The accuracy of the readings could be affected by that. You will need to just get the scope out and show some voltage and current waveforms. If you want to prove your claim that it's a DC to DC converter, show a DC output voltage. Of course the simple explanation of a buck converter which is ubiquitous in the hobbyist community (which I don't like because it doesn't account for the current step-up and can't be adapted for boost and buck-boost converters) is that it's a filtered PWM, so then if you take that definition you're really arguing if it has to be an LC filter or if your LR filter counts (R being the lamp and the lamp also being the load). Of course you could just add an output capacitor and then nobody would argue that it's not really a buck converter. That's all it's missing. (I think you're correct in that regulation isn't mandatory for the definition of a buck converter, just unregulated buck converters are of very limited use).
Pohan Huang the mosfet is being switched by the Arduino using PWM, presumably the NMOS has a low enough gate threshold voltage that it can be switched by 5V from the Arduino.
What i don't understand is how the bulb gets dimmer, even though it consumes more current. Can someone please explain? I feel like i am missing something...
muh1h1 its because that arduino current meter is not an instrument but a toy. On each cycle the current will ramp up steadily if inductor is present but that toy will sample randomly. So the reading you see there is actually not the actual current. Its a playing with kind video so dont try to find justification
muh1h1 The lamp does not consume more current. The energy from the supply is converted from a 10V voltage supply to a lower voltage supply. If the supply to the lamp is 5V, then as energy cannot be destroyed (it can only be converted) less current is drawn from the supply compared to the current to the lamp. When the switching element (transistor) is off, the magnetic field in the inductor reduces, and current flows through the inductor via the diode, that same current goes to the lamp.
well I didn't say that's not a buck converter. I said the effect is like a pwm. I suggested that you should measure current to show the current gain. And you did but I think you should have put at least minimal effort to filter the output a bit - just any >=100 uF capacitor
Everyone knows that PWM is the most prominent way to switch DC voltages right? Like that's the way you do it, so if all you see if PWM, he's done it correctly...sure you can use a simple voltage divider or a voltage regulator IC but neither of those methods can handle high/ large current. Just because he's powering it with a small adjustable DC load here doesn't mean he can't put 4 batteries at the Drain and do the same thing. This is exactly what you should be doing it so grab an old computer power supply and try it yourself...then you'll have an "Adjustable power supply"
Hahaha, you'll never live down the displaced terminal in the top left, will you? That aside, you mention at 12:45 that the brightness of the lamp is sufficient as an indicator. You'll remember that this only works for instantaneous changes. For anything else, I wouldn't trust your video image further than I could toss you courtesy of the unscryable influence of your current daylight and your camera's exposure control. Cheers!
I'm happy to have been proved wrong it's certainly not the first time. I was worried you had joined the free energy nut job fraternity that make big claims based on no evidence. I begrudgingly admit you may be correct LOL. I would still like to see the scope traces, but more excitingly I would like to see it running closed loop with the lamp staying at the same brightness as you vary the input voltage. I assume what your driving it with has an analog input you could use to modify the PWM. Best regards Chris
These videos come out so far apart these days that I think Julian will be on reduced income this month. Next time you are screwing terminals in tight hole just add some oil so the wood doesn't clamp(stiction - sticking friction) on the metal.
Hi Julian, thanks for this vid! I'd really like to see you explain the physics of the inductor. How it is that it 'stores' current/voltage (difference which capacitance). Some chat about the circularity of the flow, dynamics of the fields effects on itself's coils. Why it is that voltage/current changes.
Mark T Inductors (all types including transformers) store energy as magnetic fields. A change in the current flow causes a change in the magnetic field. When you switch off or reduce the "input" current flow, the magnetic field reduces, which induces current in the windings.
emmm.... i won't say DC-DC buck is exactly the same as AC-AC step down as its primary and secondary coil are totally electrically isolated from each other and whats actually causes the creation of lower voltage is the magnetic flux cutting the high permeability core in most cases iron core is use which faraday law applies. DC-DC buck in another hand has no electrical isolation involve where the high "magnetic charge" in the choke release and converts to electrical current at the last direction of flow during 0V.
Quite against the opinions of most people here, I am glad Julian took the time to show us how to confirm that it is a buck converter with conventional tools. Not everyone hat a Scope. So by using your Brain and a Meter you can now conclude what the truth is. Thank you Julian.
There are people convinced that have created free energy machines by using the wrong tools and coming to the wrong conclusions about their observations. Even people with good electronics knowledge can mistakes around the operation of reactive circuits when they make assumptions.
Coolkeys2009 what? Free energy? What? Lol...
A very thorough investigation, very informative, thanks Julian.
That was a great tutorial! I'm amazed the efficiency was as good as it was. I was thinking the inductor was gonna be too out of whack to be really doing anything other than PWM. I love your explanation too, it was really good. Thanks.
Julian, your work is excellent. It is well presented, well explained and you don't show off with loads of high tech kit that the rest of us can't afford. Well done sir!
Nice explanation Julian, It's clearly a Buck Converter with very simple components, in a good and cheap pack it could be teached on schools along with the Ohms Law.
Thanks for the video!
Next thing to experiment with is the strength of the inductor - see if you can improve the efficiency by varying the number of turns/size of the torus. IIRC, from my school Physics, the standing wave collapsing within the torus is also influenced by its physical size.
Interesting times, Julian.
At least you have proved that it is working as a Buck converter.
Gotta hand it to you. Stepped up to answer the nay sayers. Good job.
Love the way this turned out - excellent experiment and learning opportunity!
Holly cow I would not be able to keep track of all the toys you have I would forget what they are. Good job explaining
At 6:00 -- shorting out the inductor makes the bulb brighter precisely because you're doing buck conversion.
With the inductor shorted out (PWM), at a 50% duty cycle the bulb would be 'on' at full power for half of the time, drawing 50% of full-duty-cycle power.
With buck conversion, however, at a 50% duty cycle the output voltage is half of the input voltage. That implies that the power drawn by the bulb is 25% of full-scale power (V^2/R).
A bulb drawing 25% power is going to be dimmer than one drawing 50% power.
The resistance of a filament bulb is very temperature dependant Driven at half the voltage it will take more than half the current because it has lower resistance. The buck convertor does not "double the current" when it halves the voltage. It doubles the available current. The actual current flow will depend on the impedance of the load among other things.
Julian, The fifth pin on the transformer is there so it can only be placed in a circuit board one way around. It has no electrical connection. Thanks for the videos. :-)
Thats what a grounding pin is for...
+Mark Earth pin. The ground pin is the 0v pin
If you want to crimp that sort of terminal with pretty much any pair of pliers, put it between the handles, all the way up there. Does the job quite nicely, that does...
Guys, just because Julian's converter would have awful ripple and noise doesn't mean that it's not a DC-DC converter...
(Yes I realize the output is not exactly DC but nothing IRL is tbh)
Half way through and in rooting for you, great teaching btw :)
Nice follow up Julian; looks like it behaves like a buck to me; love the videos, please kep them coming.
the light bulb changes load when given different inputs so that was not as conclusive as it looked. You need to use something less reactive as a load, like a low temp coefficient resistor.
I learn a lot from your videos. Wish I had this resource when I was a teen.
Nicely done Julian! Very good demonstration that it is, in fact, actually doing buck conversion. You could of course use the information that you got from the ammeter and the voltmeter to compute the efficiency as power(out) / power(in). You had ~ .144 Amps at 10V, on the input side, and ~.190 Amps at 5V on the output. Since power is voltage * current, the efficiency is (10*.144) / (5*.190), or about 66%. Nice.
Now you can use the same components to build a boost converter
Great stuff. I had sort of wondered if the pwm was doing all the work but i knew that the buck had to be doing at least a tiny bit. I figure they ultra low efficiency your seeing here is due to the inductor. It looks as if that inductor might be better suited for 500khz or more, maybe even into the tens of mhz. You also mentioned it may not actually be a very good square wave which will be interesting to see on the scope for next video. If you can crank up the PWM frequency, or drive the mosfet directly from the sclk on the MCU, That would be really fun to see. Cheeerrioos! :)
Good points well presented Julian. Always enjoy your tutorials, always
I would guess that the lamp gets brighter when the inductor is shorted because the power dissipated in the bulb is V^2/R. With pure PWM (inductor shorted) you get bursts of full voltage, whereas with the inductor in circuit, the voltage is reduced---so you lose out from the V squared term. (The R of the bulb does not change very much.) (I would also be very cautious with current readings in PWM mode.)
Nice update Julian. I wonder if anyone dares to criticise this time :-) I'm still a fan of the lamp, and the reluctance to grab the expensive tools to prove what's going on. So many don't have access to them.
Oh, and I'm guessing the noise you heard from the soldering station was a loss in the step down transformer. Was that all planned? :-)
haters will hate.
Adam Welch challenge accepted: I am still not sure how to pronounce his last name and he talks with a funny accent...only cause Adam dared me.
My biggest serious critique is TAP that bolt out man! I know it's driving you crazy too, I know it is. Also, I have a bunch of cores and magnet wire if you want to wind your own inductors too...I know you did in a couple videos back but didn't have the large toroids, I'll send you a handful, just let me know.
I'm going to have a bit of fun replying to some of these comments.
Great video as always Julian, we would like you to see you doing a Boost converter on your upcoming videos.
Good tutorial. Good approach. I think you made the point quite clear.
The simple fix for this is to add a large cap across the output. That will hold peek voltage and if you are then getting dimming still, then the buck is definitely working.
You could also control it with a 555 astable with pin 5 as the mark space control.
You'll have to use a separate supply for that s using an nch fet there makes it complicated.
I can see you getting a voltage drop over the light bulb. when you pull out the two wires?
Julian, I really like the way you handle the difference of people's understanding...you calmly and methodically work through the circuit to show what really is going on and how it works. Never taking criticism personally (I wish had your patience), you make a wonderful teacher. Thanks again for your video.
I would say, no feedback to complete the regulation but it is definitely a bulk dc-dc.
Capacitor is needed to smoothen the output but with that not in place doesn't mean it is just a PWM.
Please do the oscilloscope test! =)
I'm pretty excited to see the results.
Would it show massive ripples? Small high frequency ones? Or Would it be as clean a battery? =D
Ronell Oropesa it will be clean as battery FINALLY. You should know who is doing it
Ronell Oropesa Because this circuit has no smoothing or regulation components, the DC output is a series of pulses.
Now it would be nice to see what happens when you vary the PWM frequency.
Make a Boost Converter Next?
Bruce Mang Yes Hope Julian will do a Boost converter next good idea 👍👍👍👍
Julian Any chance of doing a Boost converter next please.....by the way I loved the Big word Ratiometric lol ☺👍👍👍👍
I enjoyed this video. It's been decades since my circuits classes, but you remind me of one of my favorite instructors. Have you ever done a "black box" analysis of a circuit? I.e., there's a circuit in a black box and the goal is to figure out/recreate the functionality of the circuit without looking inside.
Hi Julian,
You could just understand that this circuit is a buck converter or not by changing input voltage and you could see the output brightness should stay same.
Wouldn't that be the case of a regulated buck converter?
well done, Jules.
Plz make a video showing basic and advanced tools u use and link to buy
There is a defference betweeen ac and dc there is no ac in this circuit. Ac change polarity between the two wires. Actually what we have is pulsating dc so it's a dc to dc converter. If you put a cap on the output the voltage and current will remain the same, however if you take off the load the voltage will rise as it charge the cap. You should remember it's the pulse width that cause the voltage drop it's still the 10 volts switch, so with no load it will say 10v on the output. But then again Julian say it's not regulated so the circuit is working as it should not the most efficient but it works.
Could just throw a 12 volt led emitter on the load and it'd only light/increase in brightness if there was a voltage boost.
I am looking forward for a follow-up with a scope :D
I think it would be a better demonstration, if you put the diode reverse biased where the inductor is, and the inductor in the place of the diode. We would then be assured that the power supply wasn't lighting the lamp and the power was actually being supplied by the inductor.
hi Julian I hope you don't mind me contacting you but I have query I need a little help with im currently in the process of building an hiland 0-30v power supply that I am fitting into a nice case so I am changing the 2 pots for a nicer range of voltage but I got 2 5k pots instead of 10k pots by mistake what I need to know is what difference would it make to the power supply using 5k instead of 10k pots cheers peter
Is there a more elegant way of driving that mosfet - can you make a DIY oscillating circuit?
Isn't it just a case of the inductor is acting like a resistor as the bulb dims as the link wire is removed, causing input current to drop.
arif anwari No. The resistance of the wire of the inductor will be fairly low, in fact most likely lower than that of some of the connecting wires that he is using.
Julien, i was wondering on these digital controller part of the power supply, there are terminals for VCC, xD, RxD, grnd. Can a bluetooth interface be hooked up, or something else, if not whata it made for?
Julian, in your next video in this series, could you spend a moment or two talking about why it does or does not matter that the 0 volt lines are not tied together in this circuit? Ta.
Craig Harrison In what way are the 0V lines NOT tied together???
Mark 1024MAK I am not really sure, hence the question. My thinking is that the 12v supply coming in from the left is from Julian's Lead-acid battery array, has a 0v line that is independent of the Uno's power supply. There is some sort of voltage being supplied to the gate of the n channel MOSFET on the top left of the main board, but for that signal should be somewhere above the 12 volt supply to turn the MOSFET on, so I assumed that the signal voltage should be referenced to the same 0 volts as the main board, but there does not look to be any kind connection between the 2 zero volt sources. In other electronic projects that require different voltages eg a 5v and 12v supplies, there is usually a single 0v rail that both these voltages are referenced to. I am still unsure so if you or Julian could discuss it ( I would prefer J himself personally as I find his style of explanation very accessible) then I hope to learn a bit more about the finer details of this project. Hope this helps with understanding why I asked the question. Ta
I just realized something. How do I power my buck converter? I need to step down 54 volts (e-moped battery) to 12v max 10 amps. So I am looking arround and sadly many youtubers fallback to the 2576 whicg cannot go high enough and is only 3 amps. I I really want not go the arduino way and you do a great job! But how to power my arduino from that 54 volt battery? Right now the only thing I can think of is to use a lightweight buck converter (I have several XL7015 based 80 volts / 0.8 amps buck converters) but it feels a little silly?
Hello Julian Ilett, greeting from Indonesia!
Currently, I try to build my buck converter, sadly I haven't succeeded in converting down the input voltage. If you don't mind could you please tell me about what kind of or what type of PWM driver that you used in this video?
your help means a lot to me :)
Thank you in advance!
Question for you, Julian... If you take a 240-24V AC-AC transformer and connect its secondary side to the secondary side of a 240-4V AC-AC transformer, how many volts would you get on the primary side of the second transformer, and would you dare touch the leads with your fingers on one hand?
I don't think doing it with fingers from both hands would be a good idea, though...
You would over saturate the core on the second transformer and it would basically become like a short circuit on the first transformer. It might work a little bit but you wouldn'tget the high voltage you were expecting. Sorry.
You are over-complicating the scenario, Zero
Wouldn't you need to include negative feedback in the controller? So the knob would set the voltage target, and the Arduino would increase or lower the PWM duty depending on if the output is above or below the target voltage?
The output voltage will be different depending on the load otherwise.
A bulb is somewhat self-regulating. Higher current, higher temperature, higher resistance. It's not very good regulation at all, but it''s good enough for a simple testing situation such as this.
IF you aim to get a specific voltage. The voltage changing depening on load is kind of irrelevant, as it still a buck converter.
What about feedback with constant voltage output with some sort of voltage divider... Then feed that back into the Arduino as some "feedback" voltage divider type circutry.. regardless if it's pwm or not, ... works either way I'd think. Good video. +1
You are awful tight with that volt meter. Do you have to pay per reading?
I believe 30kHz ripple in current meter will be causing measurement error.
As many have already said "Add a 100uF" capacitor across input AND output output to give you DC with minimum ripple. Then meters will read accurately.
With capacitors added the difference between PWM and BUCK will then be easily seen when shorting inductor!
Two capacitors each side. You're dealing with square waves here, so there can be some really high-frequency components involved. Electrolytic caps have poor ESI, so the usual approach is to use an electrolytic and a lower-value, lower-ESI capacitor in parallel.
Vyl Bird Do you really think adding small capacitors (100uF and a smaller non-electrolytic type) will make any significant difference given that the load is a current hungry filament lamp? The answer is NO.
ESR of 100uF is around 0.3 ohm. Lamp resistance is around 5-10 ohms so 100uF will take over 90% of the ripple current. If current meter monitors lamp current only (not capacitor current) then its current will be mainly DC.
Would you simplify the circuit with a 555 timer chip? (And a cap at the output)
Hmm... makes me wonder how that circuit would behave if that inductor is replaced with a ceramic capacitor similar to the solar PWM circuit that you built a while ago :)
tbbw The lamp may (or may not) light very briefly (depends on the size of the capacitor, a ceramic would be far too low a value, so the lamp would not light at all), but would then go out and stay out. As the capacitor would charge up when the transistor is switched on, but it has no discharge path, so once fully charged, there will be no significant current flow through the lamp.
It would actually let the AC current though so I imagine it would be just like the PWM.
Just tell me please why is the current in the "secondary" side higher now? My guess inductor drives the charged up (remembered) current when the switch opens (knowing the current slowly decreases of course depending on switching frequency and in inductor value) instead of just being zero if the switch opens - so therefore just increasing efficiency??? And now assuming your A-Meter (which looks great ;) does a little bit of averaging (maybe filtering?) the overall measured current is now higher in the "secondary" switching side.?
Please tell me i am somehow right i graduated not so long ago from electronics .. but buck and boost converter well these things i have to and i really want to understand fully & truly.
My way would go as far as to measure the current in the secondary side with an oscilloscope and to see the current when Switch is open as well as closed
It seems that I was right after all, it is a buck converter even without a capacitor across the load
If you modify the original circuit to make a BOOST circuit it will be easy to tell if it's really working.
Take a 1 ohm resistor supplied at 2 amps for 1 second and 0 amps for one second, an average 1 amp. So using averages gives 1 amp times 1 ohm ie 1 watt dissipation. But power is current squared times resistance so it's actually 4 watts for one second and zero for one second ie 2 watts average dissipation. That's one reason why people buy RMS meters.
BogusNotions You need to think more carefully about what you said.
Really, Why would that be?
Why don't you just view the output with your scope to measure the peak and average output voltage, if it's a buck it will be lower, if it's just pwm the peak will be the same as none buck and non pwm.
Are you sure the beeping isn't coming from the Ann Summers bag and not he soldering station?
Hehehehe. yeah, I just noticed that.
The lamp brightness isn't an indicator of the voltage at the load, but of the average power (and thus average voltage and current). But what we want to see is the output voltage being more like a DC value than pulses of 10V and 0V. All your measuring devices in this video will be averaging internally, so we're not seeing the truth. All switch-mode supply experiments *need* an oscilloscope!
Well I enjoyed that, I usually just use recommended circuits from datasheets for buck or boost ICs so it is nice to see you homebrew something yourself. Still, this comes from a self admitting noob.
can you make a dc boost converter video
Very interesting. Thanks for this!
I like how you've gone for the clever approach of looking for current step up to show it's more than just PWM rather than getting the scope out. However I would struggle to put my faith in your current readings bearing in mind the likely very large and high frequency voltage and current ripple. The accuracy of the readings could be affected by that.
You will need to just get the scope out and show some voltage and current waveforms. If you want to prove your claim that it's a DC to DC converter, show a DC output voltage. Of course the simple explanation of a buck converter which is ubiquitous in the hobbyist community (which I don't like because it doesn't account for the current step-up and can't be adapted for boost and buck-boost converters) is that it's a filtered PWM, so then if you take that definition you're really arguing if it has to be an LC filter or if your LR filter counts (R being the lamp and the lamp also being the load).
Of course you could just add an output capacitor and then nobody would argue that it's not really a buck converter. That's all it's missing. (I think you're correct in that regulation isn't mandatory for the definition of a buck converter, just unregulated buck converters are of very limited use).
Add a capacitor to the output. Efficiency will increase dramatically.
Now wait to get attacked by other subscribers, it happened to me already LOL
It will just average current voltage
very interesting video
Anyone know why the n channel mosfet worked as the switch? What is the gate voltage???
Pohan Huang the mosfet is being switched by the Arduino using PWM, presumably the NMOS has a low enough gate threshold voltage that it can be switched by 5V from the Arduino.
And what's the mm of the power connector coming from your solar? 2.5mm? 5.5?
2.1mm inner, 5.5mm outer
What i don't understand is how the bulb gets dimmer, even though it consumes more current. Can someone please explain? I feel like i am missing something...
You're missing the difference between mean current and Root Mean Square current (RMS).
So a phase shift between voltage and current? The power factor changed? Does that happen with DC pulses?
muh1h1 its because that arduino current meter is not an instrument but a toy. On each cycle the current will ramp up steadily if inductor is present but that toy will sample randomly. So the reading you see there is actually not the actual current. Its a playing with kind video so dont try to find justification
muh1h1 The lamp does not consume more current. The energy from the supply is converted from a 10V voltage supply to a lower voltage supply. If the supply to the lamp is 5V, then as energy cannot be destroyed (it can only be converted) less current is drawn from the supply compared to the current to the lamp. When the switching element (transistor) is off, the magnetic field in the inductor reduces, and current flows through the inductor via the diode, that same current goes to the lamp.
Good,hardware explain 👍👍👍
well I didn't say that's not a buck converter. I said the effect is like a pwm. I suggested that you should measure current to show the current gain. And you did but I think you should have put at least minimal effort to filter the output a bit - just any >=100 uF capacitor
Everyone knows that PWM is the most prominent way to switch DC voltages right? Like that's the way you do it, so if all you see if PWM, he's done it correctly...sure you can use a simple voltage divider or a voltage regulator IC but neither of those methods can handle high/ large current. Just because he's powering it with a small adjustable DC load here doesn't mean he can't put 4 batteries at the Drain and do the same thing. This is exactly what you should be doing it so grab an old computer power supply and try it yourself...then you'll have an "Adjustable power supply"
great video
Put a capacitor before the fet and you should have much more current gain
I love these Videos. keep up the good work. K
Put a scope on the load and see what happens with and without the inductor ;)
Now do a video on boost converter!
What about comapring input power vs. output power
at 14:00 you can calculate it to be 1.44W in vs 0.95W out giving you 66% efficiency
+112FaNa Yeah I recently converted my Arduino ammeter into a wattmeter to do just that :)
LOL at your really expensive crimp pliers
Hahaha, you'll never live down the displaced terminal in the top left, will you?
That aside, you mention at 12:45 that the brightness of the lamp is sufficient as an indicator. You'll remember that this only works for instantaneous changes. For anything else, I wouldn't trust your video image further than I could toss you courtesy of the unscryable influence of your current daylight and your camera's exposure control. Cheers!
I'm happy to have been proved wrong it's certainly not the first time. I was worried you had joined the free energy nut job fraternity that make big claims based on no evidence. I begrudgingly admit you may be correct LOL. I would still like to see the scope traces, but more excitingly I would like to see it running closed loop with the lamp staying at the same brightness as you vary the input voltage. I assume what your driving it with has an analog input you could use to modify the PWM. Best regards Chris
..now needs a capacitor across the output....😊
Ann Summers? You dark horse Julian!
maybe the buck converter is for a future PWM controlled vibrator project
Osilocope wave forms pls
These videos come out so far apart these days that I think Julian will be on reduced income this month.
Next time you are screwing terminals in tight hole just add some oil so the wood doesn't clamp(stiction - sticking friction) on the metal.
The lamp is great for visualization, but unfortunately is a non linear load. Would be cool to see just a resistive load next time.
Hi Julian, thanks for this vid!
I'd really like to see you explain the physics of the inductor.
How it is that it 'stores' current/voltage (difference which capacitance).
Some chat about the circularity of the flow, dynamics of the fields effects on itself's coils.
Why it is that voltage/current changes.
Mark T Inductors (all types including transformers) store energy as magnetic fields. A change in the current flow causes a change in the magnetic field. When you switch off or reduce the "input" current flow, the magnetic field reduces, which induces current in the windings.
Around 2min I started scratching my head.. later.. harder.. later.. much harder.. where is the scooope Julian?! :D
FERCSA I am becoming bald due to the same reason
Use that transformer as variable inductor… or get 120/240V at its output...
emmm.... i won't say DC-DC buck is exactly the same as AC-AC step down as its primary and secondary coil are totally electrically isolated from each other and whats actually causes the creation of lower voltage is the magnetic flux cutting the high permeability core in most cases iron core is use which faraday law applies.
DC-DC buck in another hand has no electrical isolation involve where the high "magnetic charge" in the choke release and converts to electrical current at the last direction of flow during 0V.
Reese Me If it helps, mentally exchange the isolating mains transformer for an auto transformer...
Get the scope out! get the scope out! get the scope out!
:-D :-D
You cleared thing up and then threw in a transformer as a strange analogy...
needs capacitors now lol
interisting nice video :D
Sorry but I reserve judgment until I see the scope displayed output.
Lawrence L How do explain the input current being lower than the lamp current then?
Lawrence L it's a Buck converter just a really crappy one but a buck nonetheless.
If you add output capacitor efficiency will improve drastically