Air Data Sensors

The following wiring is necessary to connect a sensor to the autopilot:

The LM335 sensor can share voltage supply with the Autopilot REx. However, the impedance of the resistor R must vary with the voltage; since the sensor requires a forward current between 0.4 and 5 mA to operate. We recommend to use a resistor as high as possible complying with the folllowing equation:

Where R is the value of the resistor (ohms) and Vin is the supply voltage (V). The following table shows a list of examples of a tested resistor for each voltage supply. Obtaining an error average of 1.5 °C.

The Vout pin has to be connected to an analog input of the Main connector.

• Users must choose one analog pin to connect:

  Connector J1 harness			LM335 sensor
  PIN	Signal	Color code	Signal
  14	ANALOG IN 1	Brown - Green	Vout
  15	ANALOG IN 3	White - Yellow
  22	ANALOG IN 5	Brown - Blue
  44	ANALOG IN 2	Brown - Green
  45	ANALOG IN 4	White - Yellow
  52	ANALOG IN 6	Brown - Blue

  
  

• Users must use the supply voltage according to the Autopilot REx being used:

  Connector J1 harness			LM335 sensor
  PIN	Signal	Color code	Signal
  3	VIN PRIM	Green	V+
  5	VIN MON	Gray
  8	VIN PRIM	Red

  
  

• Users must choose one ground pin to use:

  Connector J1 harness			LM335 sensor
  PIN	Signal	Color code	Signal
  1	GND MON	White	GND
  2	GND PRIM	Brown
  7	GND PRIM	Blue
  26	J1 GND IO	Brown - Black
  29	J1 GND IO	Pink - Green

  
  

Once connected, the temperature can be monitored in 1x PDI Builder by using the variables ADC0 to ADC4. The wiring explained previously obtains a relationship of Temperature and Vout as follows:

Where T is the measured temperature (in °C, since 273 is substracted in the formula) and Vout the output voltage of the previous circuit.