122 • Chapter 7 Application Programming DMC-2X00
PR,,80000 Raise C
BGC
AMC
VP -37600,-16000 Return AB to start
VE
VS 200000
BGS
AMS
EN
R=2
B C
A
0 4 9.3
4
B
A
Figure 7.2 - Motor Velocity and the Associated Input/Output signals

Speed Control by Joystick

The speed of a motor is controlled by a joystick. The joystick produces a signal in the range between -
10V and +10V. The objective is to drive the motor at a speed proportional to the input voltage.
Assume that a full voltage of 10 volts must produce a motor speed of 3000 rpm with an encoder
resolution of 1000 lines or 4000 count/rev. This speed equals:
3000 rpm = 50 rev/sec = 200000 count/sec
The program reads the input voltage periodically and assigns its value to the variable vin. To get a
speed of 200,000 ct/sec for 10 volts, we select the speed as