Week 4

IR Receiver

IR Receiver

This is a simple IR receiver circuit which plugs into a serial port of a computer. There are many other circuits of this kind, and most of them are even simpler, but this circuit has two major advantages: 

(1) it uses an Atmel AVR RISC microcontroller (an AT90S2313) instead of the usual PIC microcontroller

(2) it uses a Maxim MAX232 for the generation of valid RS232 levels.

Advantage 1: is, of course, only valid for all those AVR addicts which have this device (and the corresponding programmer) ready at hand and don't care about PICs and PIC programmers. 

Advantage 2: comes into play if the IR receiver has to placed at a great distance from the computer. The MAX232 is more likely to deliver valid signals over bigger distances than cheaper solutions.

The IR receiver can receive it's +5V supply voltage from the keyboard or mouse connector of the computer (either from an unused PS/2 port or via a pass-thru adapter). If the IR interface is placed at a great distance from the computer, I power it with an external stabilized 5V DC power supply instead of the PS/2 port.

The interface communicates at 19200 baud, unidirectional (that means, it only transmits data and does not care anything about data which the computer send), without flow control. For every level transition in the demodulated IR signal, it transmits a single byte which corresponds to the time since the previous transition, capping off at a value of 255. It works reliable with a Sony remote control (using the special Sony protocol), and I have also successfully tested it with an Onkyo remote control (I think this one uses the standard RC5 protocol, but I'm not sure). Decoding happens on the computer; I use PC Remote Control for this.

 

Appendix:

Infrared Receiver

Infrared Receiver to RF Transmitter Circuit

IR receiver sensor

 

 

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