Download Application Note #1435 100

Application Note #1435
Protecting Encoder Input Circuitry
If there are voltage spikes which are damaging the line receiver inputs of the Galil
controller, the input circuit may be protected by placing 2 diodes on every encoder
input that is used on the controller (CHA, CHB, CHA-, CHB-).
The procedure and diagram for this modification are as follows.
1. Place one diode with the anode connected to the encoder signal and the cathode
connected to + 12V.
2. Place the second diode with the cathode connected to the encoder signal and the
anode connected to -12V. A resistor, such as 100 Ohms, should also be inserted into
each line prior to the diodes.
Generic electronics diode (such as 1n914 or 1n4148) should be sufficient. The diodes
will clamp the input and the 100 Ohm resistor should limit the current into the diodes
to keep them from being damaged.
+12V
From
Encoder
To
Controller
100
Diodes are
1N914 or
1N4148
-12V
-1Galil Motion Control, Inc. • 3750 Atherton Road • Rocklin, CA 95765 USA • 800-377-6329 • Ph: 916-626-0101 • Fax: 916-626-0102 • www.galilmc.com