Ignition coil driver

[SJP6]

Hello!
over the past few weeks i have been interested in what you can do with high voltage power.
Ive been looking at things like tesla coils, but have so far been held up at the stage of how i will convert my low voltage to high voltage. i have read that neon sign transformers are the best option...but im not too keen to run such a thing off mains power. SO instead i have been looking at using an ignition coil.
But in terms of actually finding out exactly what i need to do to build a driver for an ignition coil, is where i am at a stand still.

I have found some stuff on the internet but its all been quite confusing to me, as i am by no means a wiz with electronics (but by the same token, am not new to it either).

from what i know so far, i need to pulse direct current at the two terminals on the ignition coil, to achive a high voltage from the output on the coil.
I am lead to believe that this is done by using a PWM, but is this as simple as taking a PWM for dc motor speed control and attaching the output wires to the coil? and what frequency will the PWM need to achive?

Kindest regards,

SJP6.

 

[Sceadwian]

Try a CFL inverter, cheap, goes up to 2-300 volts peaks, readily available. If you need DC high voltage rectifier diodes is all you need.

 

[SJP6]

was looking at something to produce around 4,000 volts. (at like 30ma)
from what ive read im pretty sure you seed something in the thousands to make goof arcs and plasma.

 

[Boncuk]

An ignition coil supplies between 15 and 25KV (high power ignition coils do 40KV) connected to 12V on the primary winding.

I recommend to use a maximum frequency of 150 to 300Hz at 30 to 40% duty cycle.

At higher frequencies and higher duty cycles the coil might overheat.

You won't probably get an arc, but nice sparks.

 

[SJP6]

Thanks!

So if i were to buy one of these:
**broken link removed**

would this run the coil to produce a decent voltage?
and would i need to take any measures to protect my circuit from frying?
because i had a similar set up once before and the transistor overheated...

 

[rogsilk]

You could use this project as your frequency provider (RMCybernetics - DIY Homemade Power Pulse Controller)

 

[shortbus=]

Rogsilk beat me to it; **broken link removed**

Alot of good stuff there.

 

[stevez]

Just a brief comment: Capacitive Discharge and other "electronic" ingition systems were part of the transistion away from the old points-condenser approach. These systems drove standard or common ignition coils and researching this might provide some useful circuits or ideas.

 

[crutschow]

An ignition coil supplies between 15 and 25KV (high power ignition coils do 40KV) connected to 12V on the primary winding.

I recommend to use a maximum frequency of 150 to 300Hz at 30 to 40% duty cycle.

A standard ignition coil has a turns ratio of about 100:1 so applying a 12V pulse to the primary will only generate 1200V on the secondary. You need 150-250V on the primary to generate 15-25KV on the secondary which can be provided by inductive kick as in a Kettering ignition (run several amps DC through the primary and then suddenly interrupt the current) or apply the 150-250V to the primary from a charged capacitor as a CD ignition does.

 

[Boncuk]

A standard ignition coil has a turns ratio of about 100:1 so applying a 12V pulse to the primary will only generate 1200V on the secondary. You need 150-250V on the primary to generate 15-25KV on the secondary which can be provided by inductive kick as in a Kettering ignition (run several amps DC through the primary and then suddenly interrupt the current) or apply the 150-250V to the primary from a charged capacitor as a CD ignition does.

Ignition coils do not ignite the air-fuel mixture when activated, but when deactivated. (That's why the closing anlge is less than the opening angle. E.g. 11deg closing and 79deg opening angle with the Renault R30 - 6 cyl. engine.)

An engine won't ignite at full combustion pressure of 12 to 15 bar (~360 to 450psi) and an ignition voltage for the spark plug of 1,200V.

You can observe the spark in a car repair shop where they have a spark plug tester. The test chamber is pressurized to the the combustion value. At atmospheric pressure a faulty spark plug seems OK, but it won't spark with pressure applied.

Even magnetic ignition systems, used for aircraft engines use the collapsing magnetic field to generate high ignition voltage.

The back EMF voltage is much higher than that calculated from the turns ratio.

I had severe trouble with a 24VDC solenoid killing transistors and burning out protective diodes. Measurements proved that the back EMF was about 170V.
A fast recovery diode rated 700V solved the problem.

Boncuk