MicroSquirt: drive a PWM idle valve directly

tineira · Post by **tineira** » Tue Dec 25, 2007 7:05 am

Can the IPS022G that controls the FIDLE on the MicroSquirt drive a PWM idle valve directly, or do I need to make an external board using a TIP122 or something similar.

Its a 3 wire Toyota 4AGE silvertop idle valve, it has 2 coils, one to open the valve, and another to close the valve. Each coil has between 17 and 28 Ohm according to the manual. I plan to ground the wire that goes to the coil that closes the valve, and connect FIDLE to the other coil.

Matt Cramer · Post by **Matt Cramer** » Thu Dec 27, 2007 12:26 pm

Yes, you can. From the wiring section of the manual:

This is the output for controlling an ON/OFF style FIdle or a PWM style IAC.

tineira · Post by **tineira** » Thu Dec 27, 2007 12:41 pm

Thanks!

Glen Hoag · Post by **Glen Hoag** » Thu Dec 27, 2007 1:59 pm

However, it's only a single output, so you can't drive a Bosch or Denso three wire rotary solenoid valve without resorting to the "resistor on the closing coil" hack originally developed for MS1/Extra, or an external solution consisting of an inverting stage plus a high current driver for the other coil.

I have a board for MegaSquirt that implements this, but it would be difficult to put it into the MicroSquirt case. You would only need one high current driver, so this board is a bit of overkill.

It should be possible to repurpose one of the LED output drivers to be the inverse of the FIDLE output, but that would take a code change. The LED drivers use the same circuit as the FIDLE and fuel pump drivers, so they will handle the current.

--Glen