I am trying to use an Arduino Uno to separately control a 12V .5A solenoid, a 12V 1.5A solenoid, and a 12V 3A pump. I am currently using a TIP120 NPN transistor for each one controlled by the 5V output of the Arduino, but the pump transistor is getting hot after only about 30 seconds of runtime.
To reduce the heat, should I put two transistors in parallel and have a limiting resistor after to limit the current flow? As of now the pump is not pumping hard enough and I would like to get more current (?) to make it run harder. I know it can run harder if it gets the required energy. My power supply says that I am only drawing 2.6 A total for all three, (2 solenoids and a pump/motor) which are hooked up in parallel to the 12V supply and it seems to just max out at that, although at 12V, it says on the power supply it can supply 6A.
The solenoid transistors seem to be fine, the only issue I am having is with the pump transistor getting hot and not delivering enough current to make the pump go hard enough.
- Does the current or the voltage drive the motor? Or both?
- Would only having 1.5A flow through each transistor to get 3A to the motor be too much current?
- Do I need to put a resistor in line with the Arduino signal voltage? (Beta (DC voltage gain) for TIP120 is 1000 on datasheet)
- Should I get a bigger transistor? A MOSFET? Which one?
- Should I get a relay instead? Which one?