Remote RF Transmitter

 

This device was built into a small (1 1/4 by 2 inch) Radio Shack project box. It features four push buttons which can produce 2 codes each. (Pushing a button for less than one second sends the first code, holding it for over one second sends the second code.)

Utilizing the PIC Sleep mode, a 12 volt battery lasts over a year in this design.


 

Most of the components are mounted on a small PCB fabricated just for this use. The battery (lower left) and transmitter module (lower right) are mounted off the circuit board itself.

Note the plastic 'shoulder washers' in the top piece. They rest on the buttons and are cut off even on the outside of the box.

 

No power switch is required, any of the 4 buttons will wake up the PIC from sleep mode. Also, to save power, a zener is used in place of the standard 5-volt regulator.

The transmitter is driven from the ground side and powers the unit completely off when not in use. Note: using the 'data' input on the xmitter worked poorly and let it draw residual current.

A small amount of wire serves as the antenna inside the box.


 

The board layout is shown here. Blank parts of the board were cut out to make room for the battery and xmitter.

The Source File is included here. It was unfortunately lost at some point and had to be reconstituted using a dissassembler.