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Topic: Auxiliary Dashboard for my wife's car (Read 2734 times) previous topic - next topic


Jun 20, 2012, 03:59 am Last Edit: Jun 20, 2012, 04:08 am by spirilis Reason: 1
I had a vision a little over a year ago to design an auxiliary dashboard to provide reliable time, compass heading & temperature info to my wife's car (which is otherwise rather spartan, being an ex-police cruiser we bought from a local dealer...) and I'm pleased to show off my progress--yesterday I ran the cabling and got the bulk of the system working and installed.

Pictures and details are here: http://spirilis.net/junk/arduino/carnet_install/project.html


  • Uses I2C and OneWire, with I2C being most of the communication

  • Makes use of a "long distance" buffered I2C network employing NXP P82B715 chips on each board to help the devices use the long-distance bus

  • LCD display is a large 16x2 by Newhaven, and I designed my own "I2C backpack" for the board which includes PWM on the LED backlight, ability to cut power to the LCD completely and go into deep sleep (SLEEP_MODE_PWR_DOWN).  The I2C commandset is built around a virtual 8-bit "memory map" implemented by a 256-byte char array on the LCD backpack's ATmega328 firmware, with the upper 16 bytes implemented as special "strobe registers" to carry out actions/configuration updates.

  • I incorporated a DS18B20 temp sensor into every board ... Because I can :) (and I have a ton of them)

  • ATmega328 used in the LCD backpack, ATmega1284P (Bobuino) currently used for the controller before I can build something permanent for that.  Arduino IDE used for both firmwares.

  • Future plans for this system include a Keyless entry system based on the nRF24L01+ and Sparkfun's nordic keyfobs.

Still need to run a cable under the hood/behind the bumper for proper ambient temperature, which is my next task before designing a control box w/rotary encoder for the dashboard.


Not bad. Probably the best looking home made board I can recall seeing. Might be time to step up to one of the budget professional options though.


Nicely done! You have put a lot of work and thought into that project for sure! The fact that you have your project in place and working is a great accomplishment!
Good links: Eagle tutorial= http://www.youtube.com/playlist?list=PLDE1858BD83D19C70
General Arduion tutorials = http://tronixstuff.wordpress.com


Jun 20, 2012, 03:20 pm Last Edit: Jun 20, 2012, 03:49 pm by spirilis Reason: 1
Humm, weird, went outside this morning and found it in key-off mode (as expected) but with the time 22 minutes slow.  I figured maybe the arduino crashed or something, so I disconnected & reconnected it and it updated--time advanced by 1 minute, but still 21 minutes slow.  I ran that system in my basement with the ChronoDot supplying the time for weeks without a hitch so I'm very curious what's gone wrong.  The ChronoDot (Maxim DS3231 breakout board w/ coin cell battery) is supposed to lose no more than 1 minute per year.

Alas, didn't have time to troubleshoot beyond that.  Will have to pick this up later in the evening.

On second thought, I think it's condensation.  I noticed lots of condensation on the rear window so it's a good likelihood there is condensation in the trunk.  Didn't even think about that when I designed everything.  The paint "soldermask" on the boards should help prevent some shorts, but I suspect I should stick a packet of dessicant in the sensor board housing or maybe apply paint to the pins of the DS3231 chip and exposed header solder joints to shore that up a bit more.  Better than trying to pot the whole thing...


Nicely done and the first time I've seen those I2C buffer chips used for real.

Rob Gray aka the GRAYnomad www.robgray.com


beautiful finished product, but I would leave the PCB laying on the dash it looks so nice  XD


Sorry, but I have to ask - Is your wife as thrilled with it as you are, or does she roll her eyes and shake her head over "that" project?


Haha, she likes it, but she wasn't half as excited about it as I was ;)
She keeps getting the urge to say "GO GO GADGET!" every time she steps in...


FWIW, suspecting condensation in the morning had something to do with the time lapse, I took the sensor board out last night and applied silicone dielectric tune-up grease to the SMD RTC chip's leads (the DS3231) and various other solder joints on the sensor board.  This morning the time was spot-on (with plenty of condensation all over the car, didn't check the trunk but it was probably there too.)

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