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

Network activity monitor on Atmega328p

Every time something is going on with network you simply log in to your router to get more details. For instance Zak constantly found this annoying to check if someone is chewing the download speed. So he decided to build a network monitor which displays network activity. Monitor is based on ATmega328p microcontroller which listens for incoming data packets using Bluetooth module. Debian Linux based PC Router simply runs shell script which takes necessary parameters, forms packet and sends over Bluetooth. Network monitor is equipped with 1.8” graphical LCD where all information is displayed. This include download and upload speeds, ping, lost packets, email notifications, ADSL parameters and history graph of Down/Up. Also he added a V-USB support so monitor could fetch local computer data and display information like CPU load and memory usage. It is still work in progress so we expect more updates on this.   Continue reading

LED icicle could decorate your Christmas

LED icicle is an ornament made of ATmega8515 microcontroller and 26 blue LEDs. All LEDs are connected to separate I/O pins. Eight of them are driven by microcontroller while other 18 through NPN transistors. Microcontroller simply drives each LED with pseudo-random brightness level that gradually changes with different speed. This give effect of iridescent shine. LEDs are housed in fur-tree toys – plastic icicle and half of plastic ball as stand. Continue reading

Measuring internal resistance of LiPo

Lithium Polymer batteries loos its capacity during exploitation. Significant aging starts to be visible after 100-200 charge cycles. If you are using these batteries long enough it is worth checking if they are still useable and maybe you need to think about new ones. For instance in RC plane bad batteries may be result of crash. One method of discovering battery age is to measure internal resistance of cells. With some variations new battery has about 5mΩ which increases up to 20mΩ at the end of life. These figures may be different depending on battery specs. Anyway the problem is to measure the internal resistance. Bleuer suggests his circuit which is capable of measuring 2 to 8 cell LiPo battery. Measuring is done by passing current through 1Ω load resistor and then voltage of cell is taken. We all know that there is a voltage drop on resistor when current flows. When we know the current and voltage we can calculate the resistance. Several experiments and fine tuning allowed reach pretty good results. Measuring is controlled and taken using ATmega8… Continue reading

Posting radiation data online

Radiation is one of dangers you can’t notice. If you live in risky area you might want to have a radiation meter near by. Radu Motisan has been working on online remote radiation monitoring station. The idea is to monitor environment for radiation constantly and post data to web charts. Radiation is measured using sensitive SBM-19 Geiger Muller tube. Design is based on Atmega168 microcontroller and ENC28J60 Ethernet chip. Plotting only radiation value seemed not very interesting so he added more sensors to monitor other parameters like temperature. Actually there are several temperature sensors used – DS1820 and DHT-11 along with humidity sensor. Ambient light is measures using luminosity sensor and pressure with barometer which comes with third temperature sensor. So there is a bunch of data continuously floating in to website in real time. Continue reading

Customizing longboard with LED POV

If you want to mod something – best choice is using LEDs. Rotating LED POV displays are one of cool ways to use them. Ch00ftech had some experience with building POV displays, so he decided to do something nice to his longboard. Longboard has 72mm diameter wheels so electronics need to be tight enough to fit in. Attiny24 microcontroller seemed to be just enough for this task. 14 pins obviously isn’t enough, so this is done using multiplexing. Image synchronization is done using IR LED sensor with fixed reflector, which orientation can be altered to rotate image. In order to make PCB balanced he placed a coin cell battery to the center of PCB, so it would have no effect on ride. PCB design was another concern, because there are many types of longboard wheels. The idea of selling these started looking not so much attractive. But on his wheels it works perfect. Continue reading

Interfacing MMC, SD and SDHC to AVR microcontrollers

In many microcontroller projects you run in to limited memory problems. Usually you get enough Flash for storing program code, but when talking about storing data – it runs out quickly. Think of data loggers or music players. Fastest and most accessible way of increasing memory is using SD (MMC, SDHC) cards. They are popular, cheap and can be connected to computer. Roland Riegel has been working library that allows interfacing memory cards to AVR microcontrollers. So far it supports MMC, SD, SDHC cards with partition table and can read/write FAT16/32 formatted cards. It is easy to connect cards to AVR. If it’s powered using 3.3V then connect lines directly to SPI, when voltage is 5V then simple voltage dividers lowers signals to required 3.3V. Depending on how card is formatted you may need different flash size microcontrollers like in order to support FAT32 you will need at least Atmega328. Roland performed several benchmark tests on reading and writing so you could judge the efficiency of code. Continue reading