Hi Clive. I was the original designer of the Pulsestarter in conjunction with Texas Instruments who were responsible for the original main thyristor power device. The data sheet you reference was the original design which was manufactured over a number of years by a company called Arlen in very large quantities. The original concept was based on the fact that preheating the tube cathodes (proposed by a very clever guy called Mike Lester) would increase the expected life of a flourescent tube. Resultant testing proved the fact so much that some extended life testing we had running was eventually turned off after 1 million successful strikes on, I think from memory, a batch of 58W T5 tubes. The idea was that after the preheat cycle, a number of pulses would be applied to the tube as the small thyristor would turn on but not have enough holding current to stay conducting at first but would eventually latch after a number of cycles.This meant that you were always attempting striking with hot cathodes and, unlike a standard glow starter, you avoided overheating and possible fire issues with a dead tube trying to keep on striking. BTW, love your videos which I only found recently but now watch often.Keep up the good work.....and the gin, which is one of my favourite tipples :-).
Hi Maurice. Am I right in assuming that the TN22 keeps getting retriggered, but driven off by the gate being pulled below the cathode, or is DiodeGoneWide's answer correct? And also, what is the reason for the resistor in series with the timing capacitor? Is it just to provide a bit of ripple to give the transistor, or the P0124 a bit of a nudge on? Another possibility I thought of is that the ripple from it peaks as the current peaks and makes the darlington drive the TN22 off then to get a good discharge from the inductor. Is that true? But that would not explain why they had it when they had a C106D, which is not a GTO, so maybe it helped trigger the P0124, and now unfires the TN22 at maximum current. I'm curious, please write me a reply. Cheers!
The old starters were brilliant - use a couple in series with small coloured lamps - orange and red - and you could create a very realistic bonfire stage effect.Lovely random bi-colour flicker.
Oh dear, if Clive doesn't immediately understand it, it must be deep magic indeed. This makes me feel much better, knowing that I'm not the only one who gets bewildered by seemingly simple circuits.
Once the 47uF capacitor is charged, the transistor turns on and stays on. It steals most of the current from the gate of the thyristor. A low current flows gate-cathode through the thyristor, it is not enough to turn on the thyristor, but it is enough to keep the transistor on. And as the transistor is on, it still eats most of the current, so that there's never enough current for the gate to turn on, but some little current to keep the transistor on.
The SCR gate is shorted to ground when the transistor is on (that's why the transistor is there). How can it get power from the SCR to keep the transistor on if the gate is shorted? How can the cathode have any voltage on it?
The transistor is not fully saturated. Its voltage drop is enough to allow tiny current flowing through the gate-cathode junction and then through the base-emitter junction. A negative feedback keeps this current stable.
Which I believe it raises the question on why the SCR even turns ON the 1st time ? In other words, even on the 1st time, as the 50V 1uF cap voltage increases, the gate-cathode current increases, raising the base-emitter voltage of the "NPN" , which could eventually start stealing enough current to prevent the 1uF cap voltage to further increase, stopping the SCR of ever turning ON. My guess is that the 47uF comes to the rescue here, when you 1st turn ON the light because it is fully discharged. The times constants are fine tuned such that the SCR turns ON way before the "NPN" is even close to go ON. But once the SCR triggers now there is plenty of current to complete charging the 47uF at the fastest pace possible. On another topic, nowhere I have seen that a SCR, once ON, can be turned OFF by playing with the gate terminal. Usually they just talk about the hold current. Having said that I am convinced it is the "NPN" that turns OFF the SCR, though I am not sure how.
Yes, DiodeGoneWild is right. There only has to flow a few micro-amps through the gate into the darlington's base to keep it on, which is not enough the turn on the thyristor.
The company I worked for years ago illuminated their stores with skylights and fluorescent lights. They got swindled into light sensing controllers that would shut the lights off when the sun was bright enough and would turn the lights on when sun went behind clouds. Well on a cloudy day, the lights can be turning on and off every couple minutes. Needless to say they were going through bulbs/starter/ballasts like crazy...and to top it off, the energy bill wasn't really any cheaper. If you live in the US, you can still see these at Home Depots, some grocery stores, maybe even some Walmarts...and you'll see half the tubes out.
I've watched many, many RUclips videos all claiming to explain how the fluorescent starter works. This is the only one that explains it fully, clearly and correctly. I especially like the bit about not connecting a starter directly to the mains. Yes, I have done this too! And yes! A very large pop it did make too! Thanks Clive. This video made my day.
I'm still not fully understanding why. Is it because they're only expecting the full mains voltage for a fraction of a second? But then what if the tube fails to strike? What stops the circuitry from constantly attempting to strike it, and why, given that an unlit tube doesn't drop the voltage, does the starter not simply explode?
I haven't seen one of those for 20 years or more. I didn't realize they are still used elsewhere. I'm frequently amazed at how different things are here vs over there. I used to replace lots of ballasts, both 120 V and 277 V depending on which building I'm at, but now whenever a ballast goes out it's cheaper to just rip it all out and rewire the fixture with line voltage going directly to the bulbs, then pop in a couple LED tubes. Hopefully by the time those need replaced I'll be retired.
I have an RS branded electronic starter, had it for years, and it only stopped being used when I replaced the fluorescent tube in the kitchen with an LED tube, never seemed to fail unlike the traditional starters... :) And as for traditional starters, I recall seeing them used in someone's halloween project to create a "faulty wiring" effect, which you recreated in this video, quite impressive and a simple circuit too... :)
Thank you, Clive - I've always wondered how those starters worked, and you also settled it for me as to what makes that really annoying, and sometimes quite loud 'Klak-klak' noise. My local Co-Op had a particularly irritating one the other week. Cheers.
There are floresent light fixtures rated for colder temps. Here in Northern Mi,we have to make sure all the fixtures are rated for cold temps. I remember having the older ones in our barn and when you turned them on in minus 20 degrees,they would only flicker off and on. It was way too cold for the preheater to get the light to florescent. We always had to make sure we had regular clamp type lights in the work areas. Problem being it was so damn cold your fingers would freeze to the tools when working on tractors,snowmobiles or our trucks. My dad put block heaters in all of our vehicles. If you forgot to plug in the vehicle,you had to put a clamp light under the hood for an hour,usually down by the starter. Before the block heater it was a 100 watt light bulb in a work light with a wool blanket over the engine. I remember frost would build up in the carburetor, then it would suck it in to the intake. You had to use ether to get the damn thing started. Especially the ford tractor.
In my early days I just loved florescent lights but hatted the turn on flashing. One day I was looking through the RS catalogue (as one did) and noticed the electronic starters. I replaced ever one I had and just loved them. It only ever struck once after about 2/3 seconds, noiseless and zero flicker. I still have a few in my bits box today. No idea why I keep them as I am 100% LED these days.
The old starters were abysmal! I once lived 50 metres from a 'corner shop' [Spar]. One morning I go on the air on 20m with my ham station and there are ENORMOUS clicks about every 0.7s across (as it turns out) every band. I scratched my head for a few hours (at work) and finally concluded it must be a light. Sony ICF7600D in hand I find a huge signal when outside the shop. Look in and presto! One of the tubes is flickering on and off. I went in and pointed out what was happening and luckily they changed it (the tube) right away [it helped that it even showed on TVs and I pointed out I would tell the whole neighbourhood that their TVs were being 'attacked' by the local shop!!!!]. Luckily, after a couple of occurances of this they fitted electronic starters and the problem more or less never re-occurred.
Back in the day I was using starters for making Christmas lights blink. You had to try quite a few starters until you got the desired effect and as the starter ages the frequency also change. It was very exciting. :D
Would the voltage at the zener diode be lower because the fluorescent tube is now lit and therefore, no voltage would charge the capacitor to turn the thyristor on again (and thus, it would not try again)?
The Pulsestarter doesn't simply open when it's finished preheating - it opens and closes very rapidly over a half-second period, or until one of the openings causes the lamp to start. Also, the diode D1 (at least in my unit) is a peculiar one, with a ~3V forward voltage. This might help with some of your confusion with the circuit.
I was finally able to see what the name of that switch assembly was, and then you said the name of it. I have been wondering for some time what it was but never heard you put a name to it in the videos I have watched. Thank you Clive.
Finally understood the reason for the "high holding current"... When the drive to the thyristor is removed, it WON'T wait for the zero crossing, but will cease conducting while there is still current to provide a kick.
Great topic, these fluo lamps. They were a big mystery to me when I was a little kid and no one around to explain to me how they work. Unlike the so intuitive incandescent light bulbs😊
11:15 Technically speaking there's a different terminology used depending on application. Choke - to block RF and Ballast - to limit AC current, also typically ballast would be much bigger and have higher inductance.
I used to like charging those little caps up with 500 volts (with an insulation tester) and throwing them to people while saying 'here catch'. This was back in the 80's when you were still allowed to do bad things to people at work.
Rabbi Zyklon Brausebadstein when I first heard about that I was shocked. Sorry I had to, I used to heard those stories. Unfortunately most people are already cautious when I throw things at them.
Or asking a fellow student to hold a granate and walk away with the pin. And then after 20 times you had private lessons. Yes we had a tough school in Aghanistan
In my electronics class, everyone just melted blobs of solder and catapulted them from the irons. We had no way of charging any capacitors because our teacher knew we would try that lol.
So THATS what those are! i saw a bunch scattered in the bed of a truck from this pawn shop and i couldnt figure out what they were. Thanks for this video (literally within a week of seeing them for the first time lol)
From what I gather the resistor below the transistor's base forms the bottom of a voltage divider which must account for why it works. I am more shocked to see an actual circuit with discrete components in that starter case than anything. All the ones I have torn open never had anything that complex in them. I think I even have an old one down the basement that has a removable starter that is resettable. I got that FL unit from a city worker where they used to keep the snowplow trucks -- apparently it is extra good at staying lit in our frigid sub zero temps. Good vid, Clive.
Believe it or not my _other_ boss had a hand in this one. I say a hand, the design was done but needed tweaking. We got involved because they were being produced locally at the time by BG Electrical. Now my boss is very smart, and he struggled with it. It's a good demonstration of a design that's almost too clever for its own good. Boss is on holiday right now and the job precedes electronic records so I don't know how much we have but I'll see what I can find.
Hi, Bigclive. Thanks for making this video. I remember making a request for it ages ago.. Shortly after your 'sudden science - driving fluorescents' video was released a year or two ago. Have always wanted to know how these work. Time to grab a beer, sit back, and be enlightened. Keep up the brilliant videos. You're my favorite subscription :D
I've seen these starters in my childhood in the 80s when one broke. They all looked like the white plastic housings, but they did blink the lamps several times. Also after they were replaced, I haven't seen fluorescent tubes go on without prior blinking until the end of the 90s or even early 2000s.
The electronic fluorescent starter could work well as an April fool's - Wire it in series to a table light (assuming incandescent) and set up a candid camera. When the victim switches on the light, it goes out, leading them to replacing the "blown" bulb and of course the same with each spare bulb they try. I have wondered how they claim to increase tube life and indeed the longer warm-up period and single strike explains a lot. Another clear benefit is that the cutting off also saves electricity on failed tubes. With a standard starter, the ballast is effectively shorted with endless start attempts, consuming more power than with a working fluorescent tube.
Seán Byrne They are very effective at increasing tube life because of the mandatory preheat. Where circular fluorescent tubes are used in ceiling lamps, they do not have guard rings on the cathodes, so the tube ends blacken very quickly. But with the electronic starter they hardly blacken at all. On many tubes started by these, the phosphors in the tube wear out before the cathodes!
2:21 If the starter is a part of the circuit as drawn, why is it then possible to remove the starter, after the tube is lit ? That would make it an open circuit and no current would be able to flow ?
@@bigclivedotcom Yes but as you draw the starter in series, removing the starter should break the circuit, would it not ? This is what i dont understand. There is no path for the current to flow between the live and neutral if there is no connection in the starter.
@@bigclivedotcom Aah, i think i see it now. It's because i thought that there should be a closed circuit, thru the 2 coils inside the flourecent tube. The circuit when the tube is lit, is actually going from the top pin of one side, through the tube to the other. Sorry man, i just had to understand it :) Really love your videos, keep up the good work.
Hello Clive, I enjoy the content of your videos. There is a large AC ripple content appearing on the bridge output , this being unsmoothed ., the positive going pulses appear at the transistor base via the 47 mfd and 56k, pumping up to Vbe, thus keeping the transistor on after it initially triggers. It cannot turn on prior to the initial trigger because the 47mfd/56k time constant is longer than the 15k/1mfd. Once the tube fires, there is no voltage available through the zener, the SCR remains off. If the tube doesnt fire, the ripple voltage continuously removes gate voltage via the transistor shorting the 1 mfd until the power is cycled. Its a bit of a trick circuit to be sure......
Ah thank you! I think I get it now. I watched the video and read the comments explaining it further and I didn’t honestly understand it until I read your comment. I felt like I was the only person that didn’t get it still after reading the further explanations. I can’t believe I am the first person to give you a thumbs up 👍
If the 24k resistor was lower value then that would steal the current from flowing into the base and cause the transistor to turn off, thus allow multiple attempts at starting the tube?
Well this brings back memories of the 70 ish I was about 14 and was amazed to discover that putting a starter and a light bulb in series, the bulb would flash. So I started building disco lights for friends. However my parents soon put a stop on my electrical explotes, not on safety grounds but because my testing was messing up their tv watching downstairs with rf interference.
wow Mr Clive, my fount of knowledge on the dark art of electronics, flummoxed by the recipe for this spell, tubus onestrikus. Broken Britain, I tell you.
I've been mulling it over in my mind and I'd guess that even when a lamp has failed to strike the thyristor will fire briefly to keep the capacitor topped up.
From the TN22 data sheet. It says on page 8 " If the lamp is not ignited after several attempts, the starter circuit can automatically stop the ignition sequence." How does this work? I see how the sequence will start again after a failed attempt. Just not how it will automatically stop the process after several failed attempts.
How is the darlington getting switched on if it has only one diode drop on the base? Is ist because of the diode drop being rather high due to the high current trough the thyristor?
Great video. What do you call the mains connecter that you connected the light up to. I've been trying to find them, but don't know what they are called. Anyone know where I can get one?
I think the zener diode prevents the circuit from retriggering. As you said, the tube voltage when it is ON isn't 220V. Or did I get that wrong? So, the zener voltage is high enough to prevent gate current on the tiristor when the lamp is already ON. This one should retrigger I think.
i remember cold start and rapid start starters. also for the army we had some florescent lights that you could turn on a small tungsten light to warm it up. Physically warm up the florescent tube.
The early dimmable fluorescent lights had a tungsten lamp to provide continuous current to the cathode heaters and make them dim more stably over a wider range.
6:58 Hehe. Memories. I when I was 12 I think, I hooked a little bit bigger neon glow lamp up to the mains without resistor. Man. I got scared. Little glass shards all ober the workbench and floor. I should have known what I was doing. Thank you for sharing your knowledge and good night from Germany.
Here is how I think this circuit works. The gate-cathode junction of the thyristor conducts just like a diode and the thyristor will not fire if the gate current is low. When the transistor base voltage drops by discharging the capacitor, the transistor turns off and the gate voltage rises, recharging the capacitor. The transistor keeps the gate voltage below the threshold. The gate current (capacitor charging + transitor base + diode) must be kept below the threshold to keep the thyristor off (for lower consumption). In the case of the gate current of the thyristor is above the threshold it will conduct from anode to cathode and will recharge the capacitor the same way the gate-cathode junction would.
I think the reason it only tries once is the 47 uF cap on the transistor via the resistor, the 82 and 24k providing a discharge path when power is turned off. Once that cap charges the current flows through the transistor instead and not providing a gate cathode drop high enough to trigger the SCR and perhaps leakage from Collector base when the transistor is on is enough to keep the cap charged.
As I see it: The fluorescent lamp should get lit by the coil spike after the thyristor gets shut off. After that the voltage over the circuit is low enough to prevent a restart, the zener doesn't provide current. If the lamp shouldn't start the voltage rises high enough to conduct the zener again and the cycle starts over once more. The R2, R3 and R4 should be dimensioned such that the darlington doesn't conduct anymore at a restart. Now I have a question: the darlington input needs 2x 0.65 Volts, is the series D in the main circuit a version with a higher voltage drop?
Used to make disco lights using a starter on each one off theses RED GREEN BLUE spotlights and there also great for flashing Christmas lights did you know if you alter the value of the capacitor across the flasher you get different flash rates
The Darlington has 2 Vbe drops on the base, so there is a question as to how the Darlington turns on in the first place, given that it is driven by the forward bias voltage across the diode in series with the thyristor. The Vf of the diode should be less than or very close to the base on voltage of the Darlington. so is the series diode a sense and the diagram has it the wrong way round or is it a diode with a high Vf? The high Darlington gain means it's base current will be very low, so the charge on the base capacitor will be able to maintain the clamp on condition for some time, particularly if the capacitor charge is not able to flow back through the diode in series with the thyristor. This again point to a high Vf for this diode or more likely that it is a reversed biased Zener diode with a Vz greater than the two standard Vbe drops of the Darlington. It is like therefore that thyristor triggers more than once, but with a very long period between trigger points. As there is not any hysteresis in the Darlington circuit, it is likely that after the initial triggering that charges the timing capacitor, subsequent triggering a will be of a very short duration ( maybe just a mains half cycle), sufficient to recharge the capacitor and reactivate the clamp. Knowing the excess voltage across the charged capacitor and the Darlington base current it should be possible to calculate the trigger period. The resistors connected across the capacitor likely control the trigger period so that the circuit will trigger reliable each time the mains is turned on. In the case of the recommended circuit that uses a second thyristor rather than a Darlington as the clamp, the clamp thyristor will fire just once as C1 will maintain the clamp thyristor hold current through the zero voltage of the mains cycle.
bigclive, i suspect the transistor shorts out the 1uf capacitor thus drags the operating voltage down for the power supply and then is held low. hence the thyristor cannot be triggered again regardless of the power supply coming into the starter
Are there different rated starters for specific wattage tubes? We have a 2ft tube that blinks like mad when first turned on. I replaced the tube and the starter but it still behaves the same.
Yes, they all have the range of wattage of the lamp they can work with. Compact tube florescent have a much lower range than the larger tubes but that should be printed on them. As here: static.bltdirect.com/cache/images/Fluorescent-Tube-Starter-4-65-Watt-1-700x625.jpg
Oliver Dawson yes s10 starters for say 4f and 5f tubes then you have s2 starters for fittings with (2x18w) 2x2f tubes not sure how it is in the US. Hope this helps from an aussie sparky
Back in the 70's (in Iraq), I made a poor man's Sound-To-Light unit using starters & different coloured bulbs... It randomly flashed those on & off and had no connection to the music or sound, but it was fun, and I lived to tell the tale...
If I am understanding correctly, this is basically an automatic version of the manual red "start" button on some desk fluorescent lights? I do remember my father's old shop having the lights flicker when you turn on the switch. Good old magnetic ballasts. I remember seeing several cards of starters in a local home center about a month ago.
Basically, yes, but I would never have thought of the term "automatic" for those glow light starters that are still quite commonly used over here. It wasn't until copper became so expensive that magentic ballasts started fall out of favour and were replaced with electronic ones in new fixtures. But there are still loads of magnetic ballasts around.
I'm guessing the the leakage current through the thyristor allows a small amount to current to flow after it's attempted to start the tube. Since the transistor is a darlington an extremely small amount of base current would allow the collector to stay below the threshold voltage of the thyristor and never letting the trigger current flow into the gate.
I had heard quite some time ago that flourescent tubes had an expected lifetime that was based on the number of times you started it up, and it was never quite clear to me why this should be, until you explained it in this video. I'm guessing that this is the reason that a lot of commercial properties like large office buildings are left illuminated all night long in places like New York City, as opposed to turning the lights off. Their cost for the electricity would have been less than having to replace the bulbs more often, I guess.
Here's a great one for ya. My aunt brought by a pool pump for me to fix. She said it got wet and wouldn't turn back on.I just told her it's too complicated to fix. People don't get safety mechanisms.
One of the joys of RUclips is that there are a lot of really good educational channels which are not only enjoyable to watch, but are free too. It's what the Internet is for.
When the transistors conducts, it is discharging the (charged) 1 uF capacitor. This might cause a short peak with a high current. Will the transistor survive this? (No current limiting resistor!)
i have an old late 80's salad fridge from a resturant i work from and it uses those things all 3 tubes. nice to know more about them as i always wondered one of them is original glass tube one in a tin shell but other ones were replaced by me when unit was still functioning years later before retired it and taken it home. i do like the clicking though it just sounds neat specially when tube flickers alot sure it ruins life of it but i dont know just sound and seeing it do that is fun
You've got the way a thyristor is triggered the wrong way round - the Darlington shunts the gate voltage here, stopping the the thyristor triggering. Given long enough the cap on the base will discharge and the starter will have another go at striking the tube - there's a clue in R4 labelled 'Reset control' on the datasheet cct. And now I've looked at the full datasheet that is what happens. However there's there's a problem with the ccts as shown if I'm thinking straight. If the diode (D1) in series with the thyristor is a normal one its forward voltage won't be enough to turn on a Darlington and I'd not like to bet it would reliably turn on a thyristor either. Edit: When hand-drawing a Darlington I just put two arrows on the emitter.
Only thing i can think of is a slight leakage that keeps the cap alive Many years ago i was asked to put a warning light on a freezer room door (room was in a cold room), so if the door wasn't closed properly they would know from the corridor, i installed a sealed industrial limit switch in the door, and fed it out to a red bulkhead fitting, to make it more obvious i wanted to use a flasher unit, but then i thought about using a starter, just the normal mechanical (glow type), but it worked well for many years, and because of the random flashing it was much more annoying and obvious.
In the US we have old desk lamps that use Manual starters. The Japanese versions of them are even simpler. I will describe the Japanese makes here, but the American models simply have a latch in the off button added that is unlatched when the start button is pressed. When the desk lamp is plugged into the power outlet the line voltage is present across the lamp and ballast, but the lamp is not lit since a starting cycle has not occurred (note American units the off switch is usually still latched open). When the on button is pressed the start contacts are closed (dual tube units have two sets of contacts here). The on button is held in until the ends of the tube glow and then is released. If the tube doesn't start (either due to dodgy on button or not being held down long enough this cycle can be repeated. When the light is on the tube continues to conduct until the power is interrupted. When the power is interrupted (ether externally, by someone removing a tube, or by the off button for a few seconds) the lamps cool down enough that they will no longer conduct. The circuit in the lamps is rather simple. The off button is a normally closed momentary (latched in the American versions) pushbutton and is in series with the entire circuit. The on button contains a set of contacts for each tube and these contacts are placed where the starter is in the circuit. What's the big deal between latched and unlatched off buttons. The unlatched off button only breaks the potential from the circuit when held down. The tube can still be induced into a dim glowing state or started by external means (static discharge, discharge from a piezo ignitor, nearby lightning strike which is more common on the 14 inch tubes, CRT degaussing within a few inches, etc). The latched version keeps the normally closed switch open until the on button is pressed. Now these designs are not common outside of 100 to 127 volt countries as the tubes must be in series to prevent instant starting with the OCV of the mains in 220 to 240 volt countries. In these countries a standard automatic switchstart circuit is used.
And for what its worth some of the cheaper ballasts have or had that same circuit built into them from what Ive seen. Obviously no longer removable, so if it takes a dump the whole ballast was trash. And yeah lol remember those back in my school on some of the desks since it was a historical site from the mid 1800's. Had to push that SOB button for a while to get light sometimes.
any help off any1 plz.....i hav a 18v AC input and get a 23v dc zap from a 40v 2200uf capacitor is there anyway i can get a bigger zap from this...would a darlington transistor setup help or is there not enough info here to help and im just being a noob....thx for ur time if u read this
Once the Darlington pair transistor fires the collapsing choke field produces a Back EMF discharge that is enough for the fluoro to conduct resulting in the voltage drop across the fluoro is low enough that the Zener does not conduct and cause a re-trigger the heater element circuit. Once the flouro arc is struck there are enough charged particles in the tube for the reverse cycle to reignite the arc.
Looks like a better design than the ones i bought some years ago. First one i got worked fine, so i bought another ten or so. All of which failed within half a year, burning out some almost-new tubes and one even catching fire from a cold solder joint arcing. These had a relay inside and used a single diode to effectively saturate the ballast core with DC current to allow for a larger preheating current (which burns out the tubes and causes a really loud buzzing noise while starting), as for voltage detection they used a varistor (which is not intended for anything other than surge absorption and did burn out). I didnt bother to reverse engineer further, only replacing all the fixtures with electronic ballasts that finally work properly.
Damn dude, I just bought 6 of them today for about 50 cents each, now I'm carefully considering again for the application, thanks a lot for your experiment , really appreciated.
I don't know much about circuitry but I would assume the Darlington transistor is supposed to turn on and off, and then the track with the 1uF capacitor is just where the current goes.
I'm not understanding how those little bulb starts (with the bimetallic strip) work. How does current flow through them (to heat up the strip) before there's a path across them? I know it could arc across, but if that were possible how would the circuit ever open? Also, why do the strips cool down once they make contact (and current is flowing through them)?
@@bigclivedotcom Thank you. So that causes the neon to heat up which bends the strip, right? I was thinking the current flowing through the strip is what makes it heat up and couldn't figure why it could cool once it completed the circuit.
I don't think the diode that is in series with the main thyristor is a zener. The band on it is to the negative rail. If it were being used as a zener it would be the other way round with the band to the thyristor cathode. It could simply be that this diode's forward voltage is high enough when the heaters are on that it will exceed the voltage required to bias the darlington on (after the time delay) and reverse bias the main thyristor, turning it off even thought it still has a voltage across it's anode-cathode. If the tube doesn't strike at this point, I can't see how the starter is going to latch off. The 47uF timing capacitor is going to discharge via the diode (without the heater current it's forward voltage will be lower than that needed to bias the darlington on) and the "reset" resistor. I suspect it just keeps switching on and off, giving the tube further chances to strike. It would be interesting to watch what happens on a scope with a broken tube - after having taken precautions as a scope's probes are usually referenced to earth (and therefore the neutral in .uk).
How does the darlington transistor turn on in the first place ? Its only got one diode drop to supply its 2 x base-emitter diodes and this diode drop is even voltage divided by the 82K-56K resistor divider. IMHO the diode ist not a diode. It must be a zenerdiode to make the circuit work. Something like a 6.8V zenerdiode, as the 47µF must have a charge to keep the darlington on long enough to discharge the 1µF capacitor and sink away this 1µF repeated charging current.
My guess is that you got a mis-read on the darlington transistor, and it actually is an SCR. Try checking the part number on it again. Otherwise, excellent video and great explanation. Thanks!
It's obviosly that the 47uF capacitor that charges a few seconds after the thyristor is triggered then the darlington transistor will shunt the thyristor's gate, since the transistor is a darlington it uses very little current so the capacitor should discharge slowly, I suspect that after the capacitor is depleted it should retrigger the thyristor again. I hope i got it right. Cheers :)
ciprianwiner yes that's right the Darlington could be held off from retriggering the thyristor by a tiny current even putting your finger on the open Base would hold it off so i guess it would take weeks for the capacitor to lose every last nA. ....
I don't see how that would work. The 47µF cap through a 56K resistor has an RC time constant of only 2.6 seconds - and it was only charged to about 0.7V to begin with. For that matter, this MPSA14 darlington has a Vbe of 2V, how does it ever conduct in the first place with the base shunted by the diode to 0.7V? Very odd indeed.
That had me puzzled too but it was the only explaination i got, maybe the diode is not a regular diode? or Clive had it draw incorrectly, maybe Clive could check the forward drop across that diode? Who knows, maybe it's even an actual zener diode and he didn't check it. Cheers :)
Once the fluorescent has fired there is going to be no voltage at the transistor collector that's why that 170v zener is there? Therefore there is no voltage at the gate of the SCR. The transistor is there to take the gate away if tube fails to strike within a certain time, it should reset itself? (Edit) the original circuit using the scr to control the gate would need a power cycle to reset.
The MPSA14 is a germanium transistor with junction voltage of 0.15 to 0.2v. Once the tube starts the voltage across the tube is square (AC peaks clamped at about 100v) & the zener does not conduct, therefore no further conduction of main thyristor. But if by any chance tube does not strike then re-striking does happen. In Old tubes the clamped voltage is beyond 140v. Tubes with still higher clamp voltage has danger of bursting.
Hi. Could you please reverse engineer a crt circuit (tv or monitor) from mains input to flyback I've been trying to figure out how they work, they seems to drive the flyback HV output so much more efficient than royer or zvs circuits , which always needs massive heatsinks, and still blows the transistors or mosfets on regular basis
The flyback circuitry in traditional CRT displays is very evolved and fine tuned for reliability. The circuits used in it are generally mass produced for the task as are the transformers.
It's a simple capacitive pull down switch that's being used as a timer in this instance. Once the capacitor get's enough charge it's no longer pulling the base/gate pin to it's active voltage or vice versa. Think of the dual LED flasher circuit and how it uses transistors and capacitors to switch back and fourth. This works on essentially half that circuit. Since it has nothing to reset it back the other way, it just stays off.
I'm baffled how the transistor gets turned on, since a darlington has 2x Vbe, and the drive to it is fed by a single diode drop - unless that is not an ordinary diode! The "R4" is defined as the reset, I'm guessing it's meant to shunt the leakage to lower the voltage to the point where the switch off SCR / transistor unlatches. I guess the value is too high, with a lower resistor there, it may retrigger.
Just read about another system, the half a second "fast starter", though it sounds somewhat abusive of the system. users.tpg.com.au/pschamb/light.html Described as using "DC heating" and producing a characteristic buzz and magnetic disturbance, I instantly figured out the trick - while there would be a 50% disadvantage in only using half wave control, more power would reach the heaters as the ballast would present only resistance. The other half cycle could be used to continuously detect tube firing. It would be a rather brutal system though, and I can't see it being good for the life of tube or ballast
I don't think I've seen one done before but what would make a great reverse engineering item and interesting to see the explanation on how they work would be a HF electronic ballast for fluorescent tubes if you might consider it Clive cheers Sean
Clive any possibility of showing the circuitry of flourescent emergency lights which incorporates an inverter and batteries along with the ballast. 🍻 cheers.
I have never ever had an electronic lighter failing to light the tubes. They work like, Amazingly good! And they last for decays! My oldest one are like 20 years old, or more!
So, the tiny amount of current flowing through the "off" thyristor (which annoys you if you have a sensitive led which tries to start on it after loading its caps) keeps the transistor active enough to prevent the thyristor from starting... interesting use of something i always viewed as a bad/negative aspect of Thyristors. ( i always hated that you cant really switch off a thyristor dimmer without another mechanical switch to really cut off the leakage current)
The high holding current is to allow for a decent voltage pulse to be generated by the choke. If it had a holding current of, say, 1mA it would open in the moment wehen the choke would carry only 1mA and thus had no stored energy left to strike the tube. (Opposite reason of why you switch off huge tranformers right at the zero crossing of the current.)
Nice video! I like a lot reverse engineering and I am trying to find the transmittion protocol between a generic parking sensor module for a car from China and his receiver.The communication is made through 3 wire,Ibelive that is serial communication but I don't have an oscilloscope to identify the sequence.I tried with a CH340 usb to serial converter but I cannot identify the baud rate.The module is from China is around 12$. Please help me if you can.Thank you.
Hey I'm in college right now finishing my developmental classes. When I'm done I wanted to get Into repairing electronics and stuff. What would that profession be named? Also how could I start learning now?
Hi Clive. I was the original designer of the Pulsestarter in conjunction with Texas Instruments who were responsible for the original main thyristor power device. The data sheet you reference was the original design which was manufactured over a number of years by a company called Arlen in very large quantities. The original concept was based on the fact that preheating the tube cathodes (proposed by a very clever guy called Mike Lester) would increase the expected life of a flourescent tube. Resultant testing proved the fact so much that some extended life testing we had running was eventually turned off after 1 million successful strikes on, I think from memory, a batch of 58W T5 tubes. The idea was that after the preheat cycle, a number of pulses would be applied to the tube as the small thyristor would turn on but not have enough holding current to stay conducting at first but would eventually latch after a number of cycles.This meant that you were always attempting striking with hot cathodes and, unlike a standard glow starter, you avoided overheating and possible fire issues with a dead tube trying to keep on striking.
BTW, love your videos which I only found recently but now watch often.Keep up the good work.....and the gin, which is one of my favourite tipples :-).
Good job. I remember the Arlen brand when they first appeared. Did they feature on Tomorrow's World?
Nice. Ty for your input Maurice.
Hi Maurice. Am I right in assuming that the TN22 keeps getting retriggered, but driven off by the gate being pulled below the cathode, or is DiodeGoneWide's answer correct? And also, what is the reason for the resistor in series with the timing capacitor? Is it just to provide a bit of ripple to give the transistor, or the P0124 a bit of a nudge on? Another possibility I thought of is that the ripple from it peaks as the current peaks and makes the darlington drive the TN22 off then to get a good discharge from the inductor. Is that true? But that would not explain why they had it when they had a C106D, which is not a GTO, so maybe it helped trigger the P0124, and now unfires the TN22 at maximum current. I'm curious, please write me a reply. Cheers!
I always thought that the General Electric research labs was responsible for the development of the SCR. Ron W4BIN
@@pemac8856Hi,
DiodeGoneWild has done another video on fluorescent lamp starters: ruclips.net/video/L0_nJAWty1M/видео.html
The old starters were brilliant - use a couple in series with small coloured lamps - orange and red - and you could create a very realistic bonfire stage effect.Lovely random bi-colour flicker.
oh thats very cool
Oh dear, if Clive doesn't immediately understand it, it must be deep magic indeed.
This makes me feel much better, knowing that I'm not the only one who gets bewildered by seemingly simple circuits.
You Scotts speak funny... A milliamp is pronounced as written.. Milli amp... Not millamp... 😉
+Michael De Angel - Buddy, what in the world are you babbling about?
Brad Gefroh Maybe he responded to the wrong comment
+That Guy - Haha, I think he meant to reply to the video in general, but replied to ME by mistake.
Brad Gefroh That's also a possibility
Once the 47uF capacitor is charged, the transistor turns on and stays on. It steals most of the current from the gate of the thyristor. A low current flows gate-cathode through the thyristor, it is not enough to turn on the thyristor, but it is enough to keep the transistor on. And as the transistor is on, it still eats most of the current, so that there's never enough current for the gate to turn on, but some little current to keep the transistor on.
and of course the gate-cathode junction of the thyristor acts as a diode in forward direction.
The SCR gate is shorted to ground when the transistor is on (that's why the transistor is there). How can it get power from the SCR to keep the transistor on if the gate is shorted? How can the cathode have any voltage on it?
The transistor is not fully saturated. Its voltage drop is enough to allow tiny current flowing through the gate-cathode junction and then through the base-emitter junction. A negative feedback keeps this current stable.
Which I believe it raises the question on why the SCR even turns ON the 1st time ?
In other words, even on the 1st time, as the 50V 1uF cap voltage increases, the gate-cathode current increases, raising the base-emitter voltage of the "NPN" , which could eventually start stealing enough current to prevent the 1uF cap voltage to further increase, stopping the SCR of ever turning ON.
My guess is that the 47uF comes to the rescue here, when you 1st turn ON the light because it is fully discharged. The times constants are fine tuned such that the SCR turns ON way before the "NPN" is even close to go ON. But once the SCR triggers now there is plenty of current to complete charging the 47uF at the fastest pace possible.
On another topic, nowhere I have seen that a SCR, once ON, can be turned OFF by playing with the gate terminal. Usually they just talk about the hold current.
Having said that I am convinced it is the "NPN" that turns OFF the SCR, though I am not sure how.
Yes, DiodeGoneWild is right.
There only has to flow a few micro-amps through the gate into the darlington's base to keep it on, which is not enough the turn on the thyristor.
The company I worked for years ago illuminated their stores with skylights and fluorescent lights. They got swindled into light sensing controllers that would shut the lights off when the sun was bright enough and would turn the lights on when sun went behind clouds. Well on a cloudy day, the lights can be turning on and off every couple minutes. Needless to say they were going through bulbs/starter/ballasts like crazy...and to top it off, the energy bill wasn't really any cheaper. If you live in the US, you can still see these at Home Depots, some grocery stores, maybe even some Walmarts...and you'll see half the tubes out.
I've watched many, many RUclips videos all claiming to explain how the fluorescent starter works.
This is the only one that explains it fully, clearly and correctly. I especially like the bit about not connecting a starter directly to the mains. Yes, I have done this too! And yes! A very large pop it did make too!
Thanks Clive. This video made my day.
I'm still not fully understanding why. Is it because they're only expecting the full mains voltage for a fraction of a second? But then what if the tube fails to strike? What stops the circuitry from constantly attempting to strike it, and why, given that an unlit tube doesn't drop the voltage, does the starter not simply explode?
I haven't seen one of those for 20 years or more. I didn't realize they are still used elsewhere. I'm frequently amazed at how different things are here vs over there.
I used to replace lots of ballasts, both 120 V and 277 V depending on which building I'm at, but now whenever a ballast goes out it's cheaper to just rip it all out and rewire the fixture with line voltage going directly to the bulbs, then pop in a couple LED tubes. Hopefully by the time those need replaced I'll be retired.
I hope you add a sticker to warn against installing a regular florescent, or someone could have a nasty surprise.
Oh yeah! Every time I buy the bulbs they give me a stack of warning stickers and I definitely put them in each fixture I convert.
I think they're mostly legacy installations these days or fixtures that refuse to die in kitchens and garages.
I have an RS branded electronic starter, had it for years, and it only stopped being used when I replaced the fluorescent tube in the kitchen with an LED tube, never seemed to fail unlike the traditional starters... :)
And as for traditional starters, I recall seeing them used in someone's halloween project to create a "faulty wiring" effect, which you recreated in this video, quite impressive and a simple circuit too... :)
Thank you, Clive - I've always wondered how those starters worked, and you also settled it for me as to what makes that really annoying, and sometimes quite loud 'Klak-klak' noise. My local Co-Op had a particularly irritating one the other week. Cheers.
There are floresent light fixtures rated for colder temps. Here in Northern Mi,we have to make sure all the fixtures are rated for cold temps. I remember having the older ones in our barn and when you turned them on in minus 20 degrees,they would only flicker off and on. It was way too cold for the preheater to get the light to florescent. We always had to make sure we had regular clamp type lights in the work areas. Problem being it was so damn cold your fingers would freeze to the tools when working on tractors,snowmobiles or our trucks. My dad put block heaters in all of our vehicles. If you forgot to plug in the vehicle,you had to put a clamp light under the hood for an hour,usually down by the starter. Before the block heater it was a 100 watt light bulb in a work light with a wool blanket over the engine. I remember frost would build up in the carburetor, then it would suck it in to the intake. You had to use ether to get the damn thing started. Especially the ford tractor.
In my early days I just loved florescent lights but hatted the turn on flashing. One day I was looking through the RS catalogue (as one did) and noticed the electronic starters. I replaced ever one I had and just loved them. It only ever struck once after about 2/3 seconds, noiseless and zero flicker. I still have a few in my bits box today. No idea why I keep them as I am 100% LED these days.
The old starters were abysmal! I once lived 50 metres from a 'corner shop' [Spar]. One morning I go on the air on 20m with my ham station and there are ENORMOUS clicks about every 0.7s across (as it turns out) every band. I scratched my head for a few hours (at work) and finally concluded it must be a light. Sony ICF7600D in hand I find a huge signal when outside the shop. Look in and presto! One of the tubes is flickering on and off. I went in and pointed out what was happening and luckily they changed it (the tube) right away [it helped that it even showed on TVs and I pointed out I would tell the whole neighbourhood that their TVs were being 'attacked' by the local shop!!!!]. Luckily, after a couple of occurances of this they fitted electronic starters and the problem more or less never re-occurred.
Back in the day I was using starters for making Christmas lights blink. You had to try quite a few starters until you got the desired effect and as the starter ages the frequency also change. It was very exciting. :D
So THAT's what causes the ends of the tubes to turn dark! Thanks, BC!
I never knew. It is like there is "welding" going on in there, when there shouldn't be.
Would the voltage at the zener diode be lower because the fluorescent tube is now lit and therefore, no voltage would charge the capacitor to turn the thyristor on again (and thus, it would not try again)?
But what if the tube does not light the first time?
+jaaasgoed I wonder whether this is just the point. Maybe a second starter cycle is intended, just not as frequently as with the mechanical version?
The Pulsestarter doesn't simply open when it's finished preheating - it opens and closes very rapidly over a half-second period, or until one of the openings causes the lamp to start. Also, the diode D1 (at least in my unit) is a peculiar one, with a ~3V forward voltage. This might help with some of your confusion with the circuit.
I was finally able to see what the name of that switch assembly was, and then you said the name of it. I have been wondering for some time what it was but never heard you put a name to it in the videos I have watched. Thank you Clive.
Finally understood the reason for the "high holding current"... When the drive to the thyristor is removed, it WON'T wait for the zero crossing, but will cease conducting while there is still current to provide a kick.
Great topic, these fluo lamps. They were a big mystery to me when I was a little kid and no one around to explain to me how they work. Unlike the so intuitive incandescent light bulbs😊
11:15 Technically speaking there's a different terminology used depending on application. Choke - to block RF and Ballast - to limit AC current, also typically ballast would be much bigger and have higher inductance.
I learn something from every video you do, BC. Thanks for increasing my knowledge.
I used to like charging those little caps up with 500 volts (with an insulation tester) and throwing them to people while saying 'here catch'. This was back in the 80's when you were still allowed to do bad things to people at work.
Rabbi Zyklon Brausebadstein when I first heard about that I was shocked.
Sorry I had to, I used to heard those stories. Unfortunately most people are already cautious when I throw things at them.
Rabbi Zyklon Brausebadstein or get them to hold on to your wind up 1000V Megger LORL Great fun....
Yep. Happened to me my first day at electronics school.
Or asking a fellow student to hold a granate and walk away with the pin.
And then after 20 times you had private lessons.
Yes we had a tough school in Aghanistan
In my electronics class, everyone just melted blobs of solder and catapulted them from the irons. We had no way of charging any capacitors because our teacher knew we would try that lol.
I think the regular paper actually looks better in the camera. no reflections
.
So THATS what those are! i saw a bunch scattered in the bed of a truck from this pawn shop and i couldnt figure out what they were. Thanks for this video (literally within a week of seeing them for the first time lol)
From what I gather the resistor below the transistor's base forms the bottom of a voltage divider which must account for why it works. I am more shocked to see an actual circuit with discrete components in that starter case than anything. All the ones I have torn open never had anything that complex in them. I think I even have an old one down the basement that has a removable starter that is resettable. I got that FL unit from a city worker where they used to keep the snowplow trucks -- apparently it is extra good at staying lit in our frigid sub zero temps. Good vid, Clive.
This video just answered every question i had when i was a kid
That was super informative Clive. I wanted to know how starters work since I was a kid but never got around to reading up on them.
Have you seen this video? It covers the technology in fluorescent lights. ruclips.net/video/qLaD11LITbQ/видео.html
Believe it or not my _other_ boss had a hand in this one. I say a hand, the design was done but needed tweaking. We got involved because they were being produced locally at the time by BG Electrical. Now my boss is very smart, and he struggled with it. It's a good demonstration of a design that's almost too clever for its own good.
Boss is on holiday right now and the job precedes electronic records so I don't know how much we have but I'll see what I can find.
I love this electronic Starters. They are so reliable and the tubes lasting for ever
Hi, Bigclive. Thanks for making this video.
I remember making a request for it ages ago.. Shortly after your 'sudden science - driving fluorescents' video was released a year or two ago.
Have always wanted to know how these work. Time to grab a beer, sit back, and be enlightened.
Keep up the brilliant videos. You're my favorite subscription :D
I've seen these starters in my childhood in the 80s when one broke. They all looked like the white plastic housings, but they did blink the lamps several times. Also after they were replaced, I haven't seen fluorescent tubes go on without prior blinking until the end of the 90s or even early 2000s.
The electronic fluorescent starter could work well as an April fool's - Wire it in series to a table light (assuming incandescent) and set up a candid camera. When the victim switches on the light, it goes out, leading them to replacing the "blown" bulb and of course the same with each spare bulb they try. I have wondered how they claim to increase tube life and indeed the longer warm-up period and single strike explains a lot. Another clear benefit is that the cutting off also saves electricity on failed tubes. With a standard starter, the ballast is effectively shorted with endless start attempts, consuming more power than with a working fluorescent tube.
Seán Byrne They are very effective at increasing tube life because of the mandatory preheat.
Where circular fluorescent tubes are used in ceiling lamps, they do not have guard rings on the cathodes, so the tube ends blacken very quickly. But with the electronic starter they hardly blacken at all.
On many tubes started by these, the phosphors in the tube wear out before the cathodes!
2:21 If the starter is a part of the circuit as drawn, why is it then possible to remove the starter, after the tube is lit ? That would make it an open circuit and no current would be able to flow ?
The starter is not in use after the tube is lit. It's open circuit and the voltage across the tube is not enough to make it glow.
@@bigclivedotcom Yes but as you draw the starter in series, removing the starter should break the circuit, would it not ?
This is what i dont understand. There is no path for the current to flow between the live and neutral if there is no connection in the starter.
@@JohnDoe-bd5sz When lit the current flows through the tube and not the starter circuit
@@bigclivedotcom Aah, i think i see it now. It's because i thought that there should be a closed circuit, thru the 2 coils inside the flourecent tube.
The circuit when the tube is lit, is actually going from the top pin of one side, through the tube to the other.
Sorry man, i just had to understand it :)
Really love your videos, keep up the good work.
Hello Clive, I enjoy the content of your videos.
There is a large AC ripple content appearing on the bridge output , this being unsmoothed ., the positive going pulses appear at the transistor base via the 47 mfd and 56k, pumping up to Vbe, thus keeping the transistor on after it initially triggers. It cannot turn on prior to the initial trigger because the 47mfd/56k time constant is longer than the 15k/1mfd. Once the tube fires, there is no voltage available through the zener, the SCR remains off.
If the tube doesnt fire, the ripple voltage continuously removes gate voltage via the transistor shorting the 1 mfd until the power is cycled.
Its a bit of a trick circuit to be sure......
Ah thank you! I think I get it now.
I watched the video and read the comments explaining it further and I didn’t honestly understand it until I read your comment.
I felt like I was the only person that didn’t get it still after reading the further explanations.
I can’t believe I am the first person to give you a thumbs up 👍
If the 24k resistor was lower value then that would steal the current from flowing into the base and cause the transistor to turn off, thus allow multiple attempts at starting the tube?
Well this brings back memories of the 70 ish I was about 14 and was amazed to discover that putting a starter and a light bulb in series, the bulb would flash. So I started building disco lights for friends. However my parents soon put a stop on my electrical explotes, not on safety grounds but because my testing was messing up their tv watching downstairs with rf interference.
This reminds me the number of June 1982 of elektor magazine. They (and me!) used a TIC106D and the circuit still works today.
wow Mr Clive, my fount of knowledge on the dark art of electronics, flummoxed by the recipe for this spell, tubus onestrikus. Broken Britain, I tell you.
I've been mulling it over in my mind and I'd guess that even when a lamp has failed to strike the thyristor will fire briefly to keep the capacitor topped up.
A very good explanation
I was kid when i learned how to turn on fluorescent tubes without straters only with a push button or just 2 wires 😂
Through all of my childhood, a classical starter like that was the thing that kept the string of Christmas lights blinking on the tree... :)
That was probably a bi metal flasher built in to a case the same as a starter.
From the TN22 data sheet. It says on page 8 " If the lamp is not ignited after several attempts, the starter circuit can automatically stop the ignition sequence." How does this work? I see how the sequence will start again after a failed attempt. Just not how it will automatically stop the process after several failed attempts.
How is the darlington getting switched on if it has only one diode drop on the base?
Is ist because of the diode drop being rather high due to the high current trough the thyristor?
+MrJumpersun I think it may be the higher drop due to current.
Great video. What do you call the mains connecter that you connected the light up to. I've been trying to find them, but don't know what they are called. Anyone know where I can get one?
I think the zener diode prevents the circuit from retriggering. As you said, the tube voltage when it is ON isn't 220V. Or did I get that wrong?
So, the zener voltage is high enough to prevent gate current on the tiristor when the lamp is already ON. This one should retrigger I think.
he is talking if the tube failed to turn on why does it not try to turn it on again
OK, I got it wrong :) It makes sense that I get things wrong.
i agree he did not explaine it clearly
i remember cold start and rapid start starters. also for the army we had some florescent lights that you could turn on a small tungsten light to warm it up. Physically warm up the florescent tube.
The early dimmable fluorescent lights had a tungsten lamp to provide continuous current to the cathode heaters and make them dim more stably over a wider range.
6:58 Hehe. Memories. I when I was 12 I think, I hooked a little bit bigger neon glow lamp up to the mains without resistor. Man. I got scared. Little glass shards all ober the workbench and floor. I should have known what I was doing. Thank you for sharing your knowledge and good night from Germany.
Here is how I think this circuit works.
The gate-cathode junction of the thyristor conducts just like a diode and the thyristor will not fire if the gate current is low. When the transistor base voltage drops by discharging the capacitor, the transistor turns off and the gate voltage rises, recharging the capacitor. The transistor keeps the gate voltage below the threshold.
The gate current (capacitor charging + transitor base + diode) must be kept below the threshold to keep the thyristor off (for lower consumption). In the case of the gate current of the thyristor is above the threshold it will conduct from anode to cathode and will recharge the capacitor the same way the gate-cathode junction would.
I think the reason it only tries once is the 47 uF cap on the transistor via the resistor, the 82 and 24k providing a discharge path when power is turned off. Once that cap charges the current flows through the transistor instead and not providing a gate cathode drop high enough to trigger the SCR and perhaps leakage from Collector base when the transistor is on is enough to keep the cap charged.
As I see it:
The fluorescent lamp should get lit by the coil spike after the thyristor gets shut off.
After that the voltage over the circuit is low enough to prevent a restart, the zener doesn't provide current.
If the lamp shouldn't start the voltage rises high enough to conduct the zener again and the cycle starts over once more. The R2, R3 and R4 should be dimensioned such that the darlington doesn't conduct anymore at a restart.
Now I have a question: the darlington input needs 2x 0.65 Volts, is the series D in the main circuit a version with a higher voltage drop?
Used to make disco lights using a starter on each one off theses RED GREEN BLUE spotlights and there also great for flashing Christmas lights did you know if you alter the value of the capacitor across the flasher you get different flash rates
The Darlington has 2 Vbe drops on the base, so there is a question as to how the Darlington turns on in the first place, given that it is driven by the forward bias voltage across the diode in series with the thyristor. The Vf of the diode should be less than or very close to the base on voltage of the Darlington. so is the series diode a sense and the diagram has it the wrong way round or is it a diode with a high Vf?
The high Darlington gain means it's base current will be very low, so the charge on the base capacitor will be able to maintain the clamp on condition for some time, particularly if the capacitor charge is not able to flow back through the diode in series with the thyristor. This again point to a high Vf for this diode or more likely that it is a reversed biased Zener diode with a Vz greater than the two standard Vbe drops of the Darlington. It is like therefore that thyristor triggers more than once, but with a very long period between trigger points. As there is not any hysteresis in the Darlington circuit, it is likely that after the initial triggering that charges the timing capacitor, subsequent triggering a will be of a very short duration ( maybe just a mains half cycle), sufficient to recharge the capacitor and reactivate the clamp. Knowing the excess voltage across the charged capacitor and the Darlington base current it should be possible to calculate the trigger period. The resistors connected across the capacitor likely control the trigger period so that the circuit will trigger reliable each time the mains is turned on.
In the case of the recommended circuit that uses a second thyristor rather than a Darlington as the clamp, the clamp thyristor will fire just once as C1 will maintain the clamp thyristor hold current through the zero voltage of the mains cycle.
bigclive, i suspect the transistor shorts out the 1uf capacitor thus drags the operating voltage down for the power supply and then is held low. hence the thyristor cannot be triggered again regardless of the power supply coming into the starter
a starter was the "poor man's disco lights" back in the 80s hehe, we did this a lot
...or Christmas tree lights :)
right, and make more strings with a starter in each string, will give a nice christmas light disco hehe
Are there different rated starters for specific wattage tubes? We have a 2ft tube that blinks like mad when first turned on. I replaced the tube and the starter but it still behaves the same.
Yes, they all have the range of wattage of the lamp they can work with.
Compact tube florescent have a much lower range than the larger tubes but that should be printed on them.
As here: static.bltdirect.com/cache/images/Fluorescent-Tube-Starter-4-65-Watt-1-700x625.jpg
Oliver Dawson yes s10 starters for say 4f and 5f tubes then you have s2 starters for fittings with (2x18w) 2x2f tubes not sure how it is in the US. Hope this helps from an aussie sparky
Thank you all for your help. I think the tube is 18Watt. the starter is a cheapo universal one but I'll check which type.
Back in the 70's (in Iraq), I made a poor man's Sound-To-Light unit using starters & different coloured bulbs...
It randomly flashed those on & off and had no connection to the music or sound, but it was fun, and I lived to tell the tale...
Could you use one of these for an automatic cut out timer on a start capacitor for an electric motor?
+Paul Duffy you can get simple PTC thermistors for that application.
Interesting, would you also take to bits those compact fluorescent bulbs ?
If I am understanding correctly, this is basically an automatic version of the manual red "start" button on some desk fluorescent lights?
I do remember my father's old shop having the lights flicker when you turn on the switch. Good old magnetic ballasts.
I remember seeing several cards of starters in a local home center about a month ago.
Basically, yes, but I would never have thought of the term "automatic" for those glow light starters that are still quite commonly used over here.
It wasn't until copper became so expensive that magentic ballasts started fall out of favour and were replaced with electronic ones in new fixtures. But there are still loads of magnetic ballasts around.
I'm guessing the the leakage current through the thyristor allows a small amount to current to flow after it's attempted to start the tube. Since the transistor is a darlington an extremely small amount of base current would allow the collector to stay below the threshold voltage of the thyristor and never letting the trigger current flow into the gate.
I had heard quite some time ago that flourescent tubes had an expected lifetime that was based on the number of times you started it up, and it was never quite clear to me why this should be, until you explained it in this video. I'm guessing that this is the reason that a lot of commercial properties like large office buildings are left illuminated all night long in places like New York City, as opposed to turning the lights off. Their cost for the electricity would have been less than having to replace the bulbs more often, I guess.
Here's a great one for ya. My aunt brought by a pool pump for me to fix. She said it got wet and wouldn't turn back on.I just told her it's too complicated to fix. People don't get safety mechanisms.
What an amazing video sharing! ..... I wish my science physics teacher able to explain in the same manner (during my school days)
One of the joys of RUclips is that there are a lot of really good educational channels which are not only enjoyable to watch, but are free too. It's what the Internet is for.
Clive really knows his stuff!
It's fascinating!! :-)
When the transistors conducts, it is discharging the (charged) 1 uF capacitor.
This might cause a short peak with a high current. Will the transistor survive this? (No current limiting resistor!)
The light-bulb-on-flourescent-starter is an old favourite of mine for Halloween displays. Cheap and dirty flickering. :)
i have an old late 80's salad fridge from a resturant i work from and it uses those things all 3 tubes. nice to know more about them as i always wondered one of them is original glass tube one in a tin shell but other ones were replaced by me when unit was still functioning years later before retired it and taken it home. i do like the clicking though it just sounds neat specially when tube flickers alot sure it ruins life of it but i dont know just sound and seeing it do that is fun
You've got the way a thyristor is triggered the wrong way round - the Darlington shunts the gate voltage here, stopping the the thyristor triggering. Given long enough the cap on the base will discharge and the starter will have another go at striking the tube - there's a clue in R4 labelled 'Reset control' on the datasheet cct.
And now I've looked at the full datasheet that is what happens.
However there's there's a problem with the ccts as shown if I'm thinking straight. If the diode (D1) in series with the thyristor is a normal one its forward voltage won't be enough to turn on a Darlington and I'd not like to bet it would reliably turn on a thyristor either.
Edit: When hand-drawing a Darlington I just put two arrows on the emitter.
Could a capacitor be used in place of the ballast? inductive dropper circuit instead of capacitive dropper?
Only thing i can think of is a slight leakage that keeps the cap alive
Many years ago i was asked to put a warning light on a freezer room door (room was in a cold room), so if the door wasn't closed properly they would know from the corridor, i installed a sealed industrial limit switch in the door, and fed it out to a red bulkhead fitting, to make it more obvious i wanted to use a flasher unit, but then i thought about using a starter, just the normal mechanical (glow type), but it worked well for many years, and because of the random flashing it was much more annoying and obvious.
Always wondered the same thing about those starters back in the days before electronic balasts.
In the US we have old desk lamps that use Manual starters. The Japanese versions of them are even simpler. I will describe the Japanese makes here, but the American models simply have a latch in the off button added that is unlatched when the start button is pressed.
When the desk lamp is plugged into the power outlet the line voltage is present across the lamp and ballast, but the lamp is not lit since a starting cycle has not occurred (note American units the off switch is usually still latched open). When the on button is pressed the start contacts are closed (dual tube units have two sets of contacts here). The on button is held in until the ends of the tube glow and then is released. If the tube doesn't start (either due to dodgy on button or not being held down long enough this cycle can be repeated. When the light is on the tube continues to conduct until the power is interrupted. When the power is interrupted (ether externally, by someone removing a tube, or by the off button for a few seconds) the lamps cool down enough that they will no longer conduct.
The circuit in the lamps is rather simple. The off button is a normally closed momentary (latched in the American versions) pushbutton and is in series with the entire circuit. The on button contains a set of contacts for each tube and these contacts are placed where the starter is in the circuit.
What's the big deal between latched and unlatched off buttons. The unlatched off button only breaks the potential from the circuit when held down. The tube can still be induced into a dim glowing state or started by external means (static discharge, discharge from a piezo ignitor, nearby lightning strike which is more common on the 14 inch tubes, CRT degaussing within a few inches, etc). The latched version keeps the normally closed switch open until the on button is pressed.
Now these designs are not common outside of 100 to 127 volt countries as the tubes must be in series to prevent instant starting with the OCV of the mains in 220 to 240 volt countries. In these countries a standard automatic switchstart circuit is used.
And for what its worth some of the cheaper ballasts have or had that same circuit built into them from what Ive seen. Obviously no longer removable, so if it takes a dump the whole ballast was trash. And yeah lol remember those back in my school on some of the desks since it was a historical site from the mid 1800's. Had to push that SOB button for a while to get light sometimes.
any help off any1 plz.....i hav a 18v AC input and get a 23v dc zap from a 40v 2200uf capacitor is there anyway i can get a bigger zap from this...would a darlington transistor setup help or is there not enough info here to help and im just being a noob....thx for ur time if u read this
Once the Darlington pair transistor fires the collapsing choke field produces a Back EMF discharge that is enough for the fluoro to conduct resulting in the voltage drop across the fluoro is low enough that the Zener does not conduct and cause a re-trigger the heater element circuit. Once the flouro arc is struck there are enough charged particles in the tube for the reverse cycle to reignite the arc.
Looks like a better design than the ones i bought some years ago. First one i got worked fine, so i bought another ten or so. All of which failed within half a year, burning out some almost-new tubes and one even catching fire from a cold solder joint arcing.
These had a relay inside and used a single diode to effectively saturate the ballast core with DC current to allow for a larger preheating current (which burns out the tubes and causes a really loud buzzing noise while starting), as for voltage detection they used a varistor (which is not intended for anything other than surge absorption and did burn out). I didnt bother to reverse engineer further, only replacing all the fixtures with electronic ballasts that finally work properly.
Damn dude, I just bought 6 of them today for about 50 cents each, now I'm carefully considering again for the application, thanks a lot for your experiment , really appreciated.
I don't know much about circuitry but I would assume the Darlington transistor is supposed to turn on and off, and then the track with the 1uF capacitor is just where the current goes.
Why is the arc struck inside the fluorescent tube and not in the neon bulb?
I'm not understanding how those little bulb starts (with the bimetallic strip) work. How does current flow through them (to heat up the strip) before there's a path across them? I know it could arc across, but if that were possible how would the circuit ever open? Also, why do the strips cool down once they make contact (and current is flowing through them)?
There's a gas inside that conducts like a neon lamp.
@@bigclivedotcom Thank you. So that causes the neon to heat up which bends the strip, right? I was thinking the current flowing through the strip is what makes it heat up and couldn't figure why it could cool once it completed the circuit.
I don't think the diode that is in series with the main thyristor is a zener. The band on it is to the negative rail. If it were being used as a zener it would be the other way round with the band to the thyristor cathode. It could simply be that this diode's forward voltage is high enough when the heaters are on that it will exceed the voltage required to bias the darlington on (after the time delay) and reverse bias the main thyristor, turning it off even thought it still has a voltage across it's anode-cathode.
If the tube doesn't strike at this point, I can't see how the starter is going to latch off. The 47uF timing capacitor is going to discharge via the diode (without the heater current it's forward voltage will be lower than that needed to bias the darlington on) and the "reset" resistor. I suspect it just keeps switching on and off, giving the tube further chances to strike.
It would be interesting to watch what happens on a scope with a broken tube - after having taken precautions as a scope's probes are usually referenced to earth (and therefore the neutral in .uk).
How does the darlington transistor turn on in the first place ?
Its only got one diode drop to supply its 2 x base-emitter diodes and this diode drop is even voltage divided by the 82K-56K resistor divider.
IMHO the diode ist not a diode. It must be a zenerdiode to make the circuit work.
Something like a 6.8V zenerdiode, as the 47µF must have a charge to keep the darlington on long enough to discharge the 1µF capacitor and sink away this 1µF repeated charging current.
My guess is that you got a mis-read on the darlington transistor, and it actually is an SCR. Try checking the part number on it again. Otherwise, excellent video and great explanation. Thanks!
It's obviosly that the 47uF capacitor that charges a few seconds after the thyristor is triggered then the darlington transistor will shunt the thyristor's gate, since the transistor is a darlington it uses very little current so the capacitor should discharge slowly, I suspect that after the capacitor is depleted it should retrigger the thyristor again. I hope i got it right. Cheers :)
That's how I interpret it as well. I can't see how else it would work.
ciprianwiner yes that's right the Darlington could be held off from retriggering the thyristor by a tiny current even putting your finger on the open Base would hold it off so i guess it would take weeks for the capacitor to lose every last nA. ....
I don't see how that would work. The 47µF cap through a 56K resistor has an RC time constant of only 2.6 seconds - and it was only charged to about 0.7V to begin with. For that matter, this MPSA14 darlington has a Vbe of 2V, how does it ever conduct in the first place with the base shunted by the diode to 0.7V? Very odd indeed.
That had me puzzled too but it was the only explaination i got, maybe the diode is not a regular diode? or Clive had it draw incorrectly, maybe Clive could check the forward drop across that diode? Who knows, maybe it's even an actual zener diode and he didn't check it. Cheers :)
Once the fluorescent has fired there is going to be no voltage at the transistor collector that's why that 170v zener is there? Therefore there is no voltage at the gate of the SCR. The transistor is there to take the gate away if tube fails to strike within a certain time, it should reset itself? (Edit) the original circuit using the scr to control the gate would need a power cycle to reset.
Are you sure it only fires once? Might just be that the capacitor holding the darlington high last for a minute or two?
The MPSA14 is a germanium transistor with junction voltage of 0.15 to 0.2v.
Once the tube starts the voltage across the tube is square (AC peaks clamped at about 100v) & the zener does not conduct, therefore no further conduction of main thyristor. But if by any chance tube does not strike then re-striking does happen.
In Old tubes the clamped voltage is beyond 140v. Tubes with still higher clamp voltage has danger of bursting.
I used to use the old type starters to flash the old chistmas tree lights back in 60s/70s.
Hi.
Could you please reverse engineer a crt circuit (tv or monitor) from mains input to flyback
I've been trying to figure out how they work, they seems to drive the flyback HV output so much more efficient than royer or zvs circuits , which always needs massive heatsinks, and still blows the transistors or mosfets on regular basis
The flyback circuitry in traditional CRT displays is very evolved and fine tuned for reliability. The circuits used in it are generally mass produced for the task as are the transformers.
It's a simple capacitive pull down switch that's being used as a timer in this instance. Once the capacitor get's enough charge it's no longer pulling the base/gate pin to it's active voltage or vice versa. Think of the dual LED flasher circuit and how it uses transistors and capacitors to switch back and fourth. This works on essentially half that circuit. Since it has nothing to reset it back the other way, it just stays off.
I'm baffled how the transistor gets turned on, since a darlington has 2x Vbe, and the drive to it is fed by a single diode drop - unless that is not an ordinary diode!
The "R4" is defined as the reset, I'm guessing it's meant to shunt the leakage to lower the voltage to the point where the switch off SCR / transistor unlatches.
I guess the value is too high, with a lower resistor there, it may retrigger.
+Matthew Day That did go through my mind too. I may desolder one end to see if it's a different diode.
Just read about another system, the half a second "fast starter", though it sounds somewhat abusive of the system.
users.tpg.com.au/pschamb/light.html
Described as using "DC heating" and producing a characteristic buzz and magnetic disturbance, I instantly figured out the trick - while there would be a 50% disadvantage in only using half wave control, more power would reach the heaters as the ballast would present only resistance. The other half cycle could be used to continuously detect tube firing.
It would be a rather brutal system though, and I can't see it being good for the life of tube or ballast
See how neat you make your videos, amazing !! thanks for the video
I don't think I've seen one done before but what would make a great reverse engineering item and interesting to see the explanation on how they work would be a HF electronic ballast for fluorescent tubes if you might consider it Clive cheers Sean
@bigclivedotcom Well.. How does a fluorescent ballasts work then?
Clive any possibility of showing the circuitry of flourescent emergency lights which incorporates an inverter and batteries along with the ballast. 🍻 cheers.
Fluorescent Experts I have a question. How many volts on a 4 foot tube? Can you test the voltage from a ballast? If so how.
what about magnetic rapid start and slimline ballasts?
I have never ever had an electronic lighter failing to light the tubes. They work like, Amazingly good! And they last for decays! My oldest one are like 20 years old, or more!
Using an old type starter on a incandescent bulb with red gel is a grate fire lighting effect. esp shining though a slow running fan.
So, the tiny amount of current flowing through the "off" thyristor (which annoys you if you have a sensitive led which tries to start on it after loading its caps)
keeps the transistor active enough to prevent the thyristor from starting... interesting use of something i always viewed as a bad/negative aspect of Thyristors.
( i always hated that you cant really switch off a thyristor dimmer without another mechanical switch to really cut off the leakage current)
I thought you had the autoranging version of that DMM Clive. Been looking for one with decent range of cap testing
+Chris Leech I have the autorange version too, but like the huge display on the manual one.
The high holding current is to allow for a decent voltage pulse to be generated by the choke. If it had a holding current of, say, 1mA it would open in the moment wehen the choke would carry only 1mA and thus had no stored energy left to strike the tube. (Opposite reason of why you switch off huge tranformers right at the zero crossing of the current.)
Nice video! I like a lot reverse engineering and I am trying to find the transmittion protocol between a generic parking sensor module for a car from China and his receiver.The communication is made through 3 wire,Ibelive that is serial communication but I don't have an oscilloscope to identify the sequence.I tried with a CH340 usb to serial converter but I cannot identify the baud rate.The module is from China is around 12$. Please help me if you can.Thank you.
Hey I'm in college right now finishing my developmental classes. When I'm done I wanted to get Into repairing electronics and stuff. What would that profession be named? Also how could I start learning now?
Look for a job doing maintenance.
3:04 Why does it cool down? These videos are great. Electricity is just so strange to me. Cheers.
Electricity is not flowing through the gas but through metal which has low resistance
@@Boz1211111 Why doesn't the low resistance make more electricity flow through it, making it get hot again? I know I'm wrong, but I dont get why.