The making of radio frequency sensor decoder.Automatic machine mirror

　　The transmitter includes a door opening sensor, a motion detector, an arming remote control, and a wireless keyboard for programming the alarm box. It turns out that no two of these devices use the same synchronization length or bit duration. Apart from the length of the message, the only thing in common is the basic format of the bits. Each bit occupies a fixed period of time, and the difference between zero and one is the duty cycle of the high/low part.

　　The beautiful waveform shown above is not the first time I have received it. Because of the high traffic in the 433 MHz band, I had to make sure to activate the sensor before setting the oscilloscope to perform a trigger. Fortunately, as long as the key is activated, the sensor will activate multiple copies of the data message, and the remote control and keypad will continue to output messages. By using an oscilloscope, I was able to determine the synchronization length and data bit duration of each project. As mentioned earlier, the synchronization time is different, and the bit time is also different, but the message format has low-level synchronization, followed by 24 data bits and a stop bit. This is enough to allow me to build a universal decoder in software without having to hard-code all the different details of each device.

　　I originally built the sensor decoder using PIC microcontrollers and assembly language. I have been playing with Arduino variants recently, so I want to see if I can replicate it. A simple schematic diagram is shown above, and there is also a picture of my prototype. What I did was to connect the Arduino Nano to the RF receiver board using three ordinary jumper wires. Only a power supply and a data cable are required.

　　If you read my Instructable on "Three in One Time and Weather Display", you will find that I am using a 433MHz universal RXB6 receiver. You may be able to make a really cheap receiver work within the short distances required for this project, but I still recommend a super heterodyne receiver.

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