Simple Infrared Control Extender Circuit Diagram
The opamp is followed by a BD240 after-burner transistor capable of supplying quite high current pulses through IR LEDs D2 and D3. However, the pulsed current through the LD274s should not exceed 100 mA or so, hence a fixed resistor is used in series with preset P1. D1 is an ordinary visible-light LED that flashes when an IR signal is received from the remote. With regard to the setting of P1, do not make the IRED current higher than necessary to reliably reach the final destination of the IR signal. Also, the currents mentioned above are peak levels due to the small duty factor of the IR pulses, the average current drawn from the battery will be much smaller. The directivity of the IR LEDs and consequently the range of the control extender may be increased by fitting the devices with reflective caps.
Author: Raj. K. Gorkhali - Copyright: Elektor Electronics July-August 2004