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.

Building full HD IP Cam out of Raspberry PI

If you will start looking good for IP camera, you will see that they cost decent amount of cash. If you are looking to use one for your own needs like home security or office monitoring, then look around if you have spare Raspberry Pi and camera module. These things are cheap. Antoine likes to have control over things, so he started an Open Source project where he builds FULL HD (1080p) IP cam that can stream video at 30fps. It sends standard H.264 encoded video over RTSP protocol which is used in security applications.


As camera housing he used standard camera dome that can be found on eBay. To power the Raspberry, he implemented simplified PoE (Power Over Ethernet) on two twisted pairs from DC power adapter. The software part is based on Raspivid and Live555 RTSP Library. To get it working Antoine wrote step by step procedures that you need to follow in order to get it working. After some configurations made via WEB interface camera can be accessed through media player like Open VLC. Camera does not support night vision, but by adding NoIR sensor and IR light source, it can be possible. Also he plans of adding PIR detector to activate camera. Also he wants to enable recording of videos from web interface. So hopefully we will see some great updates.

Nixie calculator powered by Raspberry Pi

This is some nice calculator which is grate from all aspects. But probably coolest thing here that retro looking Nixie display and old style keyboard keys are fused with modern electronics such as Raspberry Pi.

Raspberry Pi is definitely an overkill for such calculator, but since these things are getting cheaper and cheaper, so why not? To use a bit more of Raspberry Pi power Scott made it internet connected calculator where you can send calculations to WolframAlpha. All parts of calculator is custom made where each nixie tube is controlled by K155D driver chip. Each chip is controlled through I2C IO expander that is connected to Raspberry Pi. Custom power supply board takes care of powering computer with 5V and tubes with high voltage. I’d say this is quite and effort to build a calculator.

Raspberry Pi model A+ had to come

Not long ago Raspberry Pi model B+ was announced. It had several great improvements in layout and GPIO. Other things like processor, RAM capacity remained same. So not long ago Raspberry Pi model A+ was announced and now you can get one for $20. As name implies, improvements are similar to model B+ just it remains without Ethernet and with less USB.


Among improvements we can see a micro SD card slot instead of SD. This gives more compact look and feel. Video and audio now are integrated in to single 3.5mm jack. GPIO port also was expanded from 26 to 40-pin header. Camera and display interfaces remain same. Also there are convenient mounting holes. Its dimensions shrunk to 65 x 56 mm. So if you don’t need Ethernet connectivity but still want Linux powered machine for battery powered projects, Raspberry Pi model A++ is a great choice.