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HELP ME PLEASE!!!

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cool

New Member
I am a student. I have to do a project about infrared remote control of a wall-switch. It required to fix the frequency of the pulses generated from the IR LED and the receiver can only detect this IR single. :?
I would like to know how to do the frequency modulation of a IR LED? and how to demodulation of the receiver? As only a single switch has to be controlled, I would llike to find the simplest and cheapest circuit to do the project.
please help me..... :oops:
 

Nigel Goodwin

Super Moderator
Most Helpful Member
cool said:
I am a student. I have to do a project about infrared remote control of a wall-switch. It required to fix the frequency of the pulses generated from the IR LED and the receiver can only detect this IR single. :?
I would like to know how to do the frequency modulation of a IR LED? and how to demodulation of the receiver? As only a single switch has to be controlled, I would llike to find the simplest and cheapest circuit to do the project.
You don't frequency modulate the IR, you amplitude modulate it (at 100%, which means you simply turn it on and off). The common frequency for doing this is around 38KHz, and there are ready made receiver IC's freely available - your TV, VCR, and anything else you have with IR R/C will almost certainly use these.

The simplest way would be to use a 555 and IR LED for the transmitter, and an IR receiver IC for the receiver. The only problem with this is that any IR R/C would trigger it - to avoid this you need to encode the transmitter, and decode in the receiver. Have a look at my IR PIC tutorial at http://www.winpicprog.co.uk which gives details using PIC's, Holtek also make a range of IC's specifically to do this.
 

0mega

New Member
"Cheap" method

Try using a DTMF encoder/decoder pair ...

This will give u 16 separate codes....
 

Sebi

Active Member
Big advantage to use a ready-made IR receiver modul as Nigel suggested. But if You need only one command, also useable a low frequency (e.g250...300Hz) on-off modulation of 38kHz, and in receive side for recognization a simple tone decoder PLL LM567.
(I just say this, because cannot programming a PIC...)
 

cool

New Member
thanks all guys!!~ :p
I will try to use NE555 to generate a 40kHz pluses for the tx side and use LM567 to do the decode in the rx side~
hope i can success... :wink:
 

cool

New Member
o... i don't know how to build the circuit for the rx of the remote control when using PIC!
I only have to control 1 switch, any simple common assembly that i can use??
do i still ve to set the frequency by 555 in the tx part????

:oops: :oops: :oops:
 

Nigel Goodwin

Super Moderator
Most Helpful Member
cool said:
o... i don't know how to build the circuit for the rx of the remote control when using PIC!
I only have to control 1 switch, any simple common assembly that i can use??
do i still ve to set the frequency by 555 in the tx part????
Have a look at my PIC tutorials I mentioned above, I give circuit diagrams, veroboard layouts, and all the source code. There isn't one which does exactly what you require, but it would be trivial to make it so.
 

Phasor

Member
Off-topic, but 0mega, did you notice that the circuit in your avatar performs no function whatsoever? It is always off! :?
 
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