Revo - Current/Voltage Sensor Setup

Overview

This page describes how to setup a voltage/current sensor using a Revolution or Revolution Nano board.

Hardware Connections

../../_images/voltage_current_connector.png
Color Connector pin (board) Description AttoPilot pin (sensor)
Black 1 GND GND
Red 2 Vcc Not used
Blue 3 Current input I
Orange 4 Voltage input V

Basic voltage sensor

A basic voltage divider can be used, two resistors connected between ground and plus from battery.

../../_images/voltage_divider.png ../../_images/basic_voltagesensor_connection_revo.png

For a 4S battery (16.8Volts) the following values can be used:

  • R1: 2,2 KOhms
  • R2: 10 KOhms

With Vbattery = 16.8V, Vout = (16.8 * 2.2) / (10 + 2.2) = 3,03V

See also http://en.wikipedia.org/wiki/Voltage_divider

Current / Voltage sensor

../../_images/CurrentVoltagesensor_connection_revo.png

Here is a list of common Attopilot sensors that can be used:

Module Type Sensitivity VoltageFactor CurrentFactor VoltageZero CurrentZero
Attopilot 13.6V/45A 242.3mV/V, 73.20mV/A 4.127 13.661 0 0
Attopilot 50V/90A [1] 63.69mV/V, 36.60mV/A 15.701 27.322 0 0
Attopilot 50V/180A 63.69mV/V, 18.30mV/A 15.701 54.645 0 0
[1]Same as RCTIMER 90A current sensor

For custom sensor see the Calculate SensorCalibration values section.

Hardware settings

The first thing to do is to configure the hardware settings:

  1. Connect the board to your computer and got to the System tab in your GCS
  2. Browse the first part (Settings) and find the HwSettings UAVObject
  3. Enable the Battery module: OptionalModules > Battery > Enable
  4. Set the analog input pins for voltage and current:
    • ADCRouting > adc0 > BatteryCurrent
    • ADCRouting > adc1 > BatteryVoltage
  5. Save changes, click Upload button
  6. Reboot your board: disconnect all power sources and reconnect to your computer.
../../_images/uavobrowser_HwSettings.png

Calibrate sensor

Now connect the battery to the battery sensor, if changes are done and battery module enabled you can see the display on PFD:

../../_images/PFD_volt_amp_display.png

But values displayed are not accurate, we need to calibrate sensor!

Calculate SensorCalibration values

To configure the battery monitor, you need to calculate the SensorCalibration values.

For example, the documentation for Attopilot current sensor specifies the following information for each sensor type:

Sensor type Voltage sensitivity Current sensitivity
50V/180A 63.69mV/Volt 18.30mV / Amp
50V/90A 63.69mV/Volt 36.60mV / Amp
13.6V/45A 242.3mV/Volt 73.20mV / Amp

In order to use 50V/90A you’ll have to do the following:

  • Convert everything to Volt, so Volt/Volt and Volt/Amp:

    • 63.69mV/V / 1000 = 0.06369 V/V
    • 36.60mV/A / 1000 = 0.0366 V/A

  • Then calculate the values to insert in Voltage and Current Factors:

    • VoltageFactor = 1 / 0.06369 = 15.701
    • CurrentFactor = 1 / 0.0366 = 27.322

Those factors are start values that can be adjusted later from readings, generally sensor’s sensitivity are not so accurate.

Setting FlightBatterySettings Properties

  1. Connect the board to your computer and go to the System tab in your GCS
  2. Browse the first part (Settings) and find the FlightBatterySettings UAVObject
  3. Set the VoltageFactor and CurrentFactor as in the previous section.
  4. Set the cell Capacity if you want a warning to be issued when there are less than 2 minutes of flight time available; otherwise, set to 0.
  5. Set NbCells with the number of cells in series (2 for 2S, 3 for 3S, 3 for 3S2P)
  6. Set the Warning and Alarm thresholds if you would like a warning or critical alarm to be issued when going under the values that you specify.
  7. Save changes, click Upload button.
../../_images/Uavbrowser_FlightbatterySettings.png

Note

Sometimes sensor are not accurate with small readings, especially for current. A CurrentZero setting can be set: without any load change this value to obtain a 0 ampers display.