Differences between microsquirt and standard 3.0 VR circuit

[wes kiser]

I am attempting to implement a hamlin 55075 Hall effect geartooth sensor. It ouputs a square wave equalling the input voltage, and varies from 0v to input voltage. I like the idea of using this sensor because of issues people seam to have with the VR sensors, and it has a threaded body (meaning gap is very easy to set). It is also around 20$.

A while back I attempted to use it with the standard v3.0 input circuit, with the zero crossing adjusted. It worked great, but would not read past 4900 rpm with a 36 toothed wheel. The frequency response of the sensor is 15khtz, which should 25k rpm on a 36 toothed wheel.

I asked some one to try it on the microsquirt, but hooked to the vr circuit with the "offseter" circuit, and with a 36 toothed wheel it worked well up until the bikes rev limit (8500 rpm). This would indicate the issue is with the v3.0 conditioning circuit and not the sensor. What is different that would affect the response of the circuit?

I realize I could likely just use the standard optical input, but I really like the idea of using the vr circuit as a "one size fits all" application. I thought asking the question here makes sense, because I know the microsquirt input circuit works.

[sportage4x4]

i'm curious as to why you would use hall sensor on the V3 board through the VR input circuitry? why not just connect it to the hall/opto input?

[Bruce Bowling]

The circuits b/w the V3 board and Microsquirt are practically the same, at least electrically. Now, on early V3 boards the input capacitor was really big, like 0.1uf or thereabouts. This will kill the high-frequency response. Check to see that this cap on your board has been lowered to something like 0.01uf. You should be able to get the same operation on both.

- Bruce

[wes kiser]

i'm curious as to why you would use hall sensor on the V3 board through the VR input circuitry? why not just connect it to the hall/opto input?

Generally, by the time an individual figures out their particular VR "system" (sensor, mounting, wiring, etc...) has problems, they have already installed the VR circuit. There was some interest a while back about making this circuit the "only" input circuit, as theoretically it is adjustable enough to work with most installs. I have not saw any progress on this lately.

Either way, if someone already has a running driving setup, and a hall sensor can be installed with not squirt modifications (except a few turns of some pots) this makes life easier in most instances I have encountered that I could not make the VR circuit play nice in a half hour.

Since I am now way off topic for a microsquirt forum, I will leave this alone. Thanks Bruce, I was aware of the caps, but did not know if the microsquirt was intentionally different in this respect.