- Dec 16, 2018
- Reaction score
Good catch. To expand on this. On the goby hat if you are using the 12v section you are using the uln2803 to drive your motor. This isnt really what this chip is for. This chip is meant to drive small coils i.e. a relay board. It has built in diode suppression to prevent reverse current spikes thru a coil. Its not really meant to run motor loads.I think that might be your problem there. The 12V pins direct from the Hat may not have the current to run your doser pump reliably. The Hat puts out low current 12V for relay switching purposes only, not designed for running equipment.
Try hook it up via a relay and proper 12V power supply and see if you still have the same problem.
A motor draws a large current spike for an instant until it starts moving then its current levels off. Without going into a long explanation on motor theory, depending on where exactly the motor stops, this starting current changes the next time the motor starts. You may be on the edge here where most times the motor starts but maybe not every time.
What are the specs on your doser pump?
Its a 12V pump but how much current does it take to run it reliably?
As @Des Westcott says the best way to do this is to have the hat drive a relay and have the relay switch a suitable 12v supply for the pump.