Remote Control Circuits
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Remote control using VHF modules
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A few designs for remote
control switches, using VG40T and VG40R remote control pair, are shown here.
The miniature transmitter module shown in Fig. 1, which just measures 34 mm
x 29 mm x 10 mm, can be used to operate all remote control receiver-cum-switch
combinations described in this project. A compact 9-volt PP3 battery can be
used with the transmitter. It can transmit signals up to 15 metres without any
aerial. The operating frequency of the transmitter is 300 MHz. The following
circuits, using VG40R remote control receiver module measuring 45 mm x 21 mm
x 13 mm, can be used to:
(a) activate a relay momentarily,
a relay for a preset period,
(c) switch on and switch off a load.
activate a relay momentarily (see Fig. 2), the switch on the transmitter unit
is pressed, and so a positive voltage is obtained at output pin of VG40R module.
This voltage is given to bias the relay driver transistor. The relay gets activated
by just pressing push-to-on micro switch on the transmitter unit. The relay
remains energised as long as the switch remains pressed. When the switch is
released, the relay gets deactivated. Any electrical/electronic load can be
connected via N/O contacts of the relay.
To activate a relay for a preset
period (refer Fig. 3), the switch on the transmitter unit is pressed momentarily.
The transistor gets base bias from VG40R module. As a result the transistor
conducts and applies a trigger pulse to IC 555, which is wired as a monostable
multivibrator. The relay remains activated till the preset time is over. Time
delay can be varied from a few seconds to a few minutes by adjusting timing
To switch on and switch off a load (refer Fig. 4), a 555 IC
and a decade counter 4017 IC are used. Here the 4017 IC is wired as a flip-flop
for toggle action. This is achieved by connecting Q2 output to reset terminal
while Q1 output is unused. Q0 output is used for energising the relay. The relay
is activated and deactivated by pressing the transmitter switch alternately.
So, to activate the load, just press the transmitter switch once, momentarily.
The relay will remain activated. To switch off the relay, press the transmitter
switch again. This process can be repeated. Time delay of monostable multivibrator
is set for about one second.
Note: Short length of shielded wire should
be used between VG40R receiver module output and the rest of the circuit. The
transmitter with 9V battery must be housed inside a nonmetallic (say, plastic)
cabinet for maximum range of operation.
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