Opto 1-Max Practical Tooth Count

[wes kiser]

I am interested in using the Opto 1 circuit for a toothed wheel. I understand the VR sensor is recommended for high tooth count wheels.

I am planning a 12-1 wheel on the crankshaft, and a maximum engine speed of 8,500 rpm. Is it feasible to use the opto 1 circuit for this? I assume frequency/cycles is what we are concerned with? I am making the wheel, so I can go lower if required.

[Bruce Bowling]

Wes - there is some filtering on the Opto side that may phase shift high tooth count. There is that 0.2uf cap in the circuit that provides a lot of filtering for ignition coil ringing, but can cause delay for high tooth count/high RPMs.

Is this for Microsquirt module? If so then you may be OK, the large 0.2uf cap is not populated on the module. Best thing to check would be to scope the input and the output of the opto circuit (where it goes into the processor) to see if there is measurable phase shift.

- Bruce

[Martin Wagner]

Wes - there is some filtering on the Opto side that may phase shift high tooth count. There is that 0.2uf cap in the circuit that provides a lot of filtering for ignition coil ringing, but can cause delay for high tooth count/high RPMs.

Is this for Microsquirt module? If so then you may be OK, the large 0.2uf cap is not populated on the module. Best thing to check would be to scope the input and the output of the opto circuit (where it goes into the processor) to see if there is measurable phase shift.

- Bruce

If I remove the c27 (Dave) cap and maybe the c28 (Ed) cap would the opto work with a 36-1 wheel at 8500 rpm? We have had a lot of trouble with the vr sensor or sensor connector that we have been using and would like to find something more reliable. I thought a hall sensor (Honeywell 1GT) through the opto side might be more reliable.

Marty

[wes kiser]

Yes bruce, this is for a microsquirt module. I am making the wheel, so choosing something relatively low (I picked 12-1 because it is double the cylinder count) is not an issue.