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Topic: [solved] Help reading data sheet (Read 538 times) previous topic - next topic

fkeel

Jul 09, 2011, 11:00 pm Last Edit: Jul 09, 2011, 11:50 pm by fkeel Reason: 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 http://www.pololu.com/catalog/product/960/pictures

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:

http://www.sparkfun.com/datasheets/Robotics/QRE1113-Analog-Breakout-v11.pdf
http://www.pololu.com/picture/view/0J614

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...

AWOL

#1
Jul 09, 2011, 11:19 pm Last Edit: Jul 09, 2011, 11:20 pm by AWOL Reason: 1
Page 3, "Input diode" Vf 1.2 to 1.6V at 20mA.
Suggest you take 1.4V.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

mmcp42

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
there are only 10 types of people
them that understands binary
and them that doesn't

fkeel


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 :-) ... I might be back with more questions.

p.

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