Battery Powered Infrared Remote Control Extender

  
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This is a battery powered IR Link which may be used in more than one room. The standby current is extremely low - so battery life is excellent. And by shutting down in the presence of extraneous IR radiation - it copes with the problem of excessive output current. This circuit is not powered directly from the battery. When a remote control signal
Battery Powered Infrared Remote Control Extender - schematic

is received - the energy stored in C2 - drives the emitter diode. At the same time - Q1 switches on briefly - and allows the battery to recharge C2. The green LED shows that the circuit is transmitting - and the yellow LED confirms that C2 has been topped-up. There is unwanted IR radiation in both daylight and tungsten lighting. To minimize its effect use an opaque housing and do not make the opening too large. (Try a horizontal slot measuring 2 cm X 1. 5 cm. ) Shade the receiver diodes by mounting them side-by-side a few centimetres deep - inside the case. The depth of shading required will depend on the lighting conditions. (Try 5 cm to start with). To reduce the effects of visible light - use receiver diodes with a built-in daylight filter ( Maplin CY91Y). Or cover the opening using a small piece of dark transparent plastic. Part of the display panel from a scrap VCR is ideal. Position the unit out of direct light and avoid reflective surfaces. If all else fails, adjust VR1 to reduce sensitivity. What you are aiming for is to ensure that in standby mode Q2 remains switched off so that C2 retains its charge. If unwanted radiation does reach the receiver it will not result in a large output current. C2 simply discharges and the circuit shuts down. When the source of the unwanted radiation is removed the unit may be reset by interrupting the power supply for a few seconds or by pushing the (optional) reset button. If you do...



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