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car instrumentation

Discussion in 'Electronic Basics' started by Kamus of Kadizhar, Dec 30, 2003.

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  1. I'm toying with building an instrument panel for my car.

    Basically, a LCD display about 6" x 1.5" which would show things like oil
    temp/oil pressure, coolant temp, tranny temp, battery voltage (and
    possibly draw with the use of an appropriate shunt), outside air temp,

    I would guess that someone out there has done something like this. I
    figure I need something like a very basic CPU, output of some sort to
    drive the LCD (serial? video?), and a mess of A/D converters. Or perhaps
    some other way of doing this?

    I'm not looking for a full package like the race cars use, just something
    better than the idiot lights on my car, something useful with a high
    'cool' factor.

    Any links, ideas, comments welcome.


  2. JeB

    JeB Guest

    Probably just one A>D on your cpu ... then a method to switch between
    sensors. The sensors to work with it are probably the challenge. The cpu
    probably already has display drivers.
    I don't understand why no one is manufacturing something like this.
    There are bicycle computers in the $10-20US range that can do everything
    but take out the garbage. A single display with the ability to select a
    given input or simply scan all sensors would be fine. I'd like the
    basics: oil pressure, coolant temp, voltage, but being able to add the
    other "wish list" items above later would be good and a source of
    further income for the manufacturer.

    - jim
  3. Well, the idea is to display all the things you want to monitor, then,
    on alarm conditions, zoom in on the out-of-range items and light a
    single idiot light on the dash.

    The sensors are out there; basic high-quality resistance-type sending
    units are around $10 for temp, pressure, etc. Once you get into gear
    shift indicators, air-fuel mix, etc. that runs into money.... I figure
    a basic voltage divider using the run-of-the-mill senders should work.
    Amen. It's so simple, that I don't know why someone hasn't done it.
    You could couple it with a GPS (you'd have enough CPU horsepower left
  4. JeB

    JeB Guest

    I'd put this in the philosophical difference category ... I'd be happy
    with a single display and as mentioned, scan thru them as an option. And
    I'd probably want something audio if a real alarm condition existed.
    However, re-using a dash idiot light is not a bad idea.

    where do you find these?
    i'm certain there are special purpose "embedded" cpu that have onboard
    A>D, display drivers, etc.

    I'm sure there are others.
    Where? I can't find any - except for industrial ones that cost $$$$.

    Any pointers? I don't know enough about PC/104 stuff but that seems to
    be the way to go. Still, it's damn near $1,000 for the computer, CPU,
    A/D card, and senders..... Cheaper than a blown engine, but..... Plus
    all of the programming....

    There's some stuff I can adapt, but still....

  6. JeB

    JeB Guest

    well beyond the $10 a pop range but at least they do exist.

    ok ... i opened my mouth (er keyboard) without a specific device in
    mind. Some googling and my first find in this category is:

    Motorola Flash MCU with advanced LCD driver architecture

    The 68HC908LJ12 MCU features 12K bytes of on-chip Flash memory as well
    as the following

    Liquid Crystal Display Driver capability for direct connection to a LCD
    panel; 26 frontplane x 4 backplane configuration; 27 frontplane x 3
    backplane configuration; 27 frontplane x 1 backplane configuration;
    software programmable LCD contrast control Real Time Clock Module
    second, minute, hour, day, day of week, month, year counters; automatic
    calendar with leap year adjustment;

    100 Hz chronograph counter; alarm, and UART; Serial Peripheral
    Interface; 10-Bit Analog-to-Digital Converter six (6) channels; 32 MHz
    phase-locked loop

    2002 news release suggests $4 each in large quantity.
    this would likely be a very time consuming and expensive project as a
    "one off". But you'd learn a lot, if inclined (or not ... a pretty
    serious project including software) .
  7. Hah!

    And the development kit is $99.... Sounds like this might do the trick
    - it's about the same price range as individual gauges....

    C-programmable to boot. Anyone have any experience with these? Any
    other, similar one-board computers out there?

    Now to find a decent LCD display cheap....

  8. JeB

    JeB Guest

    I'm sure there are dozens to choose from.
    The mag "Nuts'n'Volts" has or used to have a lot of advertisers in this
    area. I think they have an online presence too. Probably a newsgroup on
    embedded apps too.

    I believe the Motorola unit could do the job and the 68xx series has
    been around a long time so lots of development tools.

    or u might want some sort of laptop type display if you want lots of
    data viewable at the same time and u can find a suitable driver system.
  9. ross

    ross Guest

    I don't know what type vehicle you are working with
    but I am trying the same thing with a 88 Camaro
    My plan uses the aldl connector of the ecm computer
    I currently have two 486 75 mhz laptops (compaq)
    that have been repackaged into a new dash display

    Most sensors are already hooked up to the ecm
    and can be displayed on a pc

    currently car has mechanical problems so project is on hold
    until I get it running again
  10. Several years ago "Radio Electronics" or "Electronics Now" magazine had a
    several part series on building your only digital dash for your car. If
    anyone is interested I can scan the articles and post them somewhere.

  11. OK, any ideas on where to find a ready-made controller with this as the
    CPU? I've fished around google, and pretty much all I find is press
    releases and marketing blurbs...

  12. Josh K.

    Josh K. Guest

    Unless I didn't see it... If your car was made in 96 or later (after 2000 in
    EU) you have a diagnostic port. it works on one for 3 transmission types.
    many people have kits, free online blueprints or sell assembled kits for
    interfacing from car diag ports to serial ports. you'll have to do some
    checking as to what your car supports but most support pressure, oxygen
    sensors, temps and the like. Easiest and cleanest thing might just be to
    use a small embedded PC or old laptop tucked away and just link your serial
    through one of these small kits to the diag port. so Instead of being
    invasive to the car's CAN network or anything just ask the computer in your

    It will tell you what you want to know. and if you ever get weird values
    you can also use that info to troubleshoot your car for a failed sensor or
    something is genuinely wrong! also you don't have to modify all those hard
    to find plastic parts. I've seen entire kits with free software for under
    $175! cables included. check them out...

    -Josh K.
  13. Josh:

    That was how this started. The problem is size, power, cost, and time.

    A PC104 chassis with a 386 CPU will run about $1000, with all the A/D
    stuff that I would need (the CAN network doesn't provide info like oil
    temp, oil pressure, etc.) Add to that the cost of the diag port to
    RS232 kit, Windows, and an LCD display, and you're bumping up against
    the $2K mark.

    I just don't have the room for a laptop or a large display - I already
    have all sorts of real estate taken up with other stuff (a 15" TV, a 5"
    backup camera, a computer that plays movies, CB....)

    Not only that, but now I have a PC that takes time to boot, and that
    draws significant power (so I can't leave it on.) And that has a hard
    drive that can fail (I just lost a RAID array over the new year's

    So my choice is a tiny embedded MCU with a 4x20 LCD display. I figure I
    can get two of those, with the sensors, for under $300, including the
    development kit. The only thing I won't get is a tach - a $20 MCU just
    doesn't have the horsepower to keep up with a tach. So add $130 for a
    state of the art tach if I want one. Still a lot less than a PC104 chassis.

    Add to that that the MCU only draws 6ma - not not 5-6 amps like a
    laptop. So I can leave it on at all times.... And there's no boot up time.

    Sure, I have to do my own programming, but that's the fun part :)
  14. Having read some of the other replies, and believing I understand what you
    are trying to do, would you consider using an already available digital
    dash if one was made for your car?

    I admit to not having read all the posts indepth, but I don't see you
    saying what kind of car you have. Judging by the CB, 15" tv, 5" backup
    monitor, etc. etc. etc., I'm almost inclined to believe you're driving a
    conversion van <g>

    Still, for many vehicles, digital dashes were simple direct-swap
    replacements, and you can probably pick one up at a good junkyard for
    anywhere from $15 to $50, depending on the yard.

    Just a thought. I know it wouldn't be homemade, but it would do most if
    not all of what you are wanting to do. Only thing is that the odometer
    won't be the same, but it should still work, and there's no need for bulky
    interfacing or reprogramming of computer equipment.

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