More electronics projects on mikekohn.net here.

August 3, 2009

Introduction

Here is a small circuit and source code for a program that can shut off (or turn on) Samsung TV's. Basically it's just an IR transmitter with an Atmel ATtiny13 programmed to send the "power button" command over and over. This is actually a pretty simple circuit and program. The hardest part was find the spec for the TV. I originally found information on the net for some other remote control specs and built a circuit and firmware around them, but Samsung used their own protocol. I even tried pointing the real remote into an infrared detector and watching the waves on a 'scope, but it didn't help too much. My friend Brian Grote ended up finding this site for me: http://www.techdesign.be/projects/011/011_waves.htm which had the hardware level info on remote and http://lirc.sourceforge.net/remotes/samsung/BN59-00538A which I had found earlier had all the codes I needed.

The software works by creating the carrier frequency (39.2kHz) with a timer interrupt every 61 cycles @ 4.8MHz (that's double the speed of 39.2kHz.. first interrupt turns the 1/2 bit on, second turns it off). I programmed both the mute and power buttons of the remote but hardcoded the power button. The data section of the code tells the MPU how long to keep the carrier frequency signal on or off.

Now I can hide this under my sleeve and turn Samsung TV's on and off by pointing at them. Muahahaha :).

Pictures

Here is the small test circuit from the schematic below.

Schematic

Source code
remote_control.asm

Copyright 1997-2012 - Michael Kohn

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