Water Level Logger – efficient 3.3V supply

Posted on 2014/03/09 by andy

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 noticeable voltage drops. While size is not a concern, it is not a smartphone, simplicity and cost (again) is a factor. Looking for optimum took me couple iterations. Continue reading →

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Water Level Logger – solar charger

Posted on 2014/02/17 by andy

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 to go. Until I read article on Linear’s LT3652 all-in-one chip. Continue reading →

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FreeRTOS tickless idle on Atmega128

Posted on 2014/01/23 by andy

m128-zzzReal-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. Problem is that while FreeRTOS supports low-power mode it does not provide such implementation for AVR. So I have implemented porting layer on my own. Continue reading →

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Water Level Logger – overview

Posted on 2014/01/13 by andy

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 firmware, local file system and couple different local and remote buses and protocols. All that within the rigor of power and cost efficiency. Let’s take a look at the latter first.

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iGO out of memory – solved

Posted on 2014/01/09 by andy

igo-memory-erroriGO Primo navigation software surprised me right at the moment I needed it badly. As always I forgot to upload maps, etc, before travel, so, as usual, I did it at the hotel googling for solution. Visiting Singapore was not different, this time though after uploading extra content iGO choked with “Out of memory. Requested 1701978227 Cache: 0” error. Rolling changes back did not help either. An hour struggle and I caught offender red handed.  Continue reading →

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Singapore, a week later

Posted on 2013/12/23 by andy
Singapore

After disappointing first day, remaining part of my staying was more graceful, once or two times a day showers, humid and hot hazy weather for most of the time. Few evenings free of work and half of next weekend I could dedicate to see what is going on in this state-city. Continue reading →

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Singapore, day one

Posted on 2013/12/08 by andy

I should call it Singa-pour, the whole sky is gray, skyscrapers tops are hidden in clouds and the wall of rain outside keeps the same pace for last couple hours. At day zero, which was yesterday night when I arrived, it was hot and humid but surfaces were dry with no marks of water. This morning was still dry, hazy but sun light trying to reach pedestrian’s faces. I even started regretting I have left my skate boots at home. Continue reading →

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Water Level Transmitter – surge protection

Posted on 2013/11/20 by andy

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 production-grade devices leads to financial impact: loss of hardware, maintenance time and penalties from SLA breaches. Continue reading →

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Water Level Transmitter – RS-485

Posted on 2013/11/05 by andy

Serial transmission over long line was the last stage of first iteration in prototyping. Local communication between microcontroller’s USART and PC was already working with MODBUS thus adding RS-485 driver and couple passive elements meant to be piece of cake. Murphy’s law got me down as I should have expected. Continue reading →

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Water Level Transmitter – microcontroller

Posted on 2013/10/18 by andy

Once the signal from sensor is converted in ADC it has to be processed and delivered to remote master unit. Having extra local measurements sources, like temperature, it has to be combined altogether. Multiple transmitters coexisting on single line (bus) to master unit complicate protocol of data exchange. A microcontroller (MCU) is most flexible way to make it all happen. Continue reading →

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