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Thursday, December 17, 2009

Interactive LED Test 2 - First Of The Modules

Ok so it's been a few months since the post on Interactive LED's. Even though I had already made a module and recorded a video, I had not had the time to upload the video or explain the circuit.



So below is a picture of the circuit in its most basic form. No LED protection for this simple circuit, however building more modules would require a far better design than the one shown...

Circuit Explination:

InfraRed light emmitting from the IR LED transmitter is beamed onto an obstacle (your hand/finger etc.) and reflected onto the IR Receiver (a reverse biased IR LED) which triggers the amplifier to turn on the green LED's.

In the circuit I am using an LM324 - Low Power Quad Operational Amplifier. This is due to the fact that the reflected IR creates a small voltage on the receiver (depends on variables however one test I did was around 150-200mV) and approx 16x gain so 2.4-2.6V on the output.



Being a Quad OP Amp, I had 1 Green LED per output.

Because I only made this module as a "Proof of concept" I have not gone any further with it... Hopefully when I get some time I might come back to this...

8 comments:

ASH said...

dude! th was gr8 and I tried using LDR but it was not working ...im passing same voltage for both inputs but for inverting one i attacked LDR before ,but it was not working??

ASH said...

heheh ,sry not attacked its 'attached'

Anonymous said...

good one.
the difference i felt between your design and the main idea is LED switch off timing.by using some capacitors if your could get some delay between the on off timing,then that would be amazing like wave.

Paul D'Intino said...

Thanks, yeah you're right adding caps would be a better effect. However, I only made this setup as it was the circuit in its most basic form.

Anonymous said...

any recommendation for
ir led

Paul D'Intino said...

I had a lot of 850nm IR Led's just kicking around. However, you could use any IR Led. Even the ones out of remotes will work well. Some are 940nm and I've tested them and they work just the same.

It's only a very small trigger voltage from the IR Receiver to the Input pin of the OP Amp, and providing you're not under direct sunlight, any frequency should work ok.

Anonymous said...

ok.i got 1r333 led's i hope they will work.
and iam planning to implement his in my dining table.i have to see whether it works even with the frosted glass place on the circuit.

Anonymous said...

its working good.
but not getting satisfied results if i place a glass over th circuit.
I think the IR receiver need to set some threshold value.is it possible if i place a pot at the LM324 input side of the sensor?