On Sun, 30 Jun 2002, Roman Black wrote:

>That's a brilliant idea, using hysteresis so that
>the negative pulse is detected too. Just keeping on
>with the "minimum parts" idea I wonder if this could
>be implemented by adding a capacitor to the single
>transistor circuit, so the + pulse charges it and
>the - pulse discharges it. This might give good
>fractional response but will probably generate the
>occasional false pulse as the cap discharges after
>the thing stops turning.
>-Roman

The minimum schmitt circuit using transistors, uses two of those. Barring
some funky-doped mosfets which nobody has off the shelf. The other parts
amount to too many so use the cheap opamps. Goldstar GL358 should be cheap
enough for anybody I think. Remember that you need a schmitt with high
sensitivity. Therefore you want opamps. 2 Transistor schmitts can achieve
50mV hysteresis and lower but they are harder to set up and use more
parts.

>Peter L. Peres wrote:
>>
>> Roman, I did not consider that you would have to resolve single detents.
>> You are right about there being one detent where there are two (-) pulses.
>> I propose the following two solutions:
>>
>> 1. Use a Schmitt trigger on each input. The Schmitts will 'integrate' the
>> pularised pulses and produce normal quardature outputs (sin,cos, indigital

I meant polarised. My spell checker has been dead for weeks now. I guess
it shows ...

Peter

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