24V on/off switch

Im planning to use some auxiliary equipment. It is a motor that runs of a 24V battery mounted on the ROV. But it requires a 24VDC on/off switch to run the motor. Can anyone give me a idea of how i can set that up?

Hi Jørgen,

You can use the switch to activate a 24vdc relay, which is where all the power will go through. So the switch only uses a small current to keep the relay open or closed as you like.

This is how I do it in my ROVs but with 12VDC 80A relays used with 16VDC and I don’t have any power problems, I have been using this system for 4 years with zero problems.


Hi, thanks. But i will need an actual switch on the ROV, like the one we use to turn on battery power to the control pod? I cannot activate a relay through QGroundcontrol?

Hi @Jhans,

You can use a Pixhawk AUX pin in “relay” mode (by default pins 5 and 6) to output a 3.3V signal, which can be controlled with the relay button functions. That signal can be used to switch a logic-level MOSFET (discussed here) or a relay, which can control the connection between your 24V supply and your DC motor.

The primary considerations are ensuring:

  • 3.3V is a suitable switching voltage for the switching hardware you choose
  • the current draw required for switching is <25mA (per the datasheet I/O max draw) - mostly a problem for relays
  • the switching hardware supports the current required by your motor, and its supply voltage

Hi @Jhans,

I use the switch https://bluerobotics.com/store/comm-control-power/switch/switch-10-5a-r1/ to activate an 80A relay to completely cut off power to the ROV.

But as @EliotBR says you can trigger an arduino relay with the Pixhwak. These relays usually have a maximum current of 30A, if you need more current, you can use the arduino relay to activate a relay with more ampers.