> I am working with an optical encoder which outputs a voltage
> between +0.35VDC and +1VDC. What is the easiest low
> component count method for getting a clean 0V to 5V pulse
> from this to use as an input to the PIC?

If those voltages are reliable levels then a transistor will work well with
3 resistors.

If they aren't reliable then a bit of design will still produce the goods.
Ask with more details if this is the case.

A 555 as suggested MAY work but needs design.

TRANSISTOR. DESIGN

    Cheap. Easy. Compact. Learn something. Works.

NPN small signal. Just about anything. (2N2222 or whatever)

R1 Input resistor 10k to 100K from input signal to base.
R2 Pulldown / leakage shunt 100k to 1 megohm base to ground.
R3 Collector resistor 10k to 100k collector to Vdd.
PIC pin to Vdd.

R2 can perhaps be omitted but its good to have it.

Cheap. Simple. Works if voltages are as stated.

R1 larger makes less load on signal
R2 at least 10 x R1 (more OK)
R3 could be 1M probably but 100K OK.

If this signal is very high speed things will get more complex. The above
should probably work at eg 10 kbps without a thought.
Maybe at 100 kbps
Almost certainly not at 1 Mbps



        Russell McMahon

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