Instructables
Picture of 1990 Mustang GT Info Center
*** UPDATE: v3.6 includes fixes to time and RTC time to display before GPS signal lock ***

*** NEXT: hook up and calibrate the outside temp sensor ***

This Arduino project uses a 20x4 LCD I installed in place of my stock speedometer to display useful information similar to this:

▀▀█ ▀▀█       12:34am
█▀▀ ▀▀█ 12.3v    NNE
█▄▄ ▄▄█ 200°F   86°F
123,456mi    Trip:123.4

-  The speed, time, and heading are all updated by the GPS module.
-  The battery voltage is taken directly from the car battery using a voltage divider to convert 0-15VDC in to 0-5VDC out.
-  The engine temperature is calculated from a 0-5VDC input from the stock ECT (engine coolant temperature) sensor. This information is also used to cycle the electric cooling fan on at 200 deg F and off at 190 deg F using a 5V coil relay controlling a heavy-duty solenoid under the hood.
-  The outside temperature is taken from a DS18B20 serial temp probe mounted at the front of the vehicle behind the bumper cover.
-  The odometer and tripmeter values are stored in the (NV)RAM of an RTC module. A momentary pushbutton reset switch is mounted in the stock location to reset the trip meter.

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Portions of this program were copied from or inspired by the following:

Big LCD number font:
Hifiduino
http://hifiduino.blogspot.com/

Overall program structure and odometer/tripmeter coding:
Kurt Schulz' Scooterputer
http://www.janspace.com/b2evolution/arduino.php/2010/06/26/scooterputer

Tom Torfs' 8 bit converter macro:
http://bytes.com/topic/c/answers/216333-binary-constant-macros

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Hardware:

Arduino UNO R3
http://www.amazon.com/Arduino-UNO-board-DIP-ATmega328P/dp/B006H06TVG

SainSmart GPS Module
http://www.amazon.com/SainSmart-Aircraft-Controller-Mega2560-Duemilanove/dp/B009YDK6NA

Antenna GPS 3V Magnetic Mount SMA
http://www.sparkfun.com/products/464

Seeed STR104B2P Protoshield
http://www.radioshack.com/product/index.jsp?productId=13297702

SainSmart 4-Channel 5V Relay Module
http://www.amazon.com/SainSmart-4-Channel-Relay-Module-Arduino/dp/B0057OC5O8

Real-time Clock (RTC)
http://www.amazon.com/Real-time-Clock-RTC-for-Arduino/dp/B00ATRD4OS
elijaht125 days ago

What screen did you use?

TankMorph (author)  elijaht125 days ago
http://www.amazon.com/gp/aw/d/B003B22UR0?cache=41a68074ef29a278a09bde58d0b71949&pi=SY200_QL40&qid=1408918053&sr=8-2#ref=mp_s_a_1_2