Re: [CAD_CAM_EDM_DRO] Encoders for brushed servo motors

builder4wd wrote:

>I just bought two servo motors surplus, but they don't have encoders.
>I want to buy encoders to add to the motors, but I'm not sure what to
>look for. What parameters should I look at when shopping for these
>things? Thanks.
>
>

Well, you want sufficient resolution (counts/rev) such that you get the
desired position resolution
for the system. If you have accurate screws, you can preserve this
accuracy by connecting the
encoders directly (through helical-slit couplings) to the leadscrews,
and driving the screws
with belt drives. If the encoders are on the motor side of the belts,
small cyclical errors due
to belt pitch variations and sprocket runout can occur.

If you want highly repeatable home positions, you can use encoders with
an index channel,
and use this signal to refine the sensing of the home switch.

If your device that reads the encoder position can accomodate
differential signals, you will have
more noise immunity with a differential encoder.

For most purposes, you want encoders that produce digital quadrature
signals at "TTL" levels,
ie. 0 and +5 V, and run from a +5V power source.

Jon