Are you feeling tired of paying large electric bills? Probably you feel that some tweaking in home electric system would save couple bucks. So why not to try, but for this you will probably need a power level monitor to determine where are biggest usage of electric. Building power level monitor can be quite easy – there can any microcontroller be used for this. In this case a LPC2138 ARM7 microcontroller has been chosen which, I think, probably is too powerful for such simple task.

The simple idea of design is to sense current and step down voltage to level acceptable to MCU IO ports. The current sensor is made of transformer with some modifications. Device detects zero crossings of voltage and current in order to determine the phase shifts so it could calculate power RMS correctly. Power level information can be viewed in two ways – via 7 segment LED indicator mounted directly on device or it can be sent via USART to monitor it computer screen and probably so some statistics. The full project can be downloaded here.

When dealing with signals probably the best way is to leave the task for DSP processor as they are optimized to do DSP calculations like FFT, filtering and other digital signal manipulation. But not always a DSP processor is an only solution especially if you want a low cost and non critical performance application like audio spectrum analyzer. In this project an ARM7 (LPC2138) microcontroller is used to do a FFT algorithm.

The tricky part about FFT on such microcontrollers is dealing with complex numbers that are also real. The project description shows whole process how these problems are solved. Project is set up on ZL6ARM prototype board, which is equipped with all necessary peripherals like LCD, MAX232 converter. Program is developed under ARM-GCC compiler. Audio signal is sampled by LPC2138 internal ADC with sampling frequency of 40 kHz. FFT algorithm calculates the chunks of 256 samples and produces the graphs on PC screen. This is a great project and nice tutorial to get in to DSP world.

Most of the time, we’re have been experiencing this awful situation before. Go figure, how many times you’ve tried to adjust something for level with a spanner, but you’re not able to see how you doing!

Furthermore, things start to out of control, if you are handling a pool table that has four adjustable feet, which you can fiddling around with the spanner and trying to figure out what is the exact table level is! Yeah, the whole scene could turn into a really nasty and huge pain for the fixer…

However, there’s better solution for the above matter. Let’s meet the Mr. Incredible, Dual-Axis Level Sensor (Oops, is it really a person?).

Basically, the dual-axis level sensor is based on LPC2138 microcontroller. Even though the designation is quite simple and unattractive, but it provides exceptional convenience to the users!

For your information, the sensor system is fully-designed around electrolytic tilt sensors, where is capable of providing precise positioning measurements in within a few seconds!

The units form the basis for many other applications. The Dual-axis level sensor is including with self-leveling platform, builder level, pinball, pool table leveling and other industrial applications. Hence, it’s suitable for being used, not only at home but in the industry sectors as well!

ARM microcontrollers are great for running embedded linux. This project got some power as it uses 2MB SRAM, Philips LPC22xx processor that runs at 60MHz, SD/MMC card slot, NIC 10Mbit RTL8019 Ethernet chip.

If you dare to recreate this project – here are Eagle files needed. Also you need to load uClinux in to RAM memory with bootloader and uClinux source code with proper MMC/SD and network card drivers. Once everything is set – you can run various linux based servers like http, smtp etc. and access them via your computer client programs like browsers, pop clients – you name it.

ARM microcontrollers are 32 bit systems with high potential. It is enough power to run small operation systems like uClinux. The only limitation is that operations systems require much more program memory than internal chip memory can provide. Ulrich Radig used a NXP LPC2294 ARM7 microcontroller which carries 256K of internal Flash memory which is enough to place a boot-loader which loads uClinux kernel to SRAM.

It interesting how he solved low memory problem. SD card was split in to two partitions where one partition FAT16 was used to store kernel which has to be loaded to memory, second is Linux (ext2) partiion for custom use. To support this he has written a simple driver. When Linux is loaded, it is easy to run various custom programs like web servers, and so on.