Category Archives: Electronics

Temperature/Humidity Logger

Recently, a need arose to take humidity readings of a crawlspace, over an extended period of time. An Arduino clone called the Bare Bones Board (BBB) is used in this project, mainly for its ability to be mounted to a breadboard.

Using a commercial-off-the-shelf sensor and microSD card, the logger takes temperature and humidity readings at a predefined time interval and writes the readings to a text file on the card. An Octave/MATLAB script is shown that plots the results.

All source code can be found on GitHub.

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Analog Sensor Calibration

Using a simple mathematical formula, it is possible to calibrate analog sensor readings. If you are using a COTS analog sensor, and have access to a high quality, or more reliable sensor, taking several readings can provide a coefficient and offset for calibration.

In this example, a voltage sensor is implemented with a voltage divider. A digital multimeter is used to glean more accurate readings, and a coefficient/offset is generated with Octave/MATLAB.

All source code can be found on GitHub.

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Arduino Mega 2560 R3, ICSP Programming and Bootloader Reload using AVRDUDE

Using an off-board programming tool, it’s possible to program the Arduino Mega 2560 directly through the ICSP pins.

I have a Sparkfun Pocket AVR Programmer at my desk, but according to their documentation as of 04.12.2015, the ATmega2560 is unsupported. Pololu has an inexpensive USB AVR Programmer that is up to task.

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Indoor Car Stereo

I’ve never previously had a stereo/speaker problem, for the past seven years I’ve had two iterations of Logitech’s Subwoofer/4+ Speaker combination. One set is currently with my Brother at school, the other set is 3500 miles away in Virginia.

I’ve been in California for the last seven months, thumping along with the laptop speakers. Not bad, tinny, can’t get too loud, can’t rock a party, but okay. This project started when my office-mate came in to work with brand new speakers from some store bought system that he didn’t need.

When I lived in D.C. I used to have an old Cobra C.B. radio strapped to a throw-out computer power supply, so getting a stereo together was the natural response to receiving these speakers. Continue reading