Re: Linear Encoder Question

TADGUNINC@... wrote:

> The piece I was inquiring about is shaped like an "F" with a single slot in
> the opposing faces of the legs has a drawing of a diode on one of the legs.
> I think I can figure out, with a diode tester, which pins are for the led?

If it has a photodiode as the sensor, they may look very similar on a
diode tester. But, probably, the sensor will be more sensitive to room
light.

> do
> you think it would work off of VCC or a smaller voltage?

You will have to put a resistor in series with the LED to limit current.
You probably want about 20 mA through the LED.

> And finally, am not
> familiar with these types of devices, would you use the output to drive a FET
> or transistor to gain some useful current capabilities or would you be able
> to hook it directly to one of the limit/home circuits of one of the
> driver/controllers?

You very well might be able to drive a CMOS input directly from a photodiode.
You definitely can from a phototransistor. In either case, unless the device
receiving the signal already has a pullup resistor to +5 Volts, you will need
to supply one. It will take some trial and error to get the right pullup value.
You want one such that when light crosses the gap the output goes close
to zero volts, but when the slot is blocked the voltage is at least +4 Volts.
10 K Ohms might be a good place to start.

If the sensor is very weak, then you might need an amplifying transistor, but
this sort of sensor should not need it.

Jon