I was wondering if someone could help me out. I run an efan. I'm about to install a Summit Racing 850611 digital ignition box. While reading reviews of the unit I found mention on a forum that with efans I would need to install diodes in the system or risk frying the micro processor.

Does anyone have experience with this? Which diodes, placed where?

Thanks for any help.

 

Diodes are frequently used to prevent back EMF from damaging the output device whether it's a relay or MOSFET. When an inductive load is switched on, a magnetic field is generated within the device. When power is removed, that field collapses. Whenever you have a conductor and a magnetic field in relative motion, you get a voltage. The result in this case is a rather high voltage spike in the reverse direction. This can be enough to take out a transistor or burn the contacts on a relay. The diode gives this voltage a low resistance path that keeps the high voltage from reaching the output.


This image is from pcbheaven.com. It shows where the diode goes and give some of the names you'll find it under.





I wonder why the ignition box is concerned with the fan. Is it driving the fan? Or are the forums saying that a electric fan in general will affect the box?


Michael

 

The ignition box should have a diode as part of its circuitry anyway, they often do as they contain sensitive electronics.

I would not worry too much about this, just make sure you have the appropriate relay for the electric fan (generally 30A is fine) and you will be okay. I would also recommend a temperature sensitive actuator to keep the wiring tidy and stop you from having to remember to turn the fan on. They can be had cheaply on eBay for $20 or less.

- boingk