12 Replies Latest reply on Apr 23, 2013 5:48 AM by ki.leung

# measuring voltage using photodiode

how can i measure voltage of light with the help of photodiode.?

• ###### 1. Re: measuring voltage using photodiode

Light doesn't have a voltage. So can't be measured.

But you can detect the existance and brightest of light using photodiode. And if this is a research project. it should be easy to start with GOOGLE.

http://physlab.lums.edu.pk/images/1/10/Photodiode_circuit.pdf

But again. Not sure if that is what's required for your project, as it seems to keep on changing.

The best is to post the requirement or specification of project here.

As I mentioned before, it won't help as you are giving out information one bit at a time and no people here can't help without actually understanding your requirment.

It's all up to you.

• ###### 2. Re: measuring voltage using photodiode

Photon does have energy measured in electron volt, I think this is not what you want to measure.

• ###### 3. Re: measuring voltage using photodiode

HL: i have measure some reading below...plz have a look at it. i've used red led and measure its frequency at different distances

Distance(cm)       F(kHz)

0.5                             418

1                                 245

1.5                              125

2                                 73

2.5                              18

no light                       10

since u know that i m using tsl235 whose output frequency range is aroun 250 (+- 50) kHz for 670nm. and i think i m getting correct values. what do u suggest.

and if its correct can u plz help me out why measuring light frequency is better approach in psoc then with any other conventional microcontroller.

• ###### 4. Re: measuring voltage using photodiode

so let's control

@1cm you get 245 - 10 = 235kHz. at a distance of 2cm we expect a quarter of that value

= 235 / 4 + 10 = 68.75 which is already quite near to your measured 73. These differences may come from the LED-collector-lense.

Bob

• ###### 5. Re: measuring voltage using photodiode

Bob: what u suggest these values are correct?  and can u help me why my approach of measuring light with psoc is better then nay other conventional microcontroller

• ###### 6. Re: measuring voltage using photodiode

The dark offset is <=10 Hz, not Khz.

Regards, Dana.

• ###### 7. Re: measuring voltage using photodiode

Dana ya its less than 10 Hz

• ###### 8. Re: measuring voltage using photodiode

DAna: its 10 kHz.

i need to ask one more thing dana when i m working on AN2283. and doing its hardware connection. its display on lcd is not changing

its showing

underrange

fffff  0000f

can u tell me why so.??

• ###### 9. Re: measuring voltage using photodiode

I am confused. voltage reading in HZ?

• ###### 10. Re: measuring voltage using photodiode

Sensor converts light level to frequency.

Post you project here and forum, will take a look at it.

Regards, Dana.

• ###### 11. Re: measuring voltage using photodiode

By the look of the data, it looks like it is measuring the distance between the light source and the sensor. But not sure if that is the what it actually is. I hope we are not leading Ishu to a wrong direction. And if it is a project, then wasting time in the wrong path.

• ###### 12. Re: measuring voltage using photodiode

This is the sensor -

Regards, Dana.