In the few free moments I could spend the last week I made some progress with the Arduino. Bought a whole kit with an Arduino UNO, breadboard, wires and all and mounted it on a…..breadboard!
My son’s Windows 7 installation was so slow in compiling sketches that I wiped it and installed Linux Mint. He wasn’t pleased with it in the beginning, but he likes it better and better now. He played with some LEDs, but I tried to get some sensors going. The thermistor was quite easy and after looking at some code and getting the appropriate libraries the 1-Wire temperature sensor put some temperatures on the serial monitor. That gave me hope because my 1-Wire weather station is getting old and Maxim has phased out some essential ICs to keep it running. A new station based on Arduino boards could be a great alternative.
So I dug out a spare HIH-4020 humidity sensor and getting that to work was also trivial. Next was a photo diode and the one on hand was the SFH203P. The current produced by that sensor is so tiny that it can hardly be measured by the analogue input on the Arduino. The answer is to use an op amp, but the only one I could find in my junk box were some UA741s. They are special to me, because I used these to build some projects together with my father when I was young, so they must be at least 30 years old. But they require a bipolar voltage rail and can’t even work rail-to-rail. I tried them anyway, using a unipolar voltage supply, but no dice.
I had some other op amps lying around, but they were all surface mounted devices and I couldn’t find the matching break out boards. Guess I will have to find some through hole versions, like the TLC271CP which sell for a buck a piece here in Taiwan. Can’t go wrong with those for that price, I guess.