Hello everyone. I am trying to build a circuit in order to drive a unipolar stepper motor that I have. The circuit I am building is shown below. Ok I understand that the upper diodes are to protect the MOSFETs from back EMFs, but what are the lower ones for? I asked a lab supervisor at the university and he told me to get fast diodes for the upper four diodes and schottky ones for the lower four diodes. The lower ones do not have to have current capabilities as large as the upper ones. The motor windings are rated at 2 amps so I got 4 diodes with 3.5 amps current ratings. The forward recovery time of the diode is 210 ns and the reverse recovery time is 50 ns. Is this considered fast enough?! This is the fastest diode that I found that has the required current ratings.
The MOSFET I got is the IRF530 and the schottky diodes are of the type 1N5818. Please tell me if this is a good design.
I also have a final question please. The rated voltage of the motor is 3 Volts. However, I only have one power supply at the moment and I need to operate the motor from a PIC (5 Volts). Normally, I set the supply at around 9 volts and use a regulator to get a steady 5 volts to power up my breadboard. What should I do now? Should I use a potentiometer to get the 3 volts for the motor?! I know this is bad design but until I get another supply, what can I do?
Thanks a lot.
Nichola V. Abdo
The MOSFET I got is the IRF530 and the schottky diodes are of the type 1N5818. Please tell me if this is a good design.
I also have a final question please. The rated voltage of the motor is 3 Volts. However, I only have one power supply at the moment and I need to operate the motor from a PIC (5 Volts). Normally, I set the supply at around 9 volts and use a regulator to get a steady 5 volts to power up my breadboard. What should I do now? Should I use a potentiometer to get the 3 volts for the motor?! I know this is bad design but until I get another supply, what can I do?
Thanks a lot.
Nichola V. Abdo