As the only electronics engineer in my =family and circle of
friends, it is some-times not possible to evade an appeal for help. This
time the request came from a friendly elderly lady in a retirement
home. In her room the light switch by the door and the pull cord above
the bed operate the light fitting on the ceiling in the middle of the
room. However, she would prefer that her standing lamp was operated by
these switches instead, since she does not actually have a light fitting
mounted on the ceiling. This standing lamp has an on/of f switch in
the power cord and is plugged into a power point. However, it stands
rather far from the bed so that she always has to find her way in the
dark. A wireless operated power point is not really a consideration,
because it is just a matter of time before the remote is lost. Or maybe
not?
Remote Control Mains Switch Circuit Diagram :
Behold a feasible circuit. Buy a wireless power point and an
enclosure that is big enough for the remote control and a small piece of
prototyping board. On the proto-typing board build the circuit
according to the accompanying schematic and (care-fully) open the remote
control and solder wires to the push buttons for ‘on’ and ‘off’.
Measure if these are polarised and if that is the case connect them to
the 4N25 opto-couplers as shown in the schematic, where pin 5 has a
higher voltage than pin 4.
The operation is as follows. The
lady operates the pull cord or light switch to turn the light on. This
causes the mains voltage to be applied to the transformer. The relay is
activated which charges C1. While C1 charges, a small current flows
through optocoupler 1. The result is that the ‘on’ button on the remote
control is pressed. The remote control switches the corresponding power
point on and to which the standing lamp is connected. The standing
lamp will therefore now turn on. Capacitor C2 is charged at the same
time. If the lady pulls the cord again, or if she operates the switch
near the door, the relay will de-energise and C2 discharges across
optocoupler #2. This operates the ‘off’ contact of the remote control
and the light goes out.
The remote control continuous to
operate from its normal battery and the white enclosure is attached to
the ceiling in place of the light fitting. Diode D1 ensures that C1 is
discharged when the relay de-energises. D2 ensures that C2 cannot
discharge across the relay, but only across optocoupler 2.
Author : Jaap van der Graaff - Copyright :Elektor
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