In-flight current measurement

[rcelectronics]

I am interested in doing some In-flight current measurement and wondering if anyone know of a good way to do it. The part I am not sure how to do is the actual measure part.

Using a hall effect sensor comes to mind as possible, but I have not realy used them and am not familiar with there use. Any other ways? Any help would be nice.

David

[Comatose]

Are you using a brushed ESC or a brushless one?

If you're using a brushed ESC and don't need an extreme amount of precision then I suggest you measure the on voltage of the bottom FET and use the on resistance of said fet to determine the current.

I = V/R.

Basically, throw out any voltages over a couple volts (those would be the off time of the half-bridge) or synch with the gate drive.

Its kinda a quick and dirty solution, but it doesn't add resistance to the circuit, and its cheaper than a hall sensor.

The trick is finding the real on resistance of the FET, but some quick calibration with a meter (at temperature) is all that requires.


You can do the same thing with a brushless ESC, by measuring one of the 6 transistors, but in that case you pretty much have to synch it to the FET.

That isn't hard, by the way. Set up an interrupt tied to the gate going high, then delay a short amount of time to let the fet turn completely on and get your voltage.

[AndyKunz]

Making a "smart shunt" is the easy way. Use a shunt of pretty much any size, amplify the voltage difference, put that through an LPF (I usually use about 1/2 sec avg), and read the results with a cheap ADC or uC.

You can safe a few cents by doing the LPF in software. I prefer to do it in hardware because I can adjust the circuit at the field if I need to.

Andy