This is a high voltage demonstration using an inexpensive car ignition coil being driven by a variable frequency, duty cycle and amplitude 555 based mosfet circuit.
Circuit schematic:
Very nice, but I've never had much luck having such drivers using the
555 survive for very long. The 555 usually manages getting destroyed in short order.
Well, I have about two hours of runtime on that circuit now so far. During the breadboarding phase, I did destroy a couple of 555 ics; but I'm pretty sure a voltage spike and/or esd from being too close to the coil and/or demo area is what caused it. And well, my breadboards were never intended for something like that to be running on them, so it's also possible one or more rails arced over on me on the breadboard and that's how I toasted the ic.
I added additional spike reduction circuitry when I placed it on the pcb, just in case. As a time saving precaution though, On the pcb, the 555 is socketed so I can do a quick change out in the event I do toast one. :)
I'm fairly confident that my circuit could run for hours, nonstop with proper cooling in place, but I seriously doubt the coil would actually tolerate it for that long without a break. My driver is pushing that coil way beyond what any car would ever ask of it. The driver circuit I built isn't limited to driving a car ignition coil either. AFAIK, It should be able to drive nearly any type of transformer out there; it has a large frequency range you can choose from and you can always increase it upto the max the 555 can handle; which is around 2.4mhz or so.
The
I know. It's one of the standards folks use for variable frequency drivers. I never went so far as to include a 555, but used to quite comfortably run a fixed frequency dual 2N3055 driven flyback. Even with a tripler, it could still supply mA's of current if necessary. The '3055's had to be on a fairly hefty heatsink, however and would get quite warm.
It can be a lot of fun to experiment with various drivers and HV coils. I always wanted to try one of the highest power mosfet designs, but lost interest a few years back. I see people getting 6" sparks with their ignition coils in oil driven by dual mosfet drivers. That's *really* pushing a coil, even in oil though!
:) There's a reason my circuit has the mosfet attached to that large heatsink; which I robbed from a 'dead' PS for a computer. (bad capacitors, but it made more sense to me to rogue it for the good parts; great desoldering practice and a variety of useful components). It'll get quite warm after a short period of time. The
3amp diode gets quite hot after a short period of time too. My circuit is by no means perfect, I still consider it to be prototype level.It's not the mosfets so much as the voltage they are feeding the coils; along with reverse phasing and letting the coils arc to each other. I've seen more than one case where that goes wrong, arc over occurs and something gets toasted. :( It's difficult to provide enough insulation the higher and higher you go. The more kv you opt to get, the greater it can travel through the air and your insulation materials to a source of ground you might not have even known about; until you see it arc. [g]
I've seen some flybacks explode too, and well, to me, that's really dangerous if you happen to be near it should it happen. I know, sounds crazy, HV doesn't bother me, but... resulting explosions do. [g]
Incidently, I had a 555 die a horrible death the other day. A chunk is missing from it; you can see what's left of the circuitry in the bottom of the crater. I'm pretty sure the fets blown too; and I strongly suspect a short circuit has occured someplace; perhaps in my TIP47c.. I uhh, performed an experiment using the wrong type of capacitor and while it did seem to work quite nicely for a few seconds, that's as long as it did so. lol. Oh, capacitance can be such a f****ng bitch...
Granted, that particular 555 wasn't a TI, but an el cheapo (I paid mebbe 3 dollars us for 30 of them, shipped to me) model. I might actually leave them a semi bad review.. There chips smoke, blow up, etc. The TIs if I kill one just basically, die. No smoke, no explosion, just ... dead.
Try the same circuit - with the same bad cap - with a TI - bet it does the same. I've had them totally fracture - nothing but 8 pins and fragments of burned phenolic or ceramic or whatever the"chip" is made of and a cloud of stinky smoke, with a crater in the PC board.
Took some stupidity on my part but it sounds like you are not totally ruling out that factor in yhour case either!!!!
Clare Snyder snipped-for-privacy@snyder.on.ca>
news: snipped-for-privacy@4ax.com Sat, 09 Nov 2019
21:15:55 GMT > > [snip]
I finally had time to confirm my suspicion (for my own circuit anyway). It literally smoked or caused the non TI triple 5s to blow chunks out of themselves. I've since modded my circuit a little more and now, it's not blowing the offbrand or the TI ones. Or the fets, or anything else.
Incidently, My Darlington has managed not to get taken out, even though both components tied into it have been killed horribly more than once. <G>
Oh certainly not. I've been working on this circuit off and on for a good bit of time now as I could allocate the time; and not factoring in waiting on components and/or finding viable salvage boards which have a good chance of having the parts I'm wanting. <G>
I've made a bit of progress:
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