Need Help wiring a photodiode to measure light

  • Thread starter JuanF
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  • #1
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Main Question or Discussion Point

Hi everyone,
I'm new to the forum and basically need help to build a little gadget to measure the intensity of light that passes through a tube filled with solutions of different dye concentrations.
I have a 10530DAL photodiode, and a light source. What I'm doing now is measuring the current from pins 2 (Output Vo) and 1 (OV Case). This works but the range is very narrow.
I have tried to add a battery to the other 2 pins (9V) but nothing happens. If I invert the battery the diode heats up.
I am not really interested in absolute values but in relative ones (what I want to calibrate is the "system" that injects the solutions).
I'm clearly doing something wrong and would greatly appreciate some help.
Thanks in advance,
Juan
 

Answers and Replies

  • #2
816
1
What you have there is more than a photo diode. There is an op amp included. If you apply +V against ground on pin three and -V on pin four (V being between 4 and 18 Volts) your performance should increase dramatically.
 
  • #3
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Thank you very much, 0xDEADBEEF!
Unfortunately, my ignorance is vast, and I do not know how to do that. Do I need 2 batteries? Or one would be enough?
Also, what does against ground mean?
Sorry for the ignorance and once again thanks a lot!!
Juan
 
  • #4
816
1
The ground is the case and also pin 1. Yes you need two batteries. So you put say +9V on pin three and -9V on pin four and connect the other ends of the batteries to the ground pin. This was just through a sloppy look on the specs you might want to check them yourself.
 
  • #5
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0xDEADBEEF,
Once again, many many thanks. I'll try that first thing in the morning!!
Juan
 
  • #6
berkeman
Mentor
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What you have there is more than a photo diode. There is an op amp included. If you apply +V against ground on pin three and -V on pin four (V being between 4 and 18 Volts) your performance should increase dramatically.
Like Figure #3 in this tutorial on current-to-voltage converters:

http://www2.arrl.org/tis/info/pdf/0708056.pdf [Broken]

.
 
Last edited by a moderator:
  • #7
1,758
56
What is the spectral output of your light source? What is the spectral sensitivity of the photodiode?

For instance, if you are using an incandescent light source with a high output in the infrared and if your photodiode has a high sensitivity in the infrared and if your dyes are relatively transparent to infrared, you may see very little variation in light transmission with color. You may have to filter out the parts of the spectrum you're not interested in, in order to get good readings.

An alternative method would be to use red, blue and green LEDs as light sources and use red, blue and green LEDs as photodiodes to pick up just those colors respectively. This would not only avoid any problems with unwanted spectrum but potentially giving you a good measurement of the color too.
 
  • #8
4
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To all, and especially 0xDEADBEEF:
Thanks so much. it worked like a charm.
JuanF
 

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