Simple home automation solutions can make your life easier. In other hand too much automation can be annoying. So there is always a middle between benefit and annoying. This is why there are so many attempts to build automation that differ from project to project. Johannes has been working on his version of home automater called “botman”. It is based on Arduino with Ethernet connection.
“Botman” is capable of doing several things like measuring indoor temperature, humidity and barometric pressure (BMP085, DHT11). Then pull weather data from server via weather API. Also he though that he needs public transportation info which is also pulled from server. Indoor climate conditions is constantly archived in to Google Spreadsheet. And finally, to complete home automation concept, there is a Android API which allows controlling home appliances remotely. Home automater is placed in laser cut enclosure which also serves as front panel with laser cut engravings. Servo motor needle indicates weather conditions while other data is visible on LCD. Three push buttons are used to navigate the menu and select information.
Very often analog gauges are used to measure some rate parameters. In most cases they are based on voltmeters where needle position is driven with PWM signal. Pat found a tachometer from old car lying around and decided to use it for displaying something useful – CPU usage. He starter building this project on Raspberry where tachometer would display its CPU usage.
First of all he had to figure out the signals needed to drive tachometer from 0 to full scale. He found a table with frequencies and PWM values on Tekronix 3252 information site. Then another issue was the signal level. Tachometer needs 5V to drive it while Raspberry Pi signal level is 3.3V, he used 7404 buffer to bring that level. The rest is Python code running on Raspberry Pi, which reads CPU value and then sends driving signal on pin 11.
tronixstuff have written a great tutorial how to interface and program real time clocks (RTC). As an example he took two widely used chips DS1307 and DS3231. The main difference between both modules is clocking mechanism that can result in precision. Usually they come in modules that can be easily connected to microcontroller board via I2C interface.
Both modules come with built in pull-up resistor, so there are only two wires required to interface to microcontroller (plus power lines). Simple demo program allows to output time and date infromation to serial terminal window every seconds. Both modules come with backup batteries so if you diconnect them from Arduino board they will continue counting time. When next time you connect them again, you will get correct time values.
Most of Nixie clock designs end up with at least four indicators that display time at once. More Nixie indicators require more space and power. But pinomelan decided that single digit IN-12 Nixie indicator is more than enough for building small portable digital clock.
He put small PCB with PIC16F84A which drives single Nixie with discrete transistor. Nixie tube needs high voltage to light up, so he used HV supply from disposable camera. Clock displays time by periodically flashing all digits in series. During display each digit can be set up by pressing button at the right moment. Nixie clock along with battery could fit in to 35mm cube enclosure if needed.