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

Radio spectrum FFT on Atmega8

This experimental project developed by ChaN. He managed to analyze Radiosignal spectrum and calculate its FFT which is displayed on graphical LCD. When analysing RF frequencies there are some problems with speed. Even when analysing 1MHz radio signal there is over 4000 samples needed for correct ADC.   To solve this problem he managed to shift carrier frequency to lover by using generic method: Frequency conversion, which operates with signals as complex, where operations with negative frequencies are available. So if signal is 100MHz with span ±1MHz, then frequency is shifted to 0MHz±1MHz. This way by Nyquist they there is enough to sample signal at 2MHz. In circuit diagram (PCB (top) and PCB (bottom) )there is seen how this conversion is performed with couple mixer circuits SA612A and reference frequency of 455kHz. Atmega8 program samples converted signal, calculates FFT and draws pattern on LCD with refresh rate of 60 times per second. See movie how it works. Continue reading

Interfacing Nokia 6100 color LCD to AVR controller

Thomas Pfeifer have connected Nokia 6100 132×132 pixel 4096 color LCD to AVR microcontroller. LCD is also used in Nokia 6100, 7200, 6610, 7250 and 6220. He connected LCD to Atmega8 microcontroller:   As there are two types of displays: with Epson chipset(S1D15G10) and Philips(PCF8833), he wrote code for Philips chipset. Firmware is written in AVR-GCC language where image can be uploaded via serial cable. Also there are few videos view sample video on how it works AVR-3D-Engine. Continue reading

Amateur ECG monitoring device

This is very simple ECG monitorin device with no protection and isolation circuitry. Also signal quality isn’t good enough to interpret data seriously. But circuit works and shows ECG pattern.   Signal is amplified and filtered via Analog devices instrumental amplifier AD620. Signal then is sampled with Atmega8 ADC and sent to LabView via USART. Refik didn’t include the whole circuit, just amplifier module, but it is not hard to recreate microcontroller part as there are standard connections to ADC and USART. Program is written in assembly language where ADC reads data and sends it via USART. Continue reading

Programmable DC pover supply

This is must have tool in you LAB. The idea was to build microcontroller based DC power supply witch was easy to build and was cheaper than in market.   Device was built by using only standard components. Device is capable to provide up to 30V 2A. Power supply unit can be controlled by PC using i2ctalk program which can be run under Linux, Windows, Mac OS X and Solaris. Software can be found here. Dont forget to check for an updates. You can order this power supply unit as a kit from Tuxgraphics online shop. Kit includes additional documentations and circuit diagram. Continue reading

AVR DDS waveform generator

This AVR DDS generator can generate signals from 1Hz up to 65535Hz. Thanks to well known DDS algorithm frequency limits can be much higher, but signal resolution drops in higher frequencies. Current range is enough for most of audio signal equipment testing. DDS algorithm is written in software where Atmega8 runs at maximum 16MHz. There are several signal waveforms available: sine, square, sawtooth, triangle and reverse sawtooth and pseudo-random noise.   Signals are stored in lookup tables as DDS algorithm requires. Signal output is organized via simple R-2R ladder DAC. LCD signal goes through shift register, this way only 3 MCU pins are used, while other serves for other purposes – buttons, other outputs. Project is well documented PCB and source files included. Author states that he will build another DDS generator with improved control and variable signal amplifier at the output.   Continue reading

Movement tracker with accelerometer

This device so called Station Master is small key ring sized device which tracks movement in the train. As train goes, device vibrates, but when train stops, it generates alarm after predefined number of stops. So you don’t miss your station. Device is based on Atiny13 microcontroller and MMA7260 3 axis accelerometer from Freescale. Alarm is generated by cell phone vibro motor.   Project files include schematic and assembly program which is very compact due to smart program optimisation – especially filter part, where movement signal is detected from noise pattern. Continue reading