Stepping down a 5v circuit to 3.3v for ADC input

I am planning my RC build and I’d like to hook up two servos with an analog feedback to the ADC on Navio. From what I understand the ADC runs at a reference voltage of 3.3v, but the servo runs at 5v so I’m imagining that the analog output can be anywhere from 0-5v.

What is a good way to step down the voltage? Would a simple voltage divider with something like R1 of 10kOhm and R2 of 20kOhm work?

@ajr Yes, a simple divider will do the job.

Great, thank you for the help.

What do I need to do to get this to work with Navio+?

that has 5V ADC and I need 3.3v.

That means that you will be able to measure up to 3.3/5 * range. Navio2 has 6.6V ADC range.

I am still learning a lot and not sure what that means.

That power module is calibrated for a 5V ADC, which means that at max current it will show voltage of 5V on current measuring pin and 5V at voltage measuring pin. At zero current and voltage it will show 0V on both pins. Navio+ can only accept up to 3.3V on its ADC, so you need to account for that. Simply scale the max range of the power module, 3.3V/5V = 0.66 . So for Navio+ ADC max input of that power module will be 0.66 * 42V = 27V. Same with current.


where do I enter in the scale value? Or do I use hardware for this?

Can I plug in the 5v cable into the navio+ if I’m not concerned with battery voltage while I’m getting everything setup?

or if there is already a post talking about this I could be pointed to?

The scale value that I have calculated in previous reply is derating value, so it is just showing you what will be the max measurement range.

Yes, you can power it from the power module, servi rail or USB. The 3.3V range is just for the ADC measurements, not for power.