Digital Switch?

Hello everyone,

I have been recently working on a project and I need some help. I am using Arduino to control a flying device composed of four motors, the problem I am facing is that I need to connect the battery after a preliminary set up. I could connect the battery manually, but I’d rather have Arduino connect the terminals to each motor.

I was wondering if I could use and electronic device that could do that for me. Below you can see what I mean:

Also, it would be necessary for the switch to withstand currents up to 25Amps.




Hi Beliark.

You mean like this?

Driven with a switching transistor?

Thanks for the quick response patduino,

I am not familiar with switches so I am not sure how this one works. I just want to have to use one of the digital pins on the arduino board, and whenever the voltage corresponding to logical 1 appears, turn the switch on. Otherwise it should stay off.

I am not entirely sure if a transistor could do that without some sort of weird voltage to current relationship. I guess a relay could do. Is there such a thing as a logical relay??


Use a power mosfet, either a P-channel one switching the positive supply to the motors as in your diagram, or an N-channel mosfet switching the negative side - which is easier to drive and gives you a better choice of mosfets.

However, I suspect that you need to control the speed of your 4 motors individually. In that case, you can combine the on/off function with the motor speed control, avoiding the need for a separate electrically-controlled on/off switch (you'll probably still want a mechanical on/off switch for safety).

Another answer, dull and old fashioned, but very accessible, is the relay.

Help on these at....

.. which tells you about a "gotcha" you need to avoid being got by.

The Arduino output would go to the "Out" at the left of the diagram. It isn't as hard as it may seem from the limited info at the site above.

If you can stand having to watch a video clip...

If you can READ (!)... you can go to....

(GASP! It might have been easier just to write my own than to locate that! Google! There MUST be decent guides out there to this basic topic!)

patduino: You mean like this?

I think you will find that a SSR designed for use on AC line voltages is going to be useless with DC motors.

Thanks for the fact check. It looks like I pasted the wrong link. My bad. The design needs a 25A DC relay, not this 240VAC one.

patduino: Thanks for the fact check. It looks like I pasted the wrong link. My bad. The design needs a 25A DC relay, not this 240VAC one.

The key here is not the voltage, it is the difference between DC and AC. SSRs for AC use SCRs or Triacs. That's not going to end up well for DC.