Can someone explain this strange AC circuit  - Page 1
Forum section: electronics / projects

author: Dzoro
author_rank: Contributor
timestamp: January 04, 2023, 12:09:17 am
content: Hello guys i have a questioni need to know how this circuit works because when i probe it with an osciloscope i get some peaks of voltage and nothing usableAlso can i implemet digital controll with arduino or esp 32 to controll the 100K pottentiometer without changing the circuit because it is critical to stay like it isAlso one more question--the capacitor C3 is a motor starter capacitor and when i change it from 20uF to let say 30uF the sound that comes from it is like deeper and when i decrease the capacitance to 10uF the sound coming from it is softerAlso can someone explain why the imput cable that is rated for 2KW a big chunky cable is getting hot and when i measure the circuit with a power meter the circuit draws about 150Watss max when the pottentiometer is turned to maximumSooo strangealso i tried diffrent power cables,all of them are getting hot-some less,some moreAlso i cant tell you what i use this circuit forAll i can tell you is that you put it in the wall socket on 220AC and calibrate the potThe circuit is down below one is in pdf one in pngThanks Dzoro

author: themadhippy
author_rank: Super Contributor
timestamp: January 04, 2023, 01:13:02 am
content: Are yo sure its wired across live and neutral as all its doing is shorting them our,if you bypass c3 it would make a good fuse tester

author: bdunham7
author_rank: Super Contributor
timestamp: January 04, 2023, 02:38:49 am
content: A few decades ago I came up with the brilliant idea of a 'negative power factor' device that would adjustably compensate for the current lag of inductive motors, intended to be used in appliances and machines to keep their PF as close to one as possible. It worked sort of like this circuit. I thought I was a genius, I could get it patented and I'd be rich in no time.In short order I realized I was an idiot and the problem seemed obvious in retrospect. Your capacitor has a reactive impedance of ~160 ohms @ 50Hz, so you might expect about 1.5A of reactive current to flow with not very much power. And so it would if the triac were always on. However, the capacitor doesn't react to frequency, at least not to the period. It reacts to dV/dt or the frequency spectrum of whatever voltage is applied across it. When you delay turning on the triac, there is a huge spike as it turns on, the current isn't neatly 90 degrees out of phase at all. It's a spiky, noisy mess. I expected that, sort of, because I knew that triac dimmers were electrically and audibly noisy. However this was the sort of spiky mess that caused the triac to spit its guts across the room with a nice blue flash.The only scope I had at the time was a Scopemeter and I didn't save any pictures. I did see just enough to know that it wasn't helping my PF. The only way I can think of (now) to make this work would be using multiple capacitors and better triacs (alternistors, probably) in parallel and turning specific combinations of them completely on or completely off. Or you could use power MOSFETs or in big devices, IGBTs. I see you have a 4-quadrant triac there, but I can't imagine this works very nicely in the intermediate settings.You get a warm cord but only 150W power because your RMS current is high but your PF is low. Your RMS current is likely high because your peak current is very high. And your PF is low not only due to phase-angle (current leading) but also (and probably mostly) harmonics.Why can't you tell us what you are doing? That doesn't look very top-secret to me.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 04, 2023, 03:04:21 am
content: It looks like a primitive sort of PLC transmitter, similar to what UPB uses.Quote from: Dzoro on January 04, 2023, 12:09:17 amReplace the potentiometer with a LDR and shine a LED on it, using PWM to vary its brightness. Basically making an AC output optoisolator so your logic stays isolated from the mains.

author: Dzoro
author_rank: Contributor
timestamp: January 04, 2023, 04:40:57 am
content: Yes i am sure i made around 100 circuits

author: Dzoro
author_rank: Contributor
timestamp: January 04, 2023, 04:43:11 am
content: I can tell only you that because you clearly understand the circuit far more than i doSo you can help me make it better but i will need to contact you diffrentlyNot here

author: Dzoro
author_rank: Contributor
timestamp: January 04, 2023, 04:49:00 am
content: That is a very intresting idea i havent thought about thatBut i think that it is not going to be stable enough because of all the sorounding lightsI will have to make my own enclosed ldr optoisolated chipBecause i need to controll it with like a 100 steps ,like those digital pottentiometers that work with arduinoOr try to find some chip that already exist that is doing thatBut it is a briliant ideaThanks alot

author: CaptDon
author_rank: Super Contributor
timestamp: January 04, 2023, 08:13:07 pm
content: Blah, Blah, Blah I can't tell you what I do with this circuit?Any fool knows what you are doing with it. It probably as an added benefit unknown to you is creating all kinds of spikes on the line potentially damaging expensive equipment plugged into the same line. Of course a bigger capacitor is raspy and a smaller one 'quieter' as this directly effects the spike current when the triac fires. We once called this a Pandora's box and if you drop that capacitor to about 2uf you can really start to blow up sensitive devices on the same outlet due to ringing over 1000 volts peak. Don't bother to tell us what you do with it as we can already tell you what you do with it.

author: Dzoro
author_rank: Contributor
timestamp: January 04, 2023, 09:08:31 pm
content: First of all don't categorise people without knowing anythingSecond of all why an electronics enthusiast would want to destroy other people expensive equipment or gadgets or appliancesI just don't get itAnd also it is illegal to do stuff like thatAnd please don't come to topics to categorise without helping or just normal chatting.

author: wraper
author_rank: Unknown
timestamp: January 04, 2023, 09:23:14 pm
content: As it is shown, it's wasting power within electrical grid and generating interference in adjustable way. Sort of dimmer but with capacitor as reactive load. Also C3 and triac likely will not last long due to very high peak currents. Power switch location is weird.

author: Benta
author_rank: Super Contributor
timestamp: January 04, 2023, 09:25:12 pm
content: Don't worry about CapnDon, he carries a major chip on his shoulder and likes to shout at people.The circuit looks like a normal Triac phase-angle control to me. The firing control is a bit more elaborate than usual, probably for tailoring the potmeter response.Having it in series with an induction motor start/run winding would make sense for controlling a "single-phase" motor.Placing in directly in a 230V receptacle is futile.

author: mikerj
author_rank: Super Contributor
timestamp: January 04, 2023, 09:50:03 pm
content: Quote from: Benta on January 04, 2023, 09:25:12 pmOP has already confirmed it's wired straight to live and neutral, the only link to motors is that he's using a motor run capacitor for C3. I suspect CapnDon's cynicism is well placed in this instance.

author: Benta
author_rank: Super Contributor
timestamp: January 04, 2023, 10:04:51 pm
content: Quote from: mikerj on January 04, 2023, 09:50:03 pmRereading this whole thing again, I'm afraid you're right.This smells a lot of "Snake Oil" power-saving nonsense.Oh well, there's one born every minute (free from P.T. Barnum).

author: bdunham7
author_rank: Super Contributor
timestamp: January 04, 2023, 10:56:11 pm
content: Quote from: Dzoro on January 04, 2023, 04:43:11 amYou are welcome to PM me through the forum if you like. However, I don't see how I could 'improve' this without more or less starting over. 4 triacs, 4 capacitors of 2,4,8 and 16uF, 4 opto-isoated triac drivers and you would have a 4-bit system that could do 2 to 30uF. And even then I don't know how quiet that would be.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 05, 2023, 01:52:17 am
content: Quote from: wraper on January 04, 2023, 09:23:14 pmBy varying the phase angle, it can be used to transmit data. It would be a slow rate, but a few tens to hundreds of bits per second is plenty for remote controlling stuff.Another possibility is a test fixture to determine how resistant AFCIs are to false trips caused by repetitive impulse noise. If one just wants to generate very wide, very chaotic noise, a spark gap transmitter would be far more effective. (And AFCIs are supposed to detect such noise generated by arcing.)

author: bdunham7
author_rank: Super Contributor
timestamp: January 05, 2023, 04:07:07 am
content: Quote from: NiHaoMike on January 05, 2023, 01:52:17 amWhile a crude circuit like this might seem attractively simple to implement, what about the reciever? How do you acquire and decode that data?Back in the day, perhaps you could use it to make your upstairs neighbors television lose its vertical hold.

author: CaptDon
author_rank: Super Contributor
timestamp: January 05, 2023, 02:32:19 pm
content: Actually, we didn't use it to 'intentionally destroy equipment'. We used 'Pandora's Box' to generate the worst of the worst industrial switching noise and prove that our industrial ladder logic controller could survive without having failures or nuisance reboots!! Saying "I can't tell you what I use it for" is never a good thing.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 05, 2023, 02:44:09 pm
content: Quote from: bdunham7 on January 05, 2023, 04:07:07 amUPB measures the time between the zero crossing and the impulse. It's far more resistant to EMI than its main competitor at the time, X10.

author: MarkS
author_rank: Unknown
timestamp: January 08, 2023, 04:47:29 am
content: If this is what we think it is, wouldn't it be better suited in the Dodgy Technology forum?

author: Terry Bites
author_rank: Super Contributor
timestamp: January 08, 2023, 11:07:38 am
content: I think its wierd Power Factor Corrector. Connect an indcutive load and see if it reacts (ho ho).It looks like a deathtrap to me. I imagine it designer decided to use lower voltage 33n caps.I don't get the purpose of the 15k. Tweaking the knob changes phi from 30' up to 80'.