ELM622 Просмотр технического описания (PDF) - Elm Electronics
Номер в каталоге
Компоненты Описание
Список матч
ELM622 Datasheet PDF : 5 Pages
| |||
ELM622
Example Application
Figure 1 shows an example circuit using the
ELM622. Keypresses on a television remote control
transmitter are received by this circuit, interpreted, and
retransmitted to a monitoring computer.
The television remote control used is one of the low
cost universal types, set to generate Sony™ codes. This
is often the default power-up mode for most of these
remotes. Output is by way of a simple one transistor
RS232 connection, with no handshaking. The auxiliary
reset output is not used in this case, and power for the
entire circuit is provided by a 5 volt regulated supply.
Operation is straight-forward. When a button on the
remote is pressed, the serial data stream is detected by
the infrared module and passed onto the ELM622 as a
series of negative-going pulses. The data is then
decoded, and if found to contain a Sony™ control code,
is retransmitted. The type of receiver modules required
are commonly available on the market, and are
manufactured by companies such as Sharp™ or
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 ELM622’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.
The output of the ELM622 is shown coupled to a
monitoring computer through a simple one transistor
buffer circuit. The circuit uses the computer’s idle
transmit line as a source of negative voltage, and
includes a diode for protection from backfeeds. Output
connections are made through a standard DB25 female
modem type connector with the pin numbers as shown.
This is all that is required to receive control codes
from a standard infrared remote control, and to transmit
them to a computer. At the computer, the data can be
displayed using a terminal program, used to control the
computer, or possibly used to control other devices.
Alternatively, the ELM622 could simply be connected
directly to a microcontroller, providing a very low parts
count alternative to the use of keyboards...
+5V
+12V
0.1µF
78L05
+5V
0.1µF
10KΩ
1
8
2
7
3
6
4
5
40 KHz IR
Receiver
4.7KΩ
2N3906
3
4.7KΩ
7
1N4001
2
DB25F
Connector
560Ω
LED
ELM622DSA
Figure 1. Infrared to RS232 Circuit
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
5 of 5
Share Link: 