control unit driver

hi

i am tring to drive a stepper motor STH-39D. i am getting the control signals from a FPGA Controller. the voltage levels of high and low signals of my control output are 4.4v and 1.37volts. i am using the following circuit as driver. i am using BC547 trasnsistors. the motor is not rotating. what might be the possible cause.
i think this is because of that the transistor is remaining ON even on "0" position. what changes in circuit should i make for this motor to keep running.
by the way forgot, my stepper motor is 1.8 step angle, 13ohm, resistance, 6 wired motor.

The 100ma BC547 is no match for your stepper motor. You've also left out the clamp diodes.
A ULN2803 would be much easier if your stepper is under 500ma.

I have used ULN 2803. but i am not getting the output. i have used the following schematic and i am posting my circuit.
My input pulse voltage varied between 0 and 3.3v for a 'BIT 0' and 'BIT 1' respectively. But the voltage on the output of the uln2803 is 0.59v costant value.
the schematic is given for 24v. but i have used it for 12v. id it causing the problem.?

Some data of the stepper motor would be helpfulf. The type number doesn't tell me anything.

The motor should have a label with the voltage and current printed on it.

I must assume that the motor is a 24V type. Driving it at half of the nominal voltage it won't work properly.

Boncuk said:

Some data of the stepper motor would be helpfulf. The type number doesn't tell me anything.

The motor should have a label with the voltage and current printed on it.

I must assume that the motor is a 24V type. Driving it at half of the nominal voltage it won't work properly.

Click to expand...

Independent of the motor type i should get some output from ULN2803. but the voltage at those terminals is just 0.59v what ever the input. i cant make out much on voltage of motor from that label on it as that label is damaged. it is a 6 wire , 13ohms, 1.8 step angle motor