Power Module (Voltage divisor & Ampere per Volt)

Navio / Edge Hardware
1

Hi Guys

I have got my Navio2 working great on my HexaCopter.

I am using a 4S 5000Mha Battery. I am powering the board via the power module. The voltage reported was very close to correct using the default divider of 10. I measure with my multi-meter and got a more exact one of 11.05. The current how ever seemed to be under reading massively, i used a current clamp from work over one of the battery wires and tried calibrating the Ampere per volt value it would seem 150 give me realistic results. I will try powering the copter form a bench supply with a multi-meter in series and confirming this ratio next week but was just wondering if i am doing something silly or if this is a ratio is more or less expected. it almost feel like this is factor of 10 out.

And advice or input on what other are using for these 2 values would be greatly appreciated.

Cheers

2

Hello,

I don’t know if this could help, but under 3A the amp meter of the navio is not reliable. To calibrate it correctly, you should draw at least 10A from the motors. Be careful with the propellers ! return them before processing.

3

Hello,

Same problem with my Navio2 and RPI2.

After calibration voltage reading is fine but Amp reading is like missing a factor 10.

Curr log is around 180 (18A is coherent with my config),
CurrTot log is around 10 times less that it would be.

CURRENT (battery voltage, current and board voltage information):
FIELD
DESCRIPTION
Thr
Pilot input throttle from 0 ~ 1000
ThrInt
Integrated throttle (i.e. sum of total throttle output for this flight)
Volt
Battery voltage in volts * 100
Curr
Current drawn from the battery in amps * 100
Vcc
Board voltage
CurrTot
Total current drawn from battery

Log extract:

CURR, 259985687, 0, 1264, 180, 5192, 63.6088, 0

CURR, 350385687, 0, 1236, 207, 5218, 116.7836, 0

CURR, 458886329, 0, 1371, 0, 5224, 147.6601, 0 (disarmed, end of flight)

Can you confirm if it is a bug or do we have to apply a factor 10 to the Amp per Volt param (170 for 17)?

Thanks,

Marc
2016-07-30 13-46-46.bin (2.5 MB)

4

Hello,

Some feedback:

After some flights to calibrate Current draw, Amp per volt param is 157.

Current sensor is from Emlid.

Marc

5

This still persists. Been verified over multiple installs…

Running latest Emlid Raspbian on Navio2/RPi3 with AC 3.4.6

Amps per volt on a 120A current sense with a 3.3v range should be 36.3 Amps per Volt.

Parameter must be set to 363 to read in the neighborhood of correct. Final value based on entering measured value was 340.

Not sure if this is a driver or software issue on the Emlid side, or an error in ArduCopter.

I have a test device that allows me to pull 14 Amps continuous so it’s not due to low side inaccuracies.

Voltage reading is fine.

EDIT: Forgot to mention I am running an AUAV module. And I have seen it with AttoPilot as well. This is not a problem on the power module side. Other than the swings in current readings. Still does not account for suspicious factor of ten error…

1 Like
6

Thanks for report. I’ll try to look into it as soon as possible.

7

Same here. Calculated a current factor of 128 by using an amp meter.