[solved] Help reading data sheet

Using Arduino General Electronics
1

Hi everyone

I need some help figureing out this data-sheet:

http://www.fairchildsemi.com/ds/QR/QRE1113.GR.pdf

The component I am interested in is a sensor generally used for line-tracking. It has an IR led and a photodiode. The photodiode measures the amount of reflected IR light, giving information on reflectence / or distance of objects.

I want to build a small array of them, similar to this sensor-array by pololu Pololu - QTR-8A Reflectance Sensor Array

I cannot figure out the voltage and current consumption of the LEDs. I have no experience with reading datasheets, I am sure its in there somewhere, but I just cant figure it out.

If someone could take a look at it for me and tell me what the current & voltage rating of the LED in the sensor is, that would be really helpfull. (I would also apreceate if someone told me how to find this information.

The closest I can find to current & voltage are from the absolute Maximum Ratings:

Continuous Forward Current - 50mA
Reverse Voltage - 5V

however, I am quite sure that these are not the values I am interested in.

I would really apreceate some help

Thanks

p.

edit: here are two schematics of breakout boards for this sensor. I guess it might be possible to reverse engeneer the information I am interested in from them:

However, the sparkfun breakoutboard tends to get fairly warm - maybe its becouse of something else which is dodgy in my prototype - but still, I would rather figure out the actual specs, before reverse engeneering something...

2

Page 3, "Input diode" Vf 1.2 to 1.6V at 20mA.
Suggest you take 1.4V.

3

the analog breakout schematic has a 10k resistor for each diode
so that's 0.5mA each (ignoring voltage drop across the device)

the array however has 47k for the receiver - so that's 0.1mA (ignoring voltage drop across the device)

the transmitter array - I'm not surprised it gets warm!
that's 8 * 33 ohm resistors in parallel = 4 ohms
current is going to be up round an amp or so!!!

I'd go with 20mA for each, as that's where the data sheet shows "typical" values

4

Thanks guys. I thought that "input diode" referred to the light sensing element.

Anyway, thanks, this gets me a step forward... I am way out of my waters :slight_smile: ... I might be back with more questions.

p.