It's another mystery high voltage item from eBay and as often with these devices, there was just no information. I Initially thought it was going to be 120 volt or 240 volts on arrival. it actually has it in Boston that it says output 12 KV input 1.5 to 3 volts. And to be fair, it does have red and black leads, but it also has these green and yellow leads with another black wire come out and the two high voltage connectors.

The listing did show what was inside which is good and if I pop the cover off then it reveals two high voltage Transformers and I. Initially thought that because there's only two high voltage leads, that perhaps they had them both in series because sometimes they do that to create a higher voltage and reduce the voltage across each of the Transformers but there's also this little Transformer here that I speculated thinking initially it was 240 at night before separation of our control signal feedback with these wires. or it might be some sort of a step up circuit if it was low voltage and it is a step up circuit for low voltage. and if I take this out because it was originally potted in with a sort of silicone rubber oh, is it going to come out now it is a fairly tight fit.

When you look at the back, it's got some very odd circuitry and having taken out I did try it and didn't really have much luck. So I think it's time to reverse engineer it. so let's cut straight to the Chase and I'll show you the circuit board. Well, I'll just reverse engineer I'll take a picture and we'll see what the circuitry looks like one moment, please.

Well, that is odd. It's using clever things in the morning. What happens when they use clever tricks? It makes it much more complicated to reverse engineer because things are doubling up. So I Well, I'll show you going first.

Uh, we're in advance that because this is sparking, I'll Zoom down a bit. I'll probably have to turn the light off I don't even know sure with the light off, but uh, we've got two wires, yellow and green we've got. the black wire is turns out to have double function. It's common with the supply black wire the common negative and it acts as the common for the spark.

but we also have these two control wires and it turns out it's a dual circuit. So if I connect this wire and our warning: Advance there may be sparking noises, slight sparking noise, actually no space that apart. Make sure I'm just going to get those wires away from there. So I Don't get a zap much as you want me to get a zap.

Do it. Electro Boom. Style Let's see if it really is there. Suitably high voltage.

Okay, so you touch, agreement on and one is sparking. You're probably not going to see that yet. Uh, you touch the lemon and the other one. Sparks right? Tell you what.

I'm going to turn the light off one moment, please. The lights are off. So this is the yellow socket. so it's sparked in the left hand side, then the green circuit.

It's spark in the right hand side. What happens if I connect both at once. Lots of sparking from where we're actually holding these on. Am I Going to get a shock at some point? Probably.

Oh, we're actually getting bored. That's interesting to know, right? The light is coming back. Watch your eyes. It's time to see the schematic.

The light is back, and we're ready to continue. for reference: At Three Volts, the current consumption was just 300 milliamps. At 1.5 volts, it was 200 milliamps and the spark was notably slower. If we take a look at the circuit board, the main components are the two have: Ocean Transformers this little boost transformer with a transistor next to I Haven't seen the value of the transistor yet because it's heavily lacquered, which hides its value.

I'll have to take out the circuit board to see what that is. We've got a sideak, a diode, couple of resistors, and a capacitor rated about 680 nanofarad I think that is um on the circuit board itself. Good generous space from the high voltage. It's doing kind of double duty here.

Uh, there's the capacitor that charges up via this diode, which I think is a 1n4007 I can see the one end bit so I'll just make a guess. that's a sort of the highest standard voltage rating of those you get. We've got a sideak going to the negative, but notice the air, the negative is actually going out. So to complete the circuit, you actually have to physically.

uh, well, in this case of this, for the feedback, you have to physically actually Bridge one of the green or yet, uh, yellows down to the negative real. And that basically enables it because up to that point, it draws virtually no current. Well, no current, measurable current because there is no path. You know what? I Think: We'll just skip straight to this schematic.

That's the best thing because it's going to make it much simpler than looking at the back of a circuit board. The schematic, right? So look at this. We have a PNP transistor and we've basically got a standard feedback. The orange indicates one Transformer that's a little um Transformer there.

And if you've just took this connection directly to the zero volt realm, that would form a sort of feedback oscillator where this is the feedback winding feedback. This is the primary primary and this is the secondary and in doing that, it would start this. It would start oscillating and uh, when it did that, it would step the voltage up and then charge this capacitor with respect to ground. But there is no direct ground connection until you push one of those buttons.

But it would start charging that capacitor up until this side act. A little extra line to be drawn in here for the Psyduck uh clamp. Now the side hack is basically a bi-directional component that has a voltage threshold. It's used in a lot of igniter circuits and once the voltage threshold has reached me by about 200 volts, it suddenly clamps on and shunts, causing a sudden current pulse until the current through it flows to reduces to close to zero and then it will shut back off again.

So the operation of the circuit is this. when you press one of the buttons on the unit that Bridges the green or yellow to the black terminal which is connected to the chassis which is also the spark return. It then completes the circuit through. For this, the the feedback socket can then actually find a path through the primary.

Let's call this primary because that's what it is and second array primary of the two high voltage Transformers. So when you push that button, current flows and it basically starts uh, the circuit oscillating, charge the voltage up on this capacitor until the side act operates. Now there is a path because you're holding that button and basically selecting that coil, there is a path uh for this capacitor a to charge up and then B for when this side act fires and shunts that, it dumps the energy in that capacitor in a closed loop and basically fires a lot of current through this primary and produces a high voltage in the second, Recruiting the spark. If you push the other button, it also enables it.

But uh, this time because this is the call that's referenced to the zero volt reel, it's the one that will spark when you see it like this. It's very, very simple. When you actually try reverse engine circuit board, it is not. It was quite hard to draw this schematic out.

It took a few efforts to get in a sensible Style And there's a two Meg Ohm Resistor Just designed to discharge any residual charge on this capacitor. Although having said that, when you let go the button, it's not really going to do that, is it? I Suppose it could find a path back through the transistor. and there's also this Uh resistor here which limits the current in the feedback circuit and a little 2.2 nanofard capacitor. That's it.

Uh, interesting module. Is there anything else I can really say about this? Yes, there is. I Shall uh pop the cylinder on right now and I shall whip that transistor out and we'll see what that little transistor is in there. Is this capacitor discharged? Yes, it is.

Um. and we'll I'll try and get the coating off that we'll just see what it is. Just uh for interest one moment please. the transistor is out has been identified.

It is an SS eight, five five. Oh, and that is uh described as a PNP 25 volt 1.5 amp. The gain of roughly 200 and its application note suggests that it could be used and as part A push-pull arrangement for a 2 watt redial amplifier. and yeah, I find the Ss8550 In a lot of inverter designs, it just seems to be one of those things that it's found an alternative use.

but that is it. So if you need a battery operated uh, double Channel igniter where when you hold the button and it shunts uh, the contact The Greener yellow to the case uh, that is also used as the high voltage return, then it fires that particular circuit. see for instance, just a dual Uh gas burner stove or something like that with electric ignition with just a couple of Uh Double A's to run it. But that might be the perfect module for the job.

so that is an interesting circuit. Uses clever but slightly shitty I mean worms if you open this switch just as it Sparks well just as it well, just as it Sparks and also it would be dumping a lot of current through that switch at the time it could actually start finding a path back through a transistor. Quite strange, but I guess ultimately there must be a proven circuit so it must be okay, but that is another Uh electronic high voltage eBay special deciphered.