TMC 188/40 Motion Control Module
TMC 188/40 Wiring Diagrams
Delta Computer Systems, Inc. 360/254-8688
103
Example Using 20mA Servo Valves with 25mA Output
5 0
C on fig ur e for
2 5 m A outp ut
2 5
5
V
out = 20 mA x (80 Ohms + 80 Ohms) = 3.2 volts across coils
R = 3.2 volts / 5 mA = 640 Ohms
You can use a this technique to scale the output current (100 mA, 50 mA, or 25 mA) to a lower full
scale current. This lets you use the maximum output resolution of the TMC 188/40 with valves
needing less than one of the full-scale outputs.
To find what wattage of resistor to use, calculate the power dissipation:
Power = I
2
x R
so:
Power = (5 mA)
2
x 640 Ohms = 0.016 Watts
A quarter Watt resistor would be a good choice.
