Thus begins my RV's automation project. When I am done, I plan to have multiple lights, slide outs, switches, and other devices all controlled wirelessly; either by 433Mhz transmitters and receivers, or (at the conclusion of the project), via WiFi by using a Smart Phone or Android Tablet.

This first installment is a remote controlled wall switch for my bedroom lights that can operate independantly to begin with, then integrate into the overall automation system. in fact, the automation system itself will be a modular collection of independant devices, but all networked together in the end. This approach allows me to build one part at a time, and the ability to make changes as I go along... as it is bound to happen.

I will be building a commercially available 433Mhz micro receiver with a "low-side" MOSFET output stage. The receiver is small enough that I will build the entire gizmo on the back of a JR Products wall switch.

I will be replacing the existing SPST switch with a SPDT switch - but no, I will not be creating a 3-Way switch.

While the above traditional 3-way switch may seem the way to go, there is a huge disadvantage when used in a RV environment. The primary reason is boondocking. You don't want a bunch of relays and receivers powered up when you are on battery power, which would be required if you were to use the above circuit. Rather, I will be using the 3 way switch to bypass the receiver and relay so that no power is consumed when the lights are off.

In this scenario, the wall switch completely bypasses the relay and receiver in the "UP" position. In the center position, everything is off. And in the "DN" position, control is transferred to the Receiver/Relay. So when boondocking, the UP position does not require any power to go to the Receiver/Relay, but on Shorepower, the DN position energizes and transfers control to the Receiver/Relay.

To build the switch, we will be using a generic Micro Relay Receiver. These are available via several brands and with varaious transmitters. But as long as they are 433Mhz and do not utilize rolling codes (like garage door openers do), then they can be mixed brand A vs brand B.

This is just a general purpose 3A diode, and the replacement above has a Vr=100V where the original had Vr=40V.

When you get the Receiver board, you may wish to make a change. The default mode for the board is "Latching". There are two other modes possible, "Momentary", and "Toggle". Descriptions of these modes are:

• Latching. Depress Channel A on remote to turn ON, Channel B on remote to turn OFF.
• Momentary. remote is ON only as long as Channel A or Channel B are depressed.
• Toggle. Depress Channel A to turn ON, depress Channel A again to turn OFF

For this project, I prefer Toggle as it only requires one button to control the device. Latching could be used if you don't want to modify the receiver board. And Momentary is not appropriate for this control.

Since these configuration pads are not accessible after soldering the receiver to the circuit board, you must make the decison and configuration prior to assembly.

Paring transmitters to the receiver. This can be done anytime as the programming pins will be accessible after installing the receiver to the circuit board.

• Short the programming pins on the top of the receiver board until the LED on the receiver is on steady.
• Release the short.
• Immediately depress the button on the transmitter you want to pair.
• The LED should blink a couple of times then go out.
• Test the paring by depressing the transmitter button. The LED should light showing activity.

Installation. When wiring/replacing an existing switch, you simply need to move the switch connections to the circuit board connections marked 12V and Output. They are "polarity" sensitive in the sense that the input and output cannot be swapped, even though they are on the +12V side. The only real trick is finding a path to ground. Fortunately in my RV, the 12V and Ground connections were available in the wall, as the circuit went to additional 12V devices.