Re: encoder identification and specs

--- In CAD_CAM_EDM_DRO@y..., Denis Casserly <denisc@a...> wrote:

> Hello,
> I have 3 brush type servo motors with encoders and am trying to

locate the

> specs on the encoders.

David: The chances of finding a schematic are pretty slim. The part
number could well be the vendor's part number for that PC board. If
you have access to a power supply and scope you can try the following:

Open the unit and see if you can identify the Power and Ground pins.
Clues are an electrolytic cap with the - lead connected to a run.
IT's probably ground. The IC's often have pin 7 (on a 14 din DIP)
connected to ground but not always. Most board designers make their
ground runs larger and often layout larger areas of copper to form a
ground plane. If you have the connected wires a popular color for
ground is black. Red is often used for +. Once you establish power
and ground clip on a current limited supply with the current limiting
turned down to 250ma and apply 5 volts of power. High currents would
indicate the connections are wrong.

If all seems well quickly run you finger over the IC's and other
components and feel for hot spots. Ground your scope probe ground
lead to the negative side of the power supply and with the unit
powered up pick one of the other leads to monitor. Turn the shaft
and watch the scope. If you get pulses that are 0 to 5 volts then
you have one of the channel leads (maybe). If you don't get pulses
then it try the other leads. If still no pulses then you may have a
differential output unit. Try moving the scope ground to one of the
other pins and once again test alll other pins for pulses as you spin
the encoder. Keep trying all the combinations except putting the
scope ground on the positive lead of the power supply. If you get
pulses indentfy the pair that give you pulses.

Hopefully by this point you have found your pins. If you have not
there are two remaining possibilies: The unit is designed to work on
higher voltage (12, 15 or 24VDC) or the outputs are open collector
and need pullups.

You might get lucky and someone on the list knows what the pins are
but usually I have to perform the above "easter egg hunt" to figure
things out. Hope this helps.