Electronic circuits > Radio > Remote control using VHF modules
Remote control using VHF modules
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,
(b) activate a relay for a preset period,
(c) switch on and switch off a load.
To 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 components.
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
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
Published on: 2004-08-21 (8341 reads)
[ Back | Home ]