*** 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.

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

Big LCD number font:

Overall program structure and odometer/tripmeter coding:
Kurt Schulz' Scooterputer

Tom Torfs' 8 bit converter macro:


Arduino UNO R3

SainSmart GPS Module

Antenna GPS 3V Magnetic Mount SMA

Seeed STR104B2P Protoshield

SainSmart 4-Channel 5V Relay Module

Real-time Clock (RTC)
<p>Hi, can you please provide specific libraries that you used? I use IDE 1.6.7 and i have errors in the compilation. Excuse my Google English .</p><p>Thanks Jiř&iacute;</p>
<p>I am currently working on a digital instrument cluster for my 1993 Mustang GT. I will be using 3 Arduinos with 3 4D Systems 3.2&quot; screens. I am using GPS for the speedo but have noticed that the speed only updates once a second. This makes the needle jump around instead of a more fluid movement. I need to see if its the screen refresh that is causing this or the GPS data. Its still a work in progess, I'll make a post once complete.</p>
<p>The 93 Mustang GT that I am making a digital instrument cluster.</p>
That's ridiculously awesome. I love it! Unfortunately, the GPS modules pretty much all update once/sec. I'm no programmer (obviously), but the only way to smooth out the display is through programming. I never bothered since I was just looking for functional. Sorry I can't really help. My old 90 GT is just sitting in the driveway now, waiting for a new home. It will be a long time before I can drive a stick again since I was in a motorcycle crash last November. My leg bones are almost completely metal now.
<p>What screen did you use?</p>

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