|
Radio
Remote Control
|
|
The
EFY July 99 issue carried an article on wireless calling
bell using VG40T and VG40R VHF remote control modules.
|
|
After
its publication many readers wanted me to develop remote
control switches to control mains load using these compact,
sealed VHF remote control 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 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. |
|
|
Click on the Image for its larger version
|
