This is a device that can capture the IR signal from most remote controls and send the information via serial port to a computer for display. It provides all the vital information such as on/off durations, pulse counts, and carrier frequency. The captured information can be use to aid development of microcontoller code to respond to or transmit IR codes.
This circuit makes use of LEDs for more that just an indicator. They are also used as a voltage regulator and as an IR detector.
Step 1: Parts and Schematic
Blue LED with Vf of 3.0 to 3.3
Green LED with Vf of 2.0 to 2.2 (not ultra-green or true-green)
Red LED with Vf of 1.8 to 2.0
Infrared LED with wavelength of 940 or 950 nm
1N4148 or similar diode
100 nF (0.1 uF) capacitor
Microchip PIC 12F629 microcontroller
Female DE9 connector
Wire (solid core 20 awg)
PIC Programmer (PicKit 2 or similar)
Step 2: Power Supply
The power supply uses two LEDs as a shunt regulator. The low current of the circuit and the current limit of the serial port make the use of a simple shunt regulator practical for this application.
Begin assembly by soldering three short solid core 20 awg wires to pins 2, 5 and 7 of a female DE9 connector. This is the only soldering required.
Insert the wires in to the breadboard as show. The wires for pins 5 and 2 must be in adjacent columns. The wire for pin 7 should be several columns to the left.
Install the blue LED with the cathode connected to the wire from pin 5 of the DE9 connector.
Install the green LED with the cathode connected to the anode of the blue LED.
Install the 1N4148 diode with the cathode connected to the anode of the green LED and the anode connected to the wire from pin 7 of the DE9 connector.
The power supply circuit is now complete.
To test the power supply, connect a USB to serial converter to the DE9 connector and use terminal software (Hyperterminal or similar) to open the COM port. The RTS line will switch to a positive voltage and the LEDs should light up. Measure the voltage to confirm it is close to 5 volts. Disconnect the serial cable and proceed to the next step.
Step 3: Microcontroller
Program the PIC12F629 microcontroller with the attached code. Make sure the oscillator calibration value is preserved.
Install the PIC in the breadboard as shown. Pin 8 must be in the same column as the wire from pin 5 of the DE9. Pin 7 must be in the same column as the wire from pin 2 of the DE9.
Install a short jumper wire from the cathode of the 1N4148 diode to pin 1 of the PIC.
Install a 100 nF capacitor across pins 1 and 8 of the PIC.
Step 4: Activity Indicator and IR Sensor
Install a red LED with the cathode to the junction of the blue and green LEDs, and the anode to pin 6 of the PIC. This LED will indicate that IR is being received from the remote control.
Install an infrared LED with the anode connected to ground and the cathode to pin 5 of the PIC. This LED is used as a IR detector rather that an emitter. It is reversed biased by a pull-up resistor in the PIC to enable operation in the photoconductive mode.
Assembly is now complete.
Step 5: Usage
Run the IR Scope software from http://www.compendiumarcana.com/irwidget (bottom of the page). Select the correct COM port, and press the capture button. When the blue and green LED light up, press the button on the remote control that you want to capture. The red LED will flicker to indicate that IR is being detected. It is very important to alight the IR LED of the remote with the IR LED of the capture circuit because of the poor sensitivity of an LED used as a detector.