433 MHz Super Remote

(fine print: this design may exceed some legal restrictions in some countries)

Using a PIC12F683 and a few transistors, it is theoretically possible to boost the power to a standard 433 MHz remote transmitter module. (Note hypothetical image at right).

This design utilized 10 Pulse Coding for maximum range with minimal power draw. Very short pulses are generated using a voltage multipier circuit described below.


 

The Circuit

The pic is normally in sleep mode with both the Boost and Pulse outputs set low. When any of the buttons is pushed activating the interrupt-on-change function, the unit wakes up.

After determining the proper code to transmit, a 100 microsecond boost signal turns on Q3 pulling the negative end of C1 to ground while the positive end (A) is held near 12 volts by CR1. The boost signal is terminated and the pulse signal is activated causing Q1 to turn on Q2 raising the negative end of C1 to 12 volts and forcing the positive end of C1 to nearly 24 volts.

Since the base of Q4 is tied to 12 volts it only conducts when its emitter is raised above 12 volts by the pulse signal. The produces a clean 0 to 24 volt pulse on point (B) to power the RF device.

Included here are the Source file, Hex file, Board layout, and Parts placement.