trying to build a multichannel rs232 volt ohm meter

Discussion in 'The Projects Forum' started by dicedaniels, Feb 15, 2010.

  1. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    im in the prosses of turning a cf-27 toughbook into an automotive scan tool. i have the software and the cable for the multiple scan tool software packages i am installing. that part is simple.

    BUT even with the multiple programs i am installing i still need atleist 6 inputs that monitor voltage and resistances for those certain vehicles that dont have a data link connector, or that are uncomatable with the software i have. plus for the vehicles that "are" compatible with the software, it could be used in cunjunction so that i can monitor what the ecu is seeing and what the sensor is actualy sending. this would out do the pro scan tools do to the user frendly interface of a pc.

    my question is what would be the simplest way to go about doing this?

    my options are:

    (1) buy multiple $10-$20 simple digital volt ohm meters, gut them and find a way to make the communicate with a rs232 or even usb interface with seperate channels.

    (2) start from scratch and build my own pcb and circuit.

    (3) spend over $1000 on a rs232 dvom module that has only one or two signal monitors. this would almost be useless to me looking at the fact that i only have $200 into the scan tool so far. id ductape 6 meters together befor i spent $1000. i dont even pay that much for the vehicles i drive.;)

    any ideas?
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    How about USB? Either way, there are many microprocessor circuits available online that will allow you to use the chip and a few components as a voltmeter while reporting the information back to a PC via rs-232 or USB


    [ed]
    This may be just what the doctor ordered. It is a 6 channel multimeter reporting on rs-232.
    http://sharon.esrac.ele.tue.nl/mirrors/zl1bpu/micro/SerialDVM/AVRDVM.htm
    [/ed]
     
    Last edited: Feb 15, 2010
  3. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    i dont even know you, but i think i love you!!!

    you just made my year!!!

    and its simple enough for my tired mind to figure out!!!!
     
  4. retched

    AAC Fanatic!

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    Aww, shucks. And valentines day was yesterday.
     
  5. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    somehow you hit and sunk the nail with one swing. the thing has a 5v output supply. this would be even more useful due to the fact that most of the three wire sensors on an engine use a 5 volt supply, ground and return. i could test a sensor outside the vehicle. we dont have a tool that does that


    THANK YOU!!!
     
  6. retched

    AAC Fanatic!

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    Well, weeks of training have prepared me for this moment.... my finest hour...

    :)

    Anyway, Im sure something will be wrong. If it needs any tweaking, let it be known.
     
  7. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    looks like the circuit in the link is drawn up for a 0-5v range, but at the bottom it shows how to modify it to take on a 0-16v range which would be perfect. im trying to put it together in my mind. i understand the circuit, but not computing the modification to give it a 16v tollerance. can you dumb it down for a mechanic. the two halves of my brain are fighting over it.
     
  8. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    never mind. i tried reading and learned something

    the top pic is right.
     
  9. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    the avr assembler download mentioned isnt quite as simple to find as worded

    i did find AVR Studio 4.18 SP1 which sounds right

    am i headed down the right path
     
  10. retched

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  11. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    what the heck is this about? trying to register.

    "What is the annual unit quantity usage?*"
     
  12. retched

    AAC Fanatic!

    Dec 5, 2009
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    How many of there chips are you going to use in a year?

    But you didnt need to register...This link will give you the file without registration:

    http://www.atmel.com/dyn/resources/prod_documents/AVRStudio4.18SP1.exe

    Im off to sleep. Hope this works out for you. If you need more help, there are a lot of people that know huge amounts. Or, Ill see what I can do in the morning.
     
    Last edited: Feb 16, 2010
  13. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    ok im back again with a new rookie question or 5.

    i take it the avr studio software included the isp software. i found the programming adapter Schematic. looks easy enough to duplicate. as you may have guessed, i am no electronic technitian. so i will be bugging you a little more than most.

    first, where can i buy one or two single chips? i see i need atleist one at90s4433 and one 74ls244. everywhere i look seems to deal in bulk and parts express doesnt show any on hand.

    second, is the executable software (AVRDVM.hex for 3.6864 MHz, DVM4MHZ.hex for 4.00 MHz) something i need to download, or is that also included in the avr studio?

    im set on building atleist 2 of these things. so i will absorb any advice i can get.

    im also wondering if there is an lcd version of this chip. im thinking of building a small portable dashboard with seperate back lit lcd displays. but then again, that would almost be too easy. i could probably just do as i mentioned before and gutt some of the $4-$5 dvoms off of ebay to accomplish that. so if there's not a chip available that wouldnt hurt my feelings any.
     
  14. retched

    AAC Fanatic!

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    Start with it this way. It will display the info into a window on the laptop you are using for the rest of the equipment scanning process. If later you want this device in a stand alone box, you can buy a GLCD or graphical LCD screen and have it display the data.

    As for the software, the software shown on the page is copyrighted. The author sells it for $10.

    I would recommend going that route rather than spending countless hours learning to program.

    I just sent you an email with how to get a hold of the author for the software you need.
     
  15. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    thank you. that makes life easier.:)

    im still interested in learning to write software, but not for something i need to trust so deeply. i work on alot of touchy cars with performance issues and i need this thing to be accurate. thanks again.
     
  16. retched

    AAC Fanatic!

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    You are welcome. When your ready, this will be pretty easy to switch to an lcd.
    The 6 output can be read by lcd drivers to display. But it will be nice to duct tape this box onto the laptop with your leads going to the car.
     
  17. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    http://robokitsworld.com/index.php?...ult&search_in_description=1&keyword=at90s4433

    would any of these programmers work for what im trying to do? they are specific to the chip. i dont know how much they want for the atmel version, but these prices are reasonable.

    duct tape is only good for sealing leaks on intake manifolds and radiators.;):D

    im building an aluminum housing that attaches to the body behind the monitor with machine screws. it will plug in, and bolt up like one large connector. the vga and other ports will have a pass through circuit so i can still use them. im making it large enough to fit the width of the laptop. this way i have room for other projects.

    i was also wondering if it wasnt just as simple as asking for a few chips pre flashed from atmel. that would speed things up a bit.
     
  18. retched

    AAC Fanatic!

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    You can get the preflashed chips. That would make things easier. and you could put off having to worry about buying a programmer or learning any coding.
     
  19. russ_hensel

    Well-Known Member

    Jan 11, 2009
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    Look at the arduino it is a avr enviroment with many of the decisions made for you in a reasonable way. It has 6 analog inputs and usb output.

    see: http://www.opencircuits.com/Microcontrollers_for_Beginners

    if you use some other environment do not get suckered into using asm. stick to a high level language. C is probably best for general use, Basic perhaps for beginners.
     
  20. dicedaniels

    Thread Starter New Member

    Feb 15, 2010
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    that would be perfect. where/how would i go about finding them? i could shrink the circuit down even smaller by loosing the flash port and extra components. not that they took up much more space. is there a part number i can just slip into partsexpress? or should i just contact him with the info i recieved earlier?

    this thing could almost be squeezed down to the size of a flash drive. thats nutts.

    is there a circuit out there for an rs232 ohm meter? i would only need 2 channels at the most.
     
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