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### Topic: Led sensor (Read 484 times)previous topic - next topic

#### eaj

##### Jul 21, 2011, 03:15 am
I have an application that I want to read an IR sensor connected to A0. I would also like to power an IR LED from PIN 13. The problems are:
For the PIN 13 I don't want the full 5v output. Is there a way with programming to give a 2.2v level?
For A0 I want to be able to adjust the threshold to control PIN 3 to go high when the threshold is met.

Any examples of code that may help?

Thanks!

#### AWOL

#1
##### Jul 21, 2011, 08:54 am
Quote
For the PIN 13 I don't want the full 5v output. Is there a way with programming to give a 2.2v level?

No, but you could use a simple voltage divider, but it sounds more like you just need a simple current-limiter. Can you explain why you think you need a 2.2V level?

Quote
For A0 I want to be able to adjust the threshold to control PIN 3 to go high when the threshold is met.

Code: [Select]
`digitalWrite (3, analogRead(A0) >= myThreshold);`
"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.

#### eaj

#2
##### Jul 21, 2011, 01:41 pm
For the PIN 13 I don't want the full 5v output. Is there a way with programming to give a 2.2v level?
No, but you could use a simple voltage divider, but it sounds more like you just need a simple current-limiter. Can you explain why you think you need a 2.2V level?

The IR LED is 2.2V. But you suggest I do this in hardware?

Thanks! I'll try this!!

#### AWOL

#3
##### Jul 21, 2011, 02:03 pm
Quote
The IR LED is 2.2V. But you suggest I do this in hardware?

The usual way, with a current-limiting resistor.
Assume 20mA, so
5 - 2.2 / 0.02 = 140 ohm
Go for a 150 ohm, or to be really safe, a 220ohm.
"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.

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