IR beam for the Catflap camera

In order to have enough light to take pictures of incoming cats I decided to make an IR beam. I wanted to go with IR because I don't want to have visible light on at home during the night. An IR beam will provide lots of IR light but produces hardly any visible light. A major drawback is that all colors are really off. The beam consists of a bunch of small low power 5mm IR leds. They have a forward voltage of about 1.5V and can source about 50mA of current. I also had some 1W LED driver modules I bought in China. These modules use the MC34063A in constant current mode. They don't have the best efficiency in the world, but they are rather cheap. Normally they are used in MR16 socket lamps.

IMG_20150126_214203.jpg (Twelve LEDs driven by a 1W driver) These drivers can put out about 300mA and expect a forward voltage of about 3V. They are designed for modern white LEDs. To use this module for the IR LEDs I had I had to put two LEDs in series and six of those pairs in parallel. Now I have 1W of IR LED.

IMG_20150126_220022.jpg (Completed unit)

I built two identical modules and built those two together in an electrical junction box I had lying around. The unit produces just enough to take pictures at night in complete darkness.

In the future I am going to make another module to help produce more light.

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