Daniel Pozzi - Argentina
This Mark3 version of the Infra Red extender is a special version designed to control appliances that use high frequency modulated IR remote controls.
IR appliances use pulses (control signals) sent over a modulated IR carrier wave. The carrier wave may be modulated at
various frequencies, 36-38KHz being the most popular.Some Satellite receivers use even higher frequencies than this.
The IR1 remote module receives an infra red signal and separates control pulses from the modulation. To re-transmit,
a 555 timer is configured as an astable oscillator. The 555 timer is controlled by the signal on the reset pin, high
generating a carrier and low no carrier. Each control pulse turns on the oscillator for the duration of a logic high
signal and off for a logic 0 signal, thereby creating a newly modulated IR signal. The IR module, part number IR1 is
available from Harrison Electronics in the UK, IR1 may not be listed in their catalogue but if you ask
for an IR1, they will send you the correct part. The IR1 arrives in a small aluminium case, the connections viewed from underneath are shown below:
Infra Red Module, IR1 Pinout
Harrison Electronics have limited supplies of the IR1 but as a replcement a standard IR module like the TSOP1838 may be used. The pinout is shown below:
The carrier frequency is determined by R1 and C3, values shown work at 39.7 kHz, but these may be altered to provide different carrier
frequencies. The final CMOS 4049 invertor ensures that under "no signal" conditions both LED's are also off.
C1 100u 10V
C2 100n polyester
C3 120p silver mica
C4 100n polyester
R4 47R 1W
IC3 IR1 module from Harrison Electronics
IC4 4049 CMOS Invertor
LED1 Red LED (or any visible colour)
LED2 TIL38 or part YH70M from Maplin Electronics
Pinouts for the IC's can be found on my IC pinout page, click here
PCB Layout (courtesy of Claudio from Italy):
First the component side of the board is shown below.
And now thw pcb itself.
The Mark 3 circuit is an improvement over the Mark 1 and 2 circuits, however the drive from Q1 inverts the polarity of the output pulse. In some cases this can cause problems so the output stage is rewired as an emitter follower. This is the basis for the Mark 4 circuit. If you still have problems then I would recommend trying the Mark 4 circuit
Last Revision 21-4-04