Re: [CAD_CAM_EDM_DRO] Encoders

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.

if you still have the rest of the plotter, you may be able to get more
info from looking at that, too. But, if you know the +5 and gnd. then you
can power the encoder and use a meter to figure out what the other
signals are. it may have the A and B quadrature channels and an index
channel that was unused by the plotter.

You can count the cycles of the encoder with a meter that beeps.
If you get 50 beeps in one revolution, then that encoder would count 400
quadrature transitions per rev.

Jon