Re: [CAD_CAM_EDM_DRO] Encoders

Hi Ian,

If you've got the power and ground figured out, Fire it up! Hang a
scope on each of the output lines, and watch for quadrature (square
waves)! I have also seen sine waves (OK, it was late at night) out of
some printer motor encoders. There are probably A+ and A- leads
(differential?) and B+ B- leads brought out, if you have that many
leads. You will therefore possibly see a square wave, and an inverted
version of it (hope you have a dual channel scope). You should also see
a "quadrature" relationship between appropriate output pins (90 deg
lead/lag).

Count the slots? Not me. I wrote some simple software to detect the
changes, and display a count on the screen. Then I make a pointer, put
it on the shaft, and make 10x revolutions, and observe the final count.
Try that a few times, and you'll have a pretty good idea of the
resolution (/10!).

Have fun!

Alan KM6VV


Ian Wright wrote:

>
> Hi,
>
> In a previous post I mentioned that I have acquired a couple of old
> plotters - well, one of them is now less than its previous self and the
> motors, controller etc., are sitting on the bench in front of me.
> The encoder bit of the motors has a 10-way ribbon cable coming from it and I
> have attempted to trace the wiring - not too successfully. There appear to
> be 4 black wires which are all connected together electrically (as far as I
> can see with my ohmmeter) which I presume are groungs, 3 red wires which are
> also electrically connected which I assume are +5v (I know these are
> connected to the LED which shines through the encoder disk via a 120 ohm
> resistor). There are also 3 other wires, brown, white and green which I
> assume are the outputs. On the small PC-board inside the encoder I can see
> through plated holes marked A+, A-, B+, B- but I can't trace where they are
> connected to as they dissapear under the encoder disk, they certainly aren't
> connected directly to any of the output wires.
> So, without having any 'serious' test equipment, is there any way I can
> determine what the various wires do and what the encoder count is (for
> preference without having to take the encoder disk off and count the lines
> by eye!) ? If it's any help, the colour sequence is:-
> brown, red, white, red, black,black,black,black,green, red.
> Thanks,
>
> Ian
> --
> Ian W. Wright
> Sheffield UK
> www.iw63.freeserve.co.uk