Hi friends,
I am trying to interface stepper motors with 8052. My stepper motors have come with drives which accepts 3 TTL signals viz. CLOCK, DIRECTION, START. I have to make start low to select the motor the direction defines the direction of rotation of motor and each osciallation of clocki causes motor to rotate through 1 half step. The motor has 200 full steps per revolutions i.e. 400 half steps. I am using following configuration on control board.
8051--->Optocouplers--->ULN2803--->motor drive
The problem is when I give clock pulses of 3KHz the corresponding output of ULN2803 oscillates at 3 KHz but rather than this being 5V peak to peak it is approx. 1V peak to peak. rather than giving oscialltions if i give a stedy signal it is approx. 5V when set high and approx 0V when low. I don't know why the output voltage drops at 3KHz. However the input going to ULN2803 from opto is nearly 5V P-P. I tried replacing the chip ULN2803 with another one but situation remains the same. I read the datasheet also but its silent on any such frequency issue Please give me some helpfull suggestions to sort out the problem.