e-snowflake revisited


Four years ago I made microcontrolled snowflake decor using home made PCB based on toner-transfer process. I got back to this idea late in 2015 to make short batch for family and friends. Second version was about fixing design issues and adding extra features: rechargable battery, USB interface and automatic brightness regulation. Nice looking factory-made PCBs were ready in November 2015. Continue reading

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3D printed rain gauge

2nd version design

Water level monitoring on river basin under observation was completed mid 2015. From rainfall-rainoff modelling perspective rainfall capturing was missing. Low budget, 3d printer at home and some spare time pushed me to design my own rain gauge. Before autumn rains all required stations received tipping bucket pluviometers upgrade. Continue reading

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Outdoor device? Bundle up your PCB.

coat-wet-simWinter is coming… actually it has already come bringing constructor’s nightmare. Sudden freezing cold caused unexpected and massive restarts of all field stations. All because of the same hardware reason. Reason impossible to happen. All that because circuit boards were not suited up for real harsh outdoor conditions. Continue reading

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Bitten by dead FTDI chips


Counterfeit chips have always been on the market. Most of the time stories were told about fake high-end components like computer GPUs. I did not worry and over last couple years I bought hundreds genuine chips from China. They were always low-cost components and always worked as in specs. Until now.  Continue reading

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Toner transferred PCBs

16. removing toner

Thanks to Chinese providers printed circuit board fabrication has never been so cheap. With PCB comparison tool it is also darn easy to choose from. Sometimes though old’ye home made PCB is what you are looking for. So I made a photostory from my one-hour creation process for newbies. Continue reading

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Kicad upgrade: push & shove and freerouting revisited


Kicad PCB toolset changed a lot over last two years. Great contribution from CERN is merged with stable release on one hand, new library format and projects migration necessity on the other. Meantime Freerouter cooperative tool disappeared and my reluctance to move was justified. Until recently when I gave migration a try. Continue reading

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EMI shielding

First 3D printed shielding

Close GSM antenna proximity to bare PCB was troublesome latching microSD. Using most resilient flash cards nearly solved the problem. Extra shielding would help to prepare for worst field conditions like area of weakest GSM signal leading to highest emission and EMI. I took long and tough lesson to get shielding done right. Continue reading

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OSX mishandles SSID with @ sign

Lately at the airport so-called user-friendly Apple operating system  was stubbornly failing to log into WiFi without giving me any clues. Meanwhile Android phone was happily sucking data from the same hotspot. It turned to be an OSX (Yosemite 10.10.4) bug when hotspot uses valid for SSID “at” (@) sign. Intuintion of engineer let me quickly overrun this issue. But hey Apple, what about average Joe OSX is designed for? Continue reading

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GSM antenna freezes microSD


Dealing with RF is tricky part of electronic design, even though I never had significant issues with GSM in my prototypes. Advancing in WLS project however I discovered a nasty issue with micro SD prone to lock up on interference from GSM built-in antenna, even located in significant distance. To my surprise half of different tested brands suffered from it. Thru extra tests, selection and SD replacement action I was able to greatly improve stability of long-running system.
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External RAM and lost MCUCSR


Atmega’s MCUCSR status register gives info about restart reason like regular reset-pin shorted, watchdog initiated reset, or brown-out on low voltage from power supply. Pieces of valuable information for device defect tracking. Reading MCUCSR early in test program was fine, while in real system with bootloader and external RAM memory I always got incorrect value. It took me couple hours to pin down the problem of single incorrect byte of information. Continue reading

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