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Author Topic: IR LED needs to transmit 38khz please  (Read 2268 times)
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Hi, I want to have an IR LED transmit a 38 kHz signal to. I want to be able to have the Arduino do it. This will then be detected from by a TSOP 1738 38 kHz IR receiver connected to the Arduino. That detection will then be will be used as a switch. Where once it is triggered another thing happens. This is the same as used on a robot in obstacle avoidance. My object will have the transmitter and receiver side by side and then when an object for example a hand passes in front of it and it detects something is there something else happens.

My question is can the Arduino send a 38 khz signal ot to the LED? I have done it with a Basic Stamp with the  FREQOUT command in pbasic. Anything like that in Arduino?
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You are probably better off using some kind of 555 timer connected to the IR LED circuit to create the 38kHz carrier frequency than trying to generate it with PWM [analogWrite() command]. Connect that timer to a digital pin. When you set the pin high, it will automatically oscillate at the correct frequency. It is a lot more accurate and the Arduino is freed up inside the pulses to do other work. Here is a page on 555 http://www.uoguelph.ca/~antoon/gadgets/555/555.html oscillators. You need to get the right resistor-capacitor combo to achieve 38kHz. This site provides a simple formula. Also, if there is going to be no actual data communication (other than a 'switch') b/w these 2 modules, there are probably easier ways to do what I think you are talking about using just 2 IR LEDS.
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Thanks for the information that page looks like just what I need I will build one tonight.    smiley

Thanks for your responce
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I have an 8-pin PIC which provides common frequencies used for IR transmitters.

See http://www.phanderson.com/picaxe/

External Infrared Transmitter, 38, 40 and 56 kHz


Peter H Anderson
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Thanks those look great I will have to order one when I get back to the states this Christmas Too bad I live in China. I may order now and pick it up when I am there.

Also Peter you have a small dongle on the serial cable connected to the Arduino Solderless Development Package. Anyway I can get a schematic of that?

Thanks
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