Hi. I'm new to this microcontroller stuff, and haven't done much in the way of programming other than a couple of simple programs for a graphing calculator years ago. However, when it comes to automotive, there isn't much I can't do...
Which is why I want to replace my 25-year old analog instrument cluster with a nice new set of LED gauges. First off, I KNOW someone is going to suggest an LCD display. My dash has 4 gauge holes with six gauges in it (2 large for tach and speedometer and 2 small in each of the other holes) that are approximately 4" in diameter (US English here, don't need or want metric), and I don't have room for a reasonably sized LCD display, plus I would need something to fill the other 3 holes. Yes, I know there are prefab gauges out there, but none for my application. I'm looking for a combination of 7-segment displays and single LEDs that act as a bar graph, similar to the analog gauges.
I have been researching this for a couple of years now, and purchased a couple "books" with schematics for a decent set of gauges. The only problem, however, is that there are what seems to be WAY too many chips involved. I'm trying to keep my costs as small as possible, because anything over about $4-500, and I might as well get the pre-fab universal gauge set and trim it to fit in my stock cluster housing. Not to mention I would like to run an LED odometer, 7 digits, and the schematics in the books provide for a power loss of 10 days. Which doesn't help if I want to take the car off the road and disconnect the battery for 6 months. I have done a couple of searches, and found something called the "Multidisplay", built by a member here. Problem with that is that it's run using an LCD, for one, and doesn't include all of the gauges I'd like to see, for 2.
My current gauges are as follows:
8-18 VDC voltmeter, would like to have a 10-LED bar graph and a 3-digit (volts, tenths, and decimal) LED
Coolant temp, running off a 0-5 VDC sender, maximum of 260F (something like 130C), would like to see same as above and also for 0-120*F intake/inlet air temperature, no decimal needed
10 LED Fuel gauge and also a 10 LED Intake Vacuum gauge running off of a Motorola MPX4250APX pressure sensor (no boost), which, I believe, has a 0-5 VDC output, or a stock sensor that DOES have a 0-5 VDC output
0-70 PSI engine oil pressure gauge, sender also has a range of 0-5 VDC
The large gauges, I would like to see about 20-30 LEDs in the bar graph ring and 4 digit LED displays:
0-6500 or 7000 RPM tachometer, 3 reference pulses per revolution on a V6, currently have a tachometer system, and looking for more accuracy than a 3-digit gauge
0-150 MPH speedometer AND 7-digit odometer, possibly with selectable/resettable trip odometer if possible (the EEPROM is why I'm curious about the Arduino so I can have a non-resettable odometer). I do not have a cable speedometer, mine runs off of a 2000 pulses per mile sending unit assembly...
I've been looking at any number of solutions to satisfy my curiosity, including a Maxim ICL series driver chip for the tach, the MAX 7221 for the odometer and possibly other gauges, and a document I found through Google that describes a speedometer with odometer for a motorcycle BUT uses an LCD instead of an LED display, complete with schematic (but I decided there has to be a different way with fewer parts, right?). I'm hoping an Arduino or similar is the answer to my problem... If it's possible, I'll work the hardware end first and then deal with the coding later as the car isn't going anywhere for a while (being completely rebuilt after being completely stripped down). And yes, I do plan on retaining the factory odometer in a hidden spot to keep the government happy...