Standard digital cameras can register images of narrow range of spectra. Normally this is visible light and some of IR area. If you need more specific characteristics, then price of such cameras grows exponentially. Hobbyists always try to find cheap solutions in order to get desired results. One of them is to use single pixel camera which simply scans through all image and then combines it in to picture. Single pixel is nothing more than photo-diode which can be sensitive to different wavelengths. Artyom have built a simple prototype of single pixel camera where sensitive photodiode is moved to scan all image.
The idea lies in to building dark box with tiny hole in it. Image passing through that hole can be projected on the opposite plane. In order to get better image resolution he had to test various photodiodes. They have to be small size to give more resolution, but bigger sensors give less noise. This single pixel camera is universal tool. For instance if you need to register images in infrared spectra, then use IR photo diode. Visible light sensor is great for taking BW images. And if you need other properties, then put a sensor of your choice. The only downside is speed – process is really slow.
Membrane keypad is a great input device where you need protection from moist. If you look around you will find that many toys have them. Kitchen, bathroom appliances also may have such buttons. In many areas membrane keypads are replaced by capacitive buttons. Membrane switches are still mechanical device which can wear our or break. If you would like to experiment with membrane switches and probably build something with it, then check out Paul‘s guide on how to build one by yourself.
He used a copper foil tape to make a conductive layers of keypad. He designed keypad and its inner layouts with Adobe illustrator. He stacked a 4×4 keypad and connected it to Arduino to give a test. This is perfect for non intense input devices and you can design your own layout and labeling.
Thermal imaging devices are still too expensive for non commercial use. But this doesn’t mean that those images can’t be interesting to play with on a hobby level. You could use this for inspecting electronics hots spots, detecting low temperature resistance areas around the house and do other crazy things. Andrew got a chance to play with Flir Lepton thermal imaging sensor, so he have written a driver to make it useful. Sensor has 80×60 resolution with 14bpp. This may seem low, but having in mind that each pixel detect temperature level, then it is more than enough to get useful data.
He’s chosen an STM32F4 processor on a Nucleo board. The he attached Gameduino 2 which features FT800 graphical processor with fairly large LCD on top. Sensor module communicates over SPI interfaces (there is an option for I2C). In order to extend images for full screen on LCD, he used interpolation methods like simplest “Nearest neighbor”. For better results he suggests using more advanced methods like Bilinear/Linear/Sinc interpolations.
Numitron tubes are special type of displays, where digits are constructed out of segments like in 7-segment LED displays. They can be driven with standard 74HC595 shift registers. Numitron indicators require about 20mA of current so interfacing them to microcontrollers is fairly easy. Kalshagar have built really nice four Numitron digits based digital clock.
He wanted clock to be modular so that different parts could be reused in other projects if needed. To do so, he split design in to two boards – a display board which carries only tubes and driving circuit; while another part where microcontroller, RTC and backup battery is. He has done several versions of board and enclosure while eventually he stayed with rusty metal casing which looks really great.