I am constructing an electronic ignition system for model engines.
Update january 25 2005, click
Run from a 4,8, 600 mAh battery
Use CDI to get a hot spark, even when starting.
Minimal part count
Ignition on/off by RC control
The ignition will be based on a free running oscillator to generate the CDI
voltage, a SCR to control the fiering, and a PIC chip to control the advance. A
standard Modelectric coil is used. A hall effect IC reads engine position.
September 26 2003
First prototype built, crude construction, but it works.
1 Transistor BD242B
1 Thyristor 2N6237
4 Diodes 1N4001
1 Resistor 500 ohm
2 Capasitors 4,7nF and 0,47uF/250V
1 homemade toroid coil, see belov
1 Modelectric coil
||Waveform from prototype:
Upper track is the trigger pulses
Lover track is the CDI voltage
Works wery well.
Strong spark, even at 500 Hz (30000 RPM)
The ferrite core is a very common type; it is taken from an old computer. It was
used as an RFI suppressor on the motherboard cables.
It has an outer diameter of 2,5 cm.
The 3 windings is made like this;
L1 20 turns of 0,5 mm
L2 10 turns of 0,1 mm
L3 450 turns of 0,1 mm
All windings must go in the same direction, and must not be too loose on the
Wind L3 first.
When done, put on some lacquer to fix them.
The components values are form my prototype, but none of them is critical, use
what you have…
To trigger the unit, use a Hall Effect device with logic level output.
Mount a small magnet on the flywheel, and position the Hall Effect device so the
magnet will trigger it.
The next step is to make the advance control. I will use a PIC
microcontroller for this, probably a PIC12C508/509.
Fell free to send send me a mail, if
you have any questions.