ELM339P View Datasheet(PDF) - Elm Electronics
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Description
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ELM339P Datasheet PDF : 4 Pages
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ELM339
Example Application
Figure 1 shows a typical control circuit that uses the
ELM339. Relays are driven by each of the outputs,
providing isolation, and current carrying capability.
Transistor buffers are used to interface the circuit to the
12V relays.
All three of the outputs are used in the latching
mode, in this case. Converting Out7 (pin 3) to pulse
mode is easily accomplished by connecting pin 4 to 5V
rather than circuit common as shown. No other circuit
changes would be required.
Circuit operation is straight-forward. A serial data
stream is detected by the infrared module and passed
onto the ELM339 as a series of negative-going pulses.
The data is then decoded, and if found to contain the
correct Sony™ control code sequence, the state of the
selected output will be altered. The receiver modules
required are commonly available on the market, and are
manufactured by companies such as Sharp™ or
1N4001
+12V
12V Relay
Output “7”
LiteOn™. A 40KHz module is required for a Sony™
infrared remote, although 38KHz ones have been used
successfully.
In operation, ambient light can occasionally cause
an infrared receiver’s bias level to drift towards VSS,
possibly tripping the ELM339’s schmitt trigger input. As
the receiver output drifts high again, the Schmitt trigger
may not always reset, so that it might appear that there
is carrier present when it is not. This condition is
accounted for within the integrated circuit by
momentarily changing pin 5 to a high level output
before taking any measurements, thus reseting the
trigger. The series resistor must be used on pin 5 to
protect both circuits during this momentary high level
pulse. Typically a value of 4.7KΩ is sufficient.
Power supplies for this application are standard.
Regulated 5V is provided for the logic circuits, while
unregulated 12V is used for the relay coils.
1N4001
+12V
12V Relay
Output “5”
2.2KΩ
2N3904
+12V
0.1µF
78L05
+5V
0.1µF
40 KHz IR
Receiver
2N3904
2.2KΩ
1N4001
+12V
12V Relay
Output “3”
1
8
2
7
3
6
4
5
4.7KΩ
2.2KΩ
2N3904
560Ω
LED
ELM339DSA
Figure 1. Three Output Remote Control
Elm Electronics – Circuits for the Hobbyist
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