I’m trying to drive a DC motor from a shift register connected to a transistor array.
Here is my schematic,
The first shift register controls relays, and this works just fine, But when we try to control the DC motor from the 2nd shift register, It tries to move but then stop, So you can hear the motor make noise for a second then its done.
with a Volt meter on the out put of the first shift register it reads 3.3 v when the singal is high, and then the relay turns on. This is great !
But when we connect the volt meter to the 2nd shift registers output it Spikes from 0 -3.3 v then instantly back down to 0 or about .06v
Also we tested Powering the Transistor array with a +3v power to the input pin. This bypasses the shift register, and the motor turns just fine. So that leads me to believe that the transistor array is wired correctly.
When I plug the transistor array and motor into the 1st shift register that is triggering the relay correctly, It causes the relay no to work or the motor.
I’ve also tried swapping the shift registers to see if one was bad, but they function the same.
The motor only needs to move forward so I don’t really want to use a motor driver board, But I’m lost as to why this is happening. Or even how to correct it. It seems that the Motor is shorting out somehow.
At last resort I guess I could run the motors from a relay, but this to me seems wrong, the Transistor array should function like that.