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I'm looking into making a small robot that will be Raspberry Pi controlled. One of the features I'd like to perform with the robot is moving to a certain area via infra-red sensors.

My plan is to have an IR emitter at one place and an IR receiver on the robot itself, and once the robot picks up a signal it will turn towards it.

The question that I have is about the hardware as I'm very (very very) bad with it.

I've found these receivers which look simple and cheap, 20Pcs IR Receiver Infrared Radiation Module 38kHz TSOP4838 DIP-3, although I'm not sure what the 38kHz would mean for a IR transmitter... does it simply mean it receiving waves with 38 kilohertz frequency?

One more thing that I've tried to get my head around is the transmitter (or emitter?) I've tried looking in the website I've linked to above (http://www.banggood.com/) for a IR bulb to emit the signal for the robot to pick up but couldn't find any (there were a lot of strange looking boards. Isn't it just a bulb like on the remote?) If you can, please help me find compatible IR transmitter for the receivers above.

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You might want to read the spec sheet. I found one here that covers several IR receivers in the same family. They have carrier frequencies from 30kHz to 56kHz. The one you linked to is specifically 38kHz. The carrier frequency can be further modulated to send your own coded signals, similar to the way an AM Radio carrier frequency is modulated to send an audio signal.

The corresponding transmitters have part numbers like TSALxxxx such as the TSAL6200. I couldn't find one on Banggood.

  • Thank you !, given that Il buy some of the TSAL transmitters, does it mean I simply have to connect it to its voltage range and it will emit IR light? Ive found some on ebay using the spec sheet you linked. Out of curiosity, what are those things then? banggood.com/… are they transmitters aswell? cause they look a bit different than the one in your picture and have 3 pins... – iSoda Jul 18 '15 at 3:58
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Infrared receivers tend to have everything on chip and in my experience come with 3 pins, VCC, Data, and Ground (check the datasheet for the pin order of your device),

VCC tends to be 5V which means that the output Data pin will also be 5V. However they tend to have an internal resistor between the Data pin and VCC so you typically connect a large resistor between Data and Ground to get a Pi safe 3V3. Check the chip you buy.

They recognise signals modulated at the frequency they are designed for, typically 38kHz. Usually they output 1 if no 38kHz signal is present and 0 if the signal is present. This inversion of normal expectation is called active low.

An IR remote signal is typically a series of 0s and 1s of the order of several hundred microseconds each.

The transmitter is generally different. It is active high and does not automatically modulate the signal. You need to switch the transmitter on and off 38000 times a second to send a 1 and leave if off to signal a 0.

Linux has a program called LIRC which handles all this for you.

If you want a more hands on approach my pigpio library has several examples for capturing IR remote signals at http://abyz.me.uk/rpi/pigpio/examples.html

It is also possible to use pigpio to transmit IR signals. I'll add an example if I remember.

  • Thanks for helping out! :) Il definatly make use of that library once il get the materials. just to make things clear, you have to run the transmitter few thausand times a second to signal "1"? also, is this banggood.com/… a suitable transmitter for the receivers Ive linked above? I cant find any clear answer.... – iSoda Jul 18 '15 at 10:27
  • Yes, I have switched the transmitter 38,000 times a second to transmit a 1, no transmission is required for a 0. The transmitter you link to will be fine. By the way, I am told, a good source of transmitters is a remote you are going to throw away. – joan Jul 18 '15 at 13:03
  • Why does the one I linked (as transmitter) have 3 pins on it though? – iSoda Jul 18 '15 at 15:16

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