Transmitterˇ@
Introduction of Transmitter
This is a four-button remote control and is widely used in security
system for properties and vehicles, garage door openerˇK etc. Its remote
distance can reach 200 meters. Since most applications require remote distance
of only 50 meters; therefore, remote distance is usually not a main factor when
selecting a remote controller but the price, size, total outlook, energy
consumption, and reliability.
This
size of this transmitter is only 58mmx 38mm x 8mm. The shell is made with peach
tree patterned plastic. To avoid mis-pressing the buttons, a protection cover is
equipped. The antenna is about 13cm long and it weights only 20 grams.
Transmitter
In
the above diagram, you can see that the transmitter has four buttons A, B,C,D
and a LED. A saw resonator is installed in this device to transmit frequency.
The circuit is basically a radio frequency (RF) oscillator that operates around
315MHz (315 million cycles per second). The frequency is normally stable. It is
good for multi transmission since there are four different transmitting signals.
In the market, there are some low-price remote controls that are equipped with
LC oscillator. Those transmitters are not as stable as the one we will use in
this project; even they are using a high quality tuning capacitor. Their
frequency stability and transmission distance will be affected after vibration
or a sharp change in temperature.
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