turn off. The voltmeter should read +5VDC. Turn the motor shaft clockwise VERY slowly. The voltmeter reading should 
decrease 0.04 volts for every encoder count. When the reading reaches 0.4 volts, the red light will turn on and the voltage 
will jump back to +5VDC. After 3 seconds the light will turn off. You may turn the motor shaft counter-clockwise as well. 
The voltage will increase then by 0.04 volts per count until it reaches 9.6 volts and trips the protection circuit. 

OSCILLOSCPE MONITORING: Set the scope to 2 volts / cm vertical and about 1 millisec per cm horizontal. Zero the 
trace to the bottom line on the screen. DC couple the input. Place the probe on the test point and the ground clip to the 
blue capacitor ground lead. Follow the steps in VOLTMETER TESTING above. 




STEP 4: CONTROL INPUT HOOK-UP

The control input group is the standard step motor drive STEP, DIRECTION and +5VDC lines. The STEP and 
DIRECTION signal drivers must be TTL compatible and have edge transition times of 100 ns or faster. The +5VDC is the 
opto-isolator common anode line and must be returned to the pulse source +5VDC supply. 

(TERM. 10) DIR Connect the DIRECTION line to this terminal. 
(TERM. 11) STEP Connect the STEP line to this terminal. 
(TERM. 12) +5VDC Connect this terminal to the controller +5VDC power supply 

STEP 5: TESTING THE CONTROL INPUTS

You may wish to test the functionality of these inputs. If you used an oscilloscope in the previous section, leave it 
connected to the test point. If you used a voltmeter, then remove it from the drive. 

Set the STEP pulse generator to about 40 pulses per second and set the DIRECTION output to clockwise (logical “1”). 
Turn on the power supply. After the power-on reset period of 5 seconds the FAULT light will turn off. 

If you are using an oscilloscope, then the test point voltage will begin to increase until 3 seconds later it trips the protect
circuit at 9.6 volts. The FAULT light will turn on for 5 seconds and voltage will snap back to +5VDC. After the FAULT turns 
off, the sequence will repeat again. 

If you are not using an oscilloscope, just see if the FAULT light turns on and off every three seconds. 

STEP 6: MOTOR HOOK-UP

Make sure the power is off and the STEP pulse source is set to zero pulses per second. Check to see if the trimpot 
settings are set according to the instructions on page 2. You may wish to secure the motor so it can’t jump off the bench. 

(TERM. 3) ARM- Connect the RED motor lead to this terminal. 
(TERM. 4) ARM+ Connect the BLACK motor lead to this terminal. 

STEP 7: TUNING THE SERVO 

Turn on the power supply. The FAULT light should turn off after 3 seconds. If everything is correct you should hear the 
motor “singing”. This is normal. The motor is dithering or bouncing between adjacent encoder counts. The integral term in 
a PID loop has infinite DC gain over time and will amplify even the smallest position error. Because encoder feedback can 
only occur on count edges, the loop is “blind” until it encounters an encoder count edge. It then reverses the motor 
direction until another edge is found, then the process repeats.