Turn-key PCB assembly services in prototype quantities or low-volume to mid-volume production runs

Using real tachometer to display CPU usage

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. Continue reading

Motor based gauge is a great way to replace a display

If you are looking for ideas how to make your project catchy, consider using different way of presenting data. Instead of using LCD, LED displays go with analog gauge. You can use analog meters for that, which use may be a bit complicated as it needs analog voltage. In digital electronics we want it to be digital controllable. TheRengineer suggests using stepper motor driven gauge. It is based on X27.168 stepper motor which has a needle attached to its shaft. It can be easily driven with Arduino or other micro. It is mounted on convenient breakout board with 6 pin connection header. Of course the library is here for instant use. He’s done really good job making it move smooth and fast. Continue reading