logic level tach trigger inputs

For engine experimenters, the MicroSquirt® PCB is offered in a module format with enhanced capabilities to be plugged into other boards. This is the place to discuss the MicroSquirt Module.
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ChaosAD
MegaSquirt Newbie
Posts: 10
Joined: Tue Dec 21, 2004 9:48 pm

logic level tach trigger inputs

Post by ChaosAD »

What is the best way of using an external VR conditioner setup with the microsquirt?

The toyota 4age dizzy pickups can cause a lot of problems with tach resets and ive found a setup that works.
However the mdule doesnt have logic level inputs for the crank and cam pickups.

Will the microsquirt module VR circuits accept a 0-5v logic level input? or would I need to condition the signal to make it pass through 0v?
Bruce Bowling
Site Admin
Posts: 285
Joined: Mon Feb 16, 2004 4:25 pm
Location: Baltimore, MD

Re: logic level tach trigger inputs

Post by Bruce Bowling »

The CAM VR input (VRIN2) threshold is set to 1.7 volts, this will trigger fine with TTL logic signals.

The CRANK VR input (VRIN1) needs to go thru zero. What you need is the "VR Offsetter" circuit add-on, see:

http://www.microsquirt.com/viewtopic.php?f=87&t=22790

Just be sure to use an open-collector drive on the output of your circuit (like a hall output), if the drive signal is a totem-pole output the circuit will not work. Use a simple transistor to do this, and you can still drive the collector off of +12V if you want.

- Bruce
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