Analog value for IR Photodioide?

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi, I have been trying to set up an arduino to measure Infra Red (how much) using an Osram SFH 203 FA but with ZERO results !!

I have tried a few variations but basically I am using the AnalogReadSerial sketch with the photodioide positive going to arduino analog pin 0 and the photodiode negative going to arduino GND - clearly wrong? I just get a bunch of values the same as if nother is connected.... any pointers would be great :slight_smile:

2

Try this as a start:

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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons

3

Hi RuggedC,

Thanks for the pointer - I have tried it but I just get values in the serial which slowly fall from about 500 with no response to anything?

May I check the below with you - sorry, very basic.

PhotoDiode Long leg to Arduino Analog pin 0
PhotoDiode Short leg to Arduino GND
PhotoDiode Long leg to Arduino +5v using 10K ohm resistor

Using this code:

void setup() {
  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(0);
  Serial.println(sensorValue, DEC);
  delay(1000);
}
4

Flip the photodiode around :slight_smile: Short leg to analog pin 0, long leg to GND.

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The Quick Shield: breakout all 28 pins to quick-connect terminals

5

Ooops..

Now wired as below but I get the same result?

PhotoDiode Short leg to Arduino Analog pin 0
PhotoDiode Long leg to Arduino GND
PhotoDiode Short leg to Arduino +5v using 10K ohm resistor

6

Then try a 100k resistor.

Also, how are you illuminating the photodiode? Do you have a strong source of IR light, as visible light is being filtered out. The sun should work well (if it's daylight where you are :sunglasses: )

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Need a custom shield? Let us design and build one for you.

7

No change but I tried the same setup on a 328 board (I was using a 168) and now I'm getting results :slight_smile: The value is high when the is no IR and low when there is... is this right?

Not sure about the 168 board - it should work the same I guess?

8

Odd...it should work the same. Though the circuit is very sensitive to leakage currents (we're in the microamps range here) so perhaps there is enough part-to-part variation to allow one board to work and another not.

Really, a more robust solution for photodiode interfacing is the transimpedance amplifier, but I figured a simple resistor circuit would be enough for a short-term test:

http://electronicdesign.com/print/analog-and-mixed-signal/what-s-all-this-transimpedance-amplifier-stuff-any.aspx

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons

9

Thanks for your help - very much appreciated. My ultimate goal is to record when a wood burner is on and to what degree (without contact) - I figured infra red is the way to go but I need to do some testing - now that I can get some sort of sensor output I can see how it might help me record the info I'm looking for.

Thanks again :slight_smile: