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RXD-433 • 3
THE RXD433
This wireless RF receiver/decoder has a 4 bit data output that will match the
data sent by the encoder, TXE433. The output is CMOS compatible when
the unit is run on +5 volts.
The demod bandwidth is selectable by the placement of jumpers on the
circuit board. The table on the schematic shows jumper positions for
different bandwidths. Narrower bandwidths will give slightly better range at
the expense of more limited constraints on battery voltage tolerance over
time and more limited operating temperature range. For most applications,
the 4800 Hz setting will be best.
The “decoder address select” allows you to use one transmitter to control
different receivers by giving each receiver a unique address. The decoder
chip has internal pull-up resistors making it a simple matter of grounding the
address select pins to match the grounded pins on the transmitter/encoder.
These outputs are also CMOS compatible when run on +5 volts.
The receiver/decoder unit additionally has a “data valid” output. This output
goes high when the “decoder address select” matches the encoder’s
address select. This is convenient place to connect a “data valid” LED
indicator to show at a glance when the receiver is decoding. The schematic
below shows how such an LED can be connected.
ANTENNA CONSIDERATIONS:
The simplest antenna consists of a piece of wire approximately 6 to 7 inches
long. If you desire more range you can try a ground plane antenna or a
Yagi such as the Ramsey 4004 model. The antenna should be tuned for the
433 MHz band for best operation.