Hacked Gadgets Forum

June 26, 2009

Hampton Bay Air Conditioner IR Remote Control Reverse Engineer

at 12:34 pm. Filed under Electronic Hacks

 

ElectronicsNerd shows us how to reverse engineer an IR remote control signal. By understanding what type of signal is being transmitted out of the remote control allows a microcontroller to simulate the code to control the Hampton Bay Air Conditioner.

"In the NEC protocol, the initial start pulse prepares the receiver IC for a data transmission at a particular rate, adjusting its AGC circuitry for the signal level excursions of what is to follow. After the standard 9ms equalization pulse, there’s a 4.5ms pause, and the receiver then accepts data at a predefined baud rate. If one weird spike were to occur at a particular moment during the transmission, the air conditioner might turn off instead of lower the setpoint temperature of the unit, without a means for detecting glitches in a transmission. Simple error checking like this provides for disallowing invalid input, while providing near-failsafe transmission of valid control data."