I am powering my APM with two batteries, one for the outputs and one for the inputs. So I don't require the APM Power Module to power my board, but I would like to add V & I sensing for the the main power.
Question is, has anybody wired an ATTO sensor to the Power Management port? What issues will I run into?
From looking at the eagle files the APM PM port is on ADC 12/13 not ADC 1/2. Is that still V & I respectively?
The divider network is 1.5K to 13.7k in the APM PM unit and 1K to 15.7K in the ATTO 90A? Is that correct?
The AMP current sensing is fed into an OpAmp with a 73.2k (atto) vs 110K on APM PM. What's the range for the APM PM vs the ATTO (3.3v)
Maybe the best solution is to buy the APM PM unit and disconnect the power line?
Thanks for any help and advice :)
Replies
I've disconnected the 5V line from the regulator, it would be a good addition to have a soldered jumper or something to cut the supply if the voltage regulator is not required in your setup. I'm powering using a separate battery for the 'electronics'
To answer my own question. The APM PM scales 0-50V to 0- 5V (well theoretical max 4.93V 1.5K/(1.5K+13.7K)*50V ) and the current is 0-5V to represent 0 - 90A. The APM PM can only take a max of 18V due to the power regulator, so why not make the scale to say 20V for greater accuracy? the actual max output to the ADC @ 18V is 1.78V
The Atto sensor is less resolution as it scales to 3.3VDC.