Re: [CAD_CAM_EDM_DRO] encoder type?

jeff35m_73068 wrote:

>could someone explain to me the difference between; ttl,
>differential, and quadrature encoders.
>
>

All standard incremental encoders are quadrature. That means the
two channels (normally called A and B) have a 90 degree phase shift
between them. TTL means that a logic zero is roughly zero volts,
and a logic one is about 4 V. Differential means that each channel
(A and B) have two signals, and the logic state is determined by the
difference in the voltage between the two wires, not by an absolute
voltage level. This is done to compensate for electrical interference
on the encoder signals. You would then have wires marked A and A\
(A with a bar over it) and B and B\. You can just use A and B if
your device (such as a Gecko 320 drive) does not use differential
signals. If you have a serious interference problem, you could
put a differential receiver chip right at the input to the drive to
translate from differential to single-ended.

Note that many encoders are open-collector, maning they need a resistor
to +5 V to "pull up" the line when the driver is not forcing it to zero.

There are also special encoders made for use with interpolators that
provide an analog, sine-wave signal, either in the form of a voltage or
current. You'd generally want to avoid these.

Other types of encoders are absolute position, not incremental, and
may provide serial bit streams or a large number of separate signals
to identify position without any movement. Incremental enocders
only detect movement, and a count is kept from one position to the
next.

Jon