h. It is really easy to add an illumination sensor to a K8055 or a K8055N board!

Illumination measurement is one of the common home automation problems. There are only two things that have to be done to measure illumination through one or the K8055 or K8055N analog channels. The boards already include 2 operation amplifiers, one for each analog channel. The original Velleman assembly manual for K8055 or K8055N kit mentions resistor spaces (R53 and R54 on K8055N board and spaces R8 and R9 on K8055 board), which should intentionally be left empty. They are intended for custom projects where a higher input amplification is needed on A/D channels. This is exactly what is needed for illumination measurement with a fototransistor (ex. Siemens SFH 300). Connect a 10 k ohm trimmer in place of R53 on K8055N or R8 on K8055 to use A/D channel 1. Or connect the 10 k trimmer in place of R54 on K8055N or R9 on K8055 to use A/D channel 2. Then connect fototransistor collector to +5 V by soldering a wire to a spare jumper (see photo) and connection the jumper to +5 V pin on the control board. Connect the emitter pin of the fototransistor to the desired A/D input the board. Next, adjust the 10 k ohm trimmer to get appropriate A/D response according to the minimum and maximum illumination span.

There is also an alternative! Even if you decide not to add 10 k trimmer, there is still enough gain for SFH 300 fototransistor to get maximum A/D output value of around 500 (on the scale of 0 ... 1023) with 10-bit A/D conversion. However, if you still use 8-bit A/D conversion (and original Velleman firmware) you would only achieve the maximum response of around 32 (on the scale of 0 … 255).