Category Archives: Electronics

SIM900A fixed for Europe

So you got SIM900A, cheaper version of SIM900 with the same pinout/functions and 2-band instead of 4-band GSM radio, just to stumble on logging to network. While its great for Asian GSM infrastructure in different places in the world you … Continue reading

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3D printing at home

These days turning imagination into reality at home is more real than ever. RepRap movement made fused deposition modeling technology affordable. Turning a figurine or mathematical object into physical object is exciting and funny and using 3D printer to fabricate … Continue reading

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PCB from Chinese factory

Working prototype device made of modular PCBs let me go for the next step. Learning the process of professional PCB production in factory and making short series to scale out number of devices in the field. I had to get … Continue reading

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Water Level Logger – insufficient RAM

For prototype I estimated that 128kB or flash would suffice and I was right; firmware took 75kB even though fatten up by embedded strings used across the code for tracing. On the other hand 4kB RAM of Atmega128 turned to … Continue reading

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Water Level Logger – voltage level conversion

Digital subsystems with different supply voltages have to align their logical states if they want to talk to each other. It can be done with variety of discreet components as well as dedicated integrated circuits. It is simple task these … Continue reading

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Water Level Logger – efficient 3.3V supply

Problem is simple: 3.3V DC/DC converter has to work with high input voltage (>20V), has to be highly efficient as it works continuously in energy scarce conditions, and has to provide up to 300mA dealing with SD card bursts without … Continue reading

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Water Level Logger – solar charger

It was my first work on photo-voltaic and rechargeable batteries technology. I have read a lot about mono- and poly-crystalline cells, tracking the highest efficiency points of panels (MPPT) or proper charging/discharging. Facing that I felt I have long way … Continue reading

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FreeRTOS tickless idle on Atmega128

Real-time operating system (RTOS) makes embedded coding more elegant and maintainable if MCU has to take care of many things at the same time. FreeRTOS also supports many platform including  8-bit AVRs. I am using it because of both reasons. … Continue reading

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Water Level Logger – overview

The logger part of Water Level Station experiment was second in line for design and development. The transmitter measuring water level was done first and turned to be just a warm-up comparing to logger feature list: self-powered unit with multitasking … Continue reading

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Water Level Transmitter – surge protection

Thunderbolt that hits near a long cable line can induce spike of hundred of volts. Budgetary RS-485 driver will not protect circuitry from damages caused by over-voltage and over-current. While scorched prototyped device makes constructor sad, failure to bunch of … Continue reading

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