Ignition Coil High Voltage Display

Step 6: Results

The pictures below show the complete ignition coil system mounted on a board. The pulse generator circuit and IGBT switch are on a small custom PCB. The input power jacks, enable switch, and the on time and frequency controls are mounted on an aluminum angle bracket.

I'll repeat the safety warnings here. 

Excecise caution and good sense when working with high voltage. Remove power from the system before making adjustements.

Don't touch the arcs. Be mindful that the potentials generated can jump a significant gap, and that insulation on tools like regular pliers may be inadequate to prevent you from getting a shock.

Keep in mind that some parts of the system can get hot. The arcs can be hot enough to to ignite paper and plastic, so operate it in a safe location.

High voltage discharges generate Ozone gas, which can cause irritation if breathed in. High voltage discharges also generate some ultraviolet radiation, so limit your exposure and don't stare directly at the arcs.

The first picture is a short time exposure showing the arcs from the high voltage output when used with a power supply of 14 volts. Note that they arcs are distinct blue streams, as opposed to hotter arcs.

The arcs become much hotter when a greater power supply voltage is used along with a higher driver frequency. The subsequent pictures show operation using higher power supply voltages. Notice that the arc is now a hot and yellow.

The video shows how the output arcs are affected by changes to the repetition frequency, switch on time, and power supply voltage.

Comments

[tunes]

I have built one of these using the 555 timer and I now see that a PIC based design allows a greater degree of fine tuning to get to the resonant frequency of the coil. This seems important as different ingnition coils have slightly different capabilities in their output with the same circuit and voltage parameters. Some have used two coils in parallel/antiparallel to achieve even higher output voltages and longer arcs.

I would love to try your PC based circuit but I currently have no way of programming a PIC and have only Macintosh laptops at my disposal. I suppose I could invest in a PIC programmer and borrow a PC to just load the files on to the PIC. There are other projects such as the Aurora 9x18 RGB LED art (PIC24F08KA101) that also use a PIC from Microchip. Could I just buy the Microchip's PICkit 3 In-Circuit Debugger/Programmer? Would this work with the files you provide here?? Or could you sell me a few programmed PICs? I could also buy a few PICs and fedex to you for programming, if you would be willing to help me.

Also, could you send me a BOM for the parts list?

OK to email direct: [e-mail]

[trn2la]

Your comment got me thinking about something unrelated to the jaccob's ladder, but directly back to automotive applications. Many car modders are trying to extract every last little bit of power from their cars. One common way is with better ignition. Perhaps if coils such as these operate best at their resonant freq and that they all have a unique freq, then it may be beneficial for car enthusiasts to get their coil "tuned" to their optimal resonant freq. Perhaps with a little mass produced 555 IC based circuit built by you. I dunno, but there could be some dollars in a cheap little black box that goes between you coil(s) and power supply, with a potentiometer or something for tuning to the coils best resonance.Im sure you could elaborate further on that idea. Perhaps something is already available, but need simplification Comments :D

[LargeMouthBass]

Actually, ignition coils don't depend on resonance to generate the HV output.
There is a misconception among some that an ignition coil operates like a Tesla coil. An igntion coil is actually an iron core transformer, with a turns ratio on the order of 75:1. Switching off the primary current causes the primary voltage to rise to several hundred volts, which is in turn stepped up by the turns ratio.

What is important is to have an idea of the inductance and the resistance of the primary, as that lets you determine the time constant. From there you can configure your pulse generator to turn the switch on for an appropriate length of time.

I'm not familiar with the PICkit 3 In-Circuit Debugger/Programmer. If it is a product made by Microchip for general in circuit programming then it should be able to be used. I have actually never programmed any parts using in circuit programming before, but I know that there is an app note on Microchips web site explaining what you need to do regarding connections to the processor.

The files I have attached should work regardless of the programmer you are using. You will have to use the 12F683 with the files supplied, unless you know how to update the source code for a different PIC and then assemble to get a hex file for programming the different PIC. That isn't terribly difficult if you know a bit about the assembly language.

I don't have a BOM of the circuit per se, but the schematic has manufacturers PNs for all the more critical parts, like the processor and the IGBT. The other stuff is just common resistors and caps. 1/4 Watt resistors work fine. The caps you select must be rated to handle whatever maximum voltage you plan on applying to them. For example, the ones on the input to the +5V regulator will see the power supply voltage, so select them depending on the max power supply voltage you intend to use.

[tunes]

Thanks so much for your comments and the files.

Dan

[skowerr]

What would happen if I would connect a power audio amplifier (12V max) instead of the pulse generator... would I get a singing arch??

[LargeMouthBass]

This type of setup won't really work for the "plasma speaker" type projects. Those use a much higher drive frequency than can be used with an igniton coil. The drive frequency is usually tens of kilohertz, and then the audio waveform is used to alter the pulse width to modulate the arc to produce the sound.

The primary of an ignition coil has a fairly high inductance, and so the current can't be driven with a high enough "carrier frequency" which could then be modulated to produce any kind of reasonable quality audio. Flyback transformers are usually what is used for plasma speakers.

At any rate, the drive to the switch needs to be a digital signal to turn the switch either on or off, and so you wouldn't want to apply an analog signal directly to the gate/base of the switch you are using.

[skowerr]

Thank you for your comprehensive answer :)
I asked because it is easier for me to get for free a ignition coil than a flyback.
One more question. What type of material should be used for the electrodes, so they would not melt after a couple of minutes of arc production?

[LargeMouthBass]

The electrodes in this project are just 14 ga copper wire. I had no issues of the metal melting, but the insulation near the ends started to burn after a while. Brass brazing rods work well, and that is what I used on my Jacobs ladder that was built using a neon sign transformer. The brass can be somewhat better than copper in that it is stiff and so it will keep its shape better. But the copper works fine, just strip off all the insulation off to be safe.
The wires may get a little warm after producing arcs continously for a while.

I've only run the setup here for about 3 minutes at a time. If you are planning on making something to run for much longer, its best to check it out and see just how hot it gets. An of course, don't leave it unattended.

[RickO5]

Fun idea, I may have to try that.