Carduino Half-way Done (well, just the display)

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The main reason I haven’t posted in about a week, was that the complexities of the Carduino project made it harder for me to start building the project. I got the GPS working with the TinyGPS library, but I ran out of ram (again), so I considered (again) if I should rewrite it to make it fit. It was bogging me down I decided that I didn’t need that feature (it was on the nice-to-have list anyways).

The next thing that bogged me down was attempting to determine how much protection I would need to protect it against transients on the battery lines. There are chips out there that you can use, TVS, but ultimately I decided to just use protection diodes, like here. I’m also not only using a reverse blocking diode, but a zener diode to handle transients above 15V (the regulator only takes up to 16V, MCP1703-3302E). I have no idea if this will protect it adequately, but I’m not afraid of taking risks.

The last thing that bogged me down was trying to figure out how to sleep non-essential circuitry. My plan was to use a N-channel mosfet to do it, but when I did a very rudimentary test (physically disconnecting ground from display board), the LED’s still remained lit, and even changed. Apparently the two shift registers got enough low voltage from the control pins. When I tried it on the wireless module, reconnecting it reset the board, not good. So I’m going to use a switch to turn it off and on.

Cue story about Russians using pencils in space, whereas NASA redesigned a ink pin for millions. IF I want to improve on it, I can add any of these features, but for a first revision board, this does the job, and does it well.

A quick explanation on the display board. It requires 6 lines for now, and I will use ethernet cable to connect it to the Carduino. It will be placed near my instrument panel, and it is tuned so the brightness at night time won’t blind me (hopefully). It has two shift registers (74HC595) which control an 8 segment BCD display (single bcd digit with decimal point), and 8 LED’s. The Carduino will quickly cycle through the various readings (4 temp, 1 voltage, 1 ?) and display it’s level, as well as a number associated with it. If any over-temperature event occurs, it will sound an alarm using a Piezo speaker. It will also light up the decimal point, so i can quickly see if any reading is abnormal.

Tomorrow I’ll wire up the main board for the Carduino. Putting it in my car will be a fun challenge as well.

Coming up i’ll be starting a new project, a Garden automated with Arduino (controlling watering, lighting, and more). A quick update for the Controller 2.0 project, I received two different wireless nunchuck’s, and both of them work flawlessly with it 🙂

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