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UHF Remote 2-Channel 230VAC Power Switch

If you're looking for a mains "switch" which can be operated from some distance away, this low-cost, simple project could be just what you want. With a UHF remote control and two switched "channels", it needs very little power thanks to the use of latching relays.

By Ross Tester
Design by Branco Justic#

There are countless applications – especially with colder weather coming on – where it would be nice to turn mains devices on and off remotely.

Imagine being able to switch something on and off without having to go close to it – outside in the wind and rain, for example. Imagine being able to control two devices, completely independently.

You’re imagining exactly what this device does. It has an IEC mains input connector (so uses a standard IEC power cable) and two standard 3-pin mains sockets, into which any mains devices (up to 2300W total) can be plugged and controlled.

It’s housed in a standard plastic case with the only other control an on/off switch.

The number of channels you construct is optional. The prototype was made with two channels but if your application only needs one channel, you simply leave a relay and a few other components out.

It’s a true remote “switch” – you press one button on the pre-built UHF remote control keyring transmitter to turn one of the relays on, then press another to turn it off. The transmitter has four buttons on it, therefore it can control two channels.

It has a nominal range of up to about 80 metres, perhaps more and this should be more than enough for most applications. But this range can be significantly extended with an optional module, which we will look at a little later.

And speaking of relays, they’re not your garden-variety types. Each has a contact rating of 80A – much more than is available from a standard power outlet (10A).

But more importantly, they’re latching relays which only require a short-term power pulse to turn them on or off. The advantage of this is that once actuated, no power is required to keep the relay “pulled in” – so you don’t waste a lot of power if something needs to be left on for a length of time. We explain how latching relays work in a separate panel.

Like the transmitter, the UHF receiver module is pre-built, thus avoiding any setup problems.

Click for larger image
The three main components of our UHF Mains switch: (left) the UHF receiver module, already attached to the main PC board and (right) the UHF transmitter module with its case behind.

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