Controlling pump with Digital pin, but use another power source

Is this possible?

I have programmed a pump to start at a certain point connected to Digital PWM 12, but it doesn't seem to get enough power to start..

So my question is; is it possible to use Digital PWM 12 to start and stop the pump, but power the pump from external source? If it's possible, then how?

Post a schematic and a DB to the pump in use.

Hi @fedda123
In your good conscience, do you think that someone would be able to help you with this information you posted?
Please read the highly enlightening topic:
How to get the best out of this forum.

Then redo your initial post and then we might be able to help you.

RV mineirin

What Arduino? Pin 12 is NOT a PWM pin on most. What current does the pump require?


What Arduino board has a PWM pin 12?

You can use a MOSFET motor driver to power the pump from an external power supply but control the pump with the Arduino PWM.

Choose the motor driver based on the stall current of the motor and the motor supply voltage. The stall current can be several times the running current. The stall current will be drawn, briefly, every time that the motor is started. The stall current should be listed in the motor data sheet. In the absence of a data sheet, the stall current can be estimated. To estimate the stall current, measure the motor winding resistance. Take several measurements rotating the motor a bit between readings. Use the lowest reading in the calculation. The estimated stall current is the motor supply voltage divided by the measured resistance.

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Well, maybe I didn't formulate my question quite right, or I might not have enough experience..

I'll try again, with a bit more information.

Pin A0 to A4 is connected to a soil moisture sensor:

Pin 12 is connected to a pump(3v) and a solenoid valve(3v)

So, I wonder. Is it possible to run the pump and valve from an external power source, but still get the Arduino to tell when to turn on/off?

Sorry if it doesn't make any sense, but hopefully you understand what I want :wink:

Yeah, a MOSFET is probably what i need..

How much current does it need?

The datasheet doesn't say, but measure with a multimeter it says
Pump = 4A at 3.3v
Valve = 3.5A at 3.3v

Use a MOSFET or motor driver. Trying to run that off your Arduino could kill it.

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and neither pump nor the valve would work....

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