# Cypress Developer CommunityTM

## measuring voltage using photodiode

Summary: 12 Replies, Latest post by danaaknight on 23 Apr 2013 07:21 AM PDT
User
72 posts

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

User
1362 posts

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.

User
1362 posts

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

User
72 posts

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.

User
9241 posts

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

User
72 posts

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

User
7646 posts

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

Regards, Dana.

User
72 posts

Dana ya its less than 10 Hz

User
72 posts

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.??

User
1362 posts

I am confused. voltage reading in HZ?

User
7646 posts

Sensor converts light level to frequency.

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

Regards, Dana.