Pengenalan Infrared
By Mr. Widodo
Dari berbagai sumber
Simple IR transmitter circuit
Transmitter circuit information
This is an IR transmitting circuit which can be used in many projects (I
designed this to try to make my 3D glasses wireless). This IR transmitter sends
40 kHz (frequency can be adjusted using R2) carrier under computer control
(computer can turn the IR transmission on and off). IR carriers at around 40
kHz carrier frequency are widely used in TV remote
controlling and ICs for receiving these signals are quite easily available.
The circuit can be controlled using any TTL or RS-232C level control signal
which makes the interfacing very simple. The circuit can be used for example
for using computer to generate IR remote control signals or experimental IR
data transmission.
The circuit works so that when the input (LEFT/RIGHT CONTROL) pin is in
logic high state (+4..15V) the transmitter is on and
when it is in logic low state (+1V..-15V) the transmitter is off.
Component list for IR transmitter
C1 1 nF
C2 10 nF
C3 220 nF
D1,D2 1N4148
D3 TIL31B (or other suitable IR LED)
R1 1 kohm
R2 22 kohm trimmer
R3 120 ohm
U1 NE555, LM555 or similar
IR receiver and sega glass interface circuit
I designed the circuit to make my Sega 3D glasses wireless, but system did
not work as well as I wanted it to work. I used the circuit below to receiving the
IR signals and controlling the IR glasses.
Component list
Amount Component
2 10 kohm resistor
2 22 kohm resistor
1 10 uF electrolytic capacitor
1 100 nF capacitor
1 10 nF capacitor
1 78L05 regulator (normal 7805 works also)
1 GP1U52X receiver module
3 1N4148 diode
1 2N2222 transistor (BC547 works also)
1 3.5 mm stereo jack
Modification ideas
The circuit can be also used for slow serial data transfer by connecting
RS-232 data output to the transmitter module left/right control pin and connect
the output of GP1U52X receiver module to RS-232 data input through suitable
RS-232 buffer circuit. Maximum data rates achievable are at around 1200-2400
bps speed.
Transmitter Electronics
The transmitter electronics
is built into each loco. It generates the pulses for the two IR LEDs that are mounted underneath the loco.
Schematic
Figure 1. IR transmitter schematic.
The components shown in the schematic are the
ones I use in the final design. They are chosen mainly because of their small
size. In my prototypes, I have used slightly different components, but this
does not have any effect on the function.
If you don't care about the size, you can
replace V1 with four standard diodes, e.g. 1N4148, and the transistors can be
replaced by some other types e.g. BC547B instead of BC847CW and BC557B instead
of BC857CW. You can also use a PIC12C508 instead of the PIC12C508A version.
Only the 'A' version comes in the smaller package (/SN package option).
Pulse generation
The pulse generation is done by the PIC
processor. The rest of the components are power supply and reset circuitry. The
transmitter sends out two different 8-bit codes, one for each LED. This makes
it possible to detect the direction of the loco. I let the codes differ only in
bit 7 and the parity bit. This gives a very simple PIC program.
Data is sent as 'LED off' pulses, where a '0'
or a '1' is coded by the length of the pulse. Each data sequence consists of:
- One parity pulse. (Odd number of '1's, including the parity bit.)
- Eight data pulses, least significant bit first.
The length of a '0' pulse is
38 PIC instructions, and a '1' is 102 instructions. The 'LED on' time between
each bit is 38 instructions, and the 'LED on' time between two consecutive data
sequences is at least 178 instructions. The PIC processor runs from its
internal RC oscillator, which gives a nominal instruction cycle time of 1
microsecond.
An example of a pulse
sequence with hexadecimal data 1A (decimal 26). High = LED on:
Figure 2. IR transmitter pulse sequence
example.
The PIC12C508A processor has to be programmed
with an individual code for each loco. The PIC program for the transmitter can
be found here:
- irsend2.asm Assembler source code.
- irsend2.hex Hex code, for e.g. IC-prog.
These files send the
hexadecimal data 0A and 8A (10 and 138 decimal). In the source code, the data
value to be sent is defined in the beginning of the program. Just change it to
the value you want for the moment. The program will send this value on one of
the LEDs, and the value + hex 80 on the other LED.
In the HEX file, you can change the value
with e.g. IC-prog. You find the value 0C0A at
hexadecimal address 100. The two least significant hex digits (0A) is the data
value.
Power supply and reset circuitry
The diode array V1 forms a rectifier bridge, that converts the incoming AC or digital signal to
DC. Resistor R1 is there to limit the peak current through the diodes to well
below the specified maximum value of 450 mA.
Capacitor C1 is the bulk decoupling capacitor. It must be rather large to
overcome the power drops that occur due to bad contact between the
wheels/pick-up shoe and the track. The bulk decoupling is placed before the
voltage regulation, because it is here you get the most effect out of it. But
this also means that you need to have a high voltage rating, at least 35 V.
R2, V2 and Q1 is the
voltage regulator. The function is equivalent of a standard 7805 regulator, but
the discrete solution is smaller, and probably also
cheaper. C2 is another decoupling capacitor, to filter out the switching noise
from the PIC.
R3, R4, R5 and Q2 is
the reset circuitry. When the voltage drops below a certain level
(approximately 2.8 V), the transistor Q2 turns off, and the resistor R5 will
pull the MCLR pin of the PIC down to 0. This will prevent a so-called
"brown-out condition", which otherwise may occur if the supply voltage
to the PIC drops below 2.5 V without going all the way down to zero.
The two resistors R6 and R7 are there to
limit the current to the two LEDs to a suitable
value.
Prototype
I have built two prototypes and mounted them
in two of my locos. Here is a picture of the prototype, mounted in a Märklin 3374. At the same time, I converted the 3374 to
fully regulated digital, with the 60901 conversion kit.
Figure 3. IR Transmitter prototype.
Final design
The final version of the transmitter
electronics is a 18.5 x 14 mm single-sided circuit
board. My friend and colleague Stefan Eskilsson
designed the layout. A PDF drawing of the layout can be found here.
I have assembled the transmitter boards, and
built them into most of my locos. The PIC processor is mounted first, together
with five temporary wires connected to the five
round soldering pads. The five wires are used
when programming the PIC, and are removed before the rest of the components are
mounted.
The square soldering pads to the left are the
connections for power and for the two IR LEDs.
Figure 4. Final IR transmitter board.
Serial port controlled infrared transmitter
with PIC
2002/06/16
designed by Peter JAKAB
This is a programmable infrared (remote control) transmitter, which can be
controlled from a PC serial port. It is capable of sending many remote control
formats, including the Philips RC-5 standard. Exact formats with the timing
parameter names are shown on the pictures:
operation
The controller will accept commands on the serial port. Settings are: 19200
bps, 8 bits, no parity, 1 stopbit, no flow control
(XON/XOFF or RTS/CTS). Commands consist of hex coded bytes and must be written
on the port as ASCII characters separated by space, terminated by ENTER (ASCII
char 0d) The list of commands is here:
|
SETSTATE |
set IR mod output state |
|
54 |
<state> |
|
|
|
|
SETPARAMS |
set coding parameters |
|
55 |
<ir_T>
<head_h> <head_l>
<bit0_h> <bit0_l> <bit1_h> <bit1_l> <tail_h> <tail_l> |
|
55 |
<ir_T>
<skipbits> <togglebits>
<firstbyte> <rc5tail> |
|
|
|
|
SENDPDM |
send ir
command |
|
56 |
<byte> [byte]
[byte] ... |
|
|
|
|
SENDRC5 |
send ir
command This command can be used to repeat a given ir
command, but not to transmit more commands one by one, because the toggle bit
is only set after sending out all the ir commands.
To send more than one ir commands, repeat the
SENDRC5 command with the appropriate second byte(s). |
|
57 |
<second byte>
[second byte] ... |
ir_T is given in 10 usecs, other timing values are given in ir_T
steps
You can use a terminal emulator program to test out the circuit (for example
minicom on linux, NC
terminal on DOS, or hyperterminal on windows), but
the settings usually won't work at first, so it is recommended that you write a
small program to set the parameters and send commands by pressing keys on the
keyboard.
Download source code here.
examples
To program the controller to send a "channel +" command to an ITT
3520 video recorder, you need to send:
55 38 10 8 1 1 1 3 1 1
This command will set these parameters: T=560 usec,
header pulse=16T, header gap=8T. bit0 pulse=1T, bit0
gap=1T, bit1 pulse=1T, bit1 gap=3T, tail pulse=1T
56 31 ce 01 fe
This command will send the required command bytes to the video recorder. You
can see that this format contains some type of ID and a command code. Each byte
is transmitted normally then with all bits reversed. You can repeat this second
command more times to ensure reception.
obtaining the protocol for your remote
The easiest is if you find the specification of your remote. Good pages to
start are: the
SIRCS page and the HP48
remote control program page. If you have no success, you need to measure
the signal timings yourself. If you don't have a storage oscilloscope, here is
a cheap trick: connect an IR
receiver module to your soundcard line input and digitize the modulation
waveform of all the buttons on your remote with a sound recorder and editor
program. Here is a waveform example for the ITT 3520 video recorder remote.
You can actually measure all the signal times of header, bit0, bit1 and the
tail pulse in a sound editor and decode the bits by hand. The yellow bars on
the picture show the decoded bits. The last 16 bits contain the button code.
The actual code calculated from the bits is "31 ce 01 fe", and will
control the video to step one channel up. Another example for the Panasonic
remotes POWER button digitized is here:
The encoding scheme is quite similar, with the difference being only in the
header/bit pulse/gap times. You can decrypt the command shown yourself. It
shows the sequence 02 20 90 00 3d ad, where the first 4 (!) bytes are the
device identifier and the last two (3d ad) are the actual command. These
remotes employ some strange checksum/code integrity mechanism, where the codes
are in byte pairs and the second byte is actually calculated (?) from the
preceding one or they contain more than 8 bits and mirror some of the bits.
schematic diagram
The first picture shows the controller and the IR transmitter parts. The
second shows the (nonstandard) serial interface level translator, which
converts the TTL voltages to/from RS232 levels of the serial port.
