power sensor for servo protection?

seen that some cheap power sensors are available at aliexpress.


Any chance I could use some of these to protect my servos? I think I would need to sum up the last 1 or 2 seconds of measurments to allow for short high phases?

Mats's picture

Servo protection

You can use this type of device, but it requres that software monitor both voltage and ampere and calculates some accumulated power / energy over some time. So if the algorithm is wrong the servo will burn anyway. You also need two extra cables for each servo and also two extra analog pins on the Arduino for each servo. So you may end up with lots of cables.

Juerg suggested using a Resettable Fuse polyfuse to protect the servos. They are cheap so you buy several sets of different sizes for less that the cost of a single servo. I bought the 3A version, but it's probably best to get several sets to try them out. Start with a low value and if they trigger during normal load, replace with a larger value. 



The nice thing with them is they will protect your servo even if the software fails, and they will reset automatically.


juerg's picture

Thanks Mats Yes I am aware of

Thanks Mats

Yes I am aware of my own suggestion to use fuses ;-). Knowing the voltage and power however might be of more use e.g. detecting that the servo can not reach its target position?

There was also a mentioning of an engineer I met that some robots calculate the power it needs to make a move and using more power than expected will stop the motion. Like robots that may get in contact with people and should not throw them over or hurt them.

Using distributed controllers (as your esp device or Nanos/Micros) and connect them wireless or over I2C the cabling issue might be a local thing and does not have to be routed through the whole robot.

And why not have the cpu's do some work while on power. It also might be easier to add a power sensor instead of an additional poti to detect movement.

Mats's picture

Power mesurements

Ahah. Stupid me. I didn't notice that you were the person posting this question.. Doh..

I agree to what you say. Knowing how much power each servo uses is a good thing and can be used as a measurement of how hard it's working. 

If you want have less cabling this device works directly over i2c. There is a service in MRL to use it. And the one you suggest will also work like you describe it.