Hi all,
Does anyone have any experience connecting TTL level (unbalanced) quadrature encoders directly to the balanced encoder inputs of a Galil motion controller? Will it work?
I have two motors that have an unbalanced quadrature TTL output, and they are very close to the Galil controller, so I would not expect to have any noise issues if I ran them straight to the card. I was hoping to connect the galil A- and B- and I- inputs to ground.
If this wouldn't work, I could interface the TTL outputs with a AM26C31Q chip, which would convert them to balanced outputs, but I would not want to do this unless it was absolutely necessary.
Regards, Phil
Phil on 07/02/2016 - 01:13
OOps, I just read the manual and it says you can connect single ended 5V encoders directly. That's great news. In the manual it also says:
"Single-ended 12 Volt signals require a
bias voltage input to the complementary inputs"
Not sure why 5V single ended signals don't need a bias input but 12V signals do..... Can anyone clarify? This is a DMC 1880 controller.
Phil on 07/02/2016 - 01:18
Here is the full text in the manual. My main question now is whether a bias voltage is required using 5V TTL encoders:
Quadrature encoders may be either single-ended (CHA and CHB) or differential (CHA, CHA-, CHB, CHB-). The controller decodes either type
into quadrature states or four times the number of cycles. Encoders may also have a third channel (or index) for
synchronization.
The DMC-1700/1800 can also interface to encoders with pulse and direction signals. Refer to the “CE” command in
the command reference for details.
The standard encoder voltage level is TTL (0-5v), however, voltage levels up to 12 Volts are acceptable. (If using
differential signals, 12 Volts can be input directly to the DMC-1700/1800. Single-ended 12 Volt signals require a
bias voltage input to the complementary inputs).
Phil on 09/07/2016 - 23:37
After experimenting, I have found that using 5V unbalanced (TTL) level quadrature encoders works great, as long as the complementary pairs are not terminated.
Grounding the complementary pairs (at the Galil end) seems to cause problems.
KushalP on 01/26/2017 - 08:43
Hi Phil,
If you are connecting single ended encoders, you can connect them directly to the MA+ and MB+ inputs. You would not connect the MA- and MB- signals. You would also not tie these to ground. If however your controller has the termination resistor option (-TRES) installed then you must use a quadrature encoder, where MA+, MB+, MA-, and MB- are connected.