inverter + ignition coil = sparks

Title says it. Works with a square wave inverter and power limited 12V supply and a suitable capacitor in series with the coil.

Category:

Howto & Style

Tags:

• inverter
• ignition
• coil
• spark
• high
• voltage

[hscess]

Ok, now we are getting somewhere. It looks like I can use a AC motor start capacitor with at least 400 AC volts along with my automotive coil and get some really nice arcs. Is this right? Feed my PWM 12 volts----use a 400volt AC start capacitor---and an ignition coil----sparks.

[decod31]

@hscess I don't know what your PWM outputs so impossible to know. If the output is only 12V then it'll never work well due to the internal resistance of the coil. The sparks occur when there is a fast 400V transient in the coil input. The purpose of the capacitor is just to limit long term current if the waveform/voltage is not suitable. The other way is to operate it is a flyback mode, then the sparks form when large current is suddenly switched off giving a large inductive voltage spike.

[decod31]

@hscess There is a link to coil guide I wrote a while ago in my video 100kV.... I-coils are transformers with ~1:100 ratio. So you need to hit it with 400V to get to 40kV. There are two ways to do it. First is to actually use ~400V, the other is to make a current, say 10A to flow through it (limited by internal resistance, 24V with optimized waveform works) and at maximum, quickly switch it off. This will give a voltage pulse due to inductive kick reaching 400V at the in and 40kV at the out.

[hscess]

If understood you right. !2vdc input to the PWM and output is AC, or am I not looking at this right. I know that the PWM chopps the 12vdc to controll motor speeds. I have tried to use dc capacitors and failed. The only one I can make work is the condensor/capcaitor that cam from a points type distributor.

[decod31]

@hscess The makes around 230VAC 50 Hz (EU-model) from 12VDC. The waveform is "modified sine wave" which is a kind of square wave with peak amplitude of 325V, but duty cycle giving around 230V average. The capacitor needs to be able to handle at least the peak voltage. I don't exactly know what you mean by dc cap, you should never use a cap with polarity with AC. Electrolytics are "DC", most others are bipolar and usable. Cap needs to be right and the 12V supply needs to be able to give ~1A.

[hscess]

Did you use vdc capacitor ? If so what size?

[decod31]

@hscess Hmm, only vdc I know refers to the max volts of DC. I used a 0.47uF 1000V or so polyester capacitor which naturally isn't unipolar and never should be unipolar in this application since the inverter gives out AC. The purpose of the capacitor is to limit the short circuit current and allow the inverter to keep operating. Wrong value might break the inverter. Not power limiting the supply might also break the inverter.

[hscess]

Did you use vdc capicitor? If so what size?

[eric018]

hey how can i test a twin ignition coil for 13b rotary engine?? it has a lot of wire... help please..

[decod31]

I believe it would be more accurate to say that you had your biasing of the transistor wrong way because switching polarity doesn't affect the coil, but cool anyways. Yes, IGBTs are great, quite similar to mosfets in this application though. IGBTs really stand out with tesla coils due to their high current handling.