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Matlab program to montior the motor performance

  1. Jul 22, 2006 #1
    I am considering writing a matlab program to montior the motor performance of my model airplane. I would have to do it through USB, because I only have one 232 port, so I cant use multiple devices from that one port.

    I would like to montior the temperature, voltage, current, power, static thrust and rpm.

    Then I can make matlab plot the info.

    Does anyone know where I could find some CHEAP! instruments to do this?

    I think this might be too expensive to actually do though....
     
  2. jcsd
  3. Jul 22, 2006 #2
    I bought a USB interface not long ago, it takes analog and digital inputs. I bought it in Kit form and soldered it up myself.

    This one from CPC is similar

    Im not sure where you could get one in your neck of the woods.

     
  4. Jul 22, 2006 #3

    FredGarvin

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    Define cheap. DAQ would be a lot cheaper if you were just going for temp. Power would be a calculated value. You wouldn't necessarily measure it directly.
     
  5. Jul 22, 2006 #4
    Under 300 bucks for the whole shibang.
     
  6. Jul 23, 2006 #5

    Bystander

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    Under $300? Snoop around the "used" and "rental" joints --- you can find some very good deals on discontinued models of what are otherwise very good instruments. Keithley, HP, Tek, Philips, the whole "high-priced" legion at nickels and dimes on the "new" dollar. Thought I still had the link handy, but McAfee's "monkey" seems to have flattened it --- google "used laboratory equipment (or instruments, or multimeter, or scanning multimeter)," you'll find some pretty shady looking hits, some people who are very proud of their inventories, and some decent deals.

    KUSB 3108 goes for around $1k, lower resolution models around $500 --- you might look 'em over --- shipping time stinks, or did --- "just in time business model" far as I can tell. U. S. nationals only --- "sensitive technology" restrictions apply.
     
  7. Jul 24, 2006 #6

    FredGarvin

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    You could look into something like Omega's Nomad line. You don't want something with telemetry because that will cost more and add a transmitter.
    http://www.omega.com/ppt/pptsc.asp?ref=OM-40&Nav=dase01

    The thing I am wondering is how much weight are you going to be adding? To get thrust, you'll need at least a strain gauge which will require power and conditioning. That may hinder you.
     
  8. Jul 26, 2006 #7
    This is for a trust stand. It wont be in the model. I found one place that has data logging sensors, but not what I need. I gota call for the price. Remember, I want something that has USB. I want to dump it into matlab, if possible. The problem with the Ammeter I found is that it wont do 30+ Amps that I need.

    *If* I can find all the things I need, I would probably need to buy a Laptop on my workbench. Arg, I guess this is going to be about ~1k in total. I hope not, but if it is, so be it.
     
    Last edited: Jul 26, 2006
  9. Jul 26, 2006 #8

    Bystander

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    Run down to Radio Shack, or whatever your favorite "toy store" happens to be, and pick up the appropriate shunt resistors.
     
  10. Jul 26, 2006 #9

    NoTime

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    A few feet of copper wire can make a reasonable high current shunt.
    It's cheap.
    You don't have to buy an ammeter.
    A volt meter will work fine here.
     
  11. Jul 27, 2006 #10

    chroot

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    Forget the ready-made data acquisition products -- they're going to be too expensive for your budget.

    Get a Cypress EZ-USB microcontroller -- they're easy to program and cost about $7 a piece. They make interfacing with a PC via USB a snap.

    Next, get some moderate-speed serial analog to digital converters, like the AD7476 from ADI. You can very easily connect these to your microcontroller, and they're only a buck or two each.

    You should be able to find some basic temperature sensors, etc. from any decent distributor like DigiKey.

    You're going to spend more to have a printed circuit board fabricated than you will on the components.

    - Warren
     
  12. Jul 27, 2006 #11

    chroot

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    BTW, I have boatloads of experience with the devices I mentioned, and can give you any help you want/need with them.

    - Warren
     
  13. Jul 27, 2006 #12

    FredGarvin

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    Just spitballing here...

    There is one other option...You could go old school and handwrite results. Are you planning on doing transient measurements or steady state? With the few measurements you're talking about, it wouldn't be that hard. You would only have to worry about displaying your instrumentation instead of also interfacing with the computer. That occurred to me yesterday as I was walking by one of our old manometer banks.

    You could also see if your department has a strip chart recorder available. We have models that accept 6 inputs. They're nice for looking at transients.
     
  14. Jul 27, 2006 #13
    I just want to make a simple stand where I can hook up the motor, prop, battery and speed controlled and run it. That way I can vary the throttle setting, and have a log of what the current was over time, what the temperature was, what thrust the propeller makes, what RPM is the motor producing? This is not necessary, but I would find it interesting to know.

    I do not want to record by hand, that is archaic and pointless when I can do so much more with Matlab.

    Chroot, your offer is generous, thank you. I will take it into consideration. I am not an EE or a programmer, so the though of making it myself from the basics is a bit unnerving. :yikes:
     
  15. Jul 27, 2006 #14

    chroot

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    Ah, well, using an off-the-shelf data acquisition module would be the easiest route, but they suffer from major price inflation. For some reason, a couple of 1990's through-hole components soldered to a two-layer board goes for $300 on the open market as a "hobbyist DAQ module"..... but you can construct a USB 2.0 (400 Mbps) interface to a couple of almost theoretically perfect > 1 MSPS A/Ds for the price of a meal at McDonalds. I suppose it's just supply and demand at work.

    Hmmm... maybe I should get into business making super high-speed high-capability hobbyist modules......

    - Warren
     
  16. Jul 27, 2006 #15
    I found everything I need!

    It's going to total to about 800 bucks though! AHHH!

    Oh well. I'll post more details later.
     
  17. Jul 27, 2006 #16
    did you not look at that usb interface board? Is that not enough?
     
  18. Jul 27, 2006 #17
    Here is what I found from this company. http://www.cometsystem.cz/english/

    I just got off the phone with their US distributor. Nice, knowledgeable guy.

    The parts that he has that I can use are:

    • Dual Channel V/I metter (I will have to step down the V/I through a network myself and then step it back up in matlab) Price$355
    • Four channel Data Logger- (2,temperature, 2, other) $365.00
    • Optical RPM measurement sensor $69
    • 2 usb adapters $100
    • 2 2-m temperature probes $70
    • Power supply for the RPM measurement sensor $5.00
    • Total price $964

    But I can buy it in pieces, so I might try the V/I sensor first, and work from there. The data comes in a good format for using matlab too.

    Code (Text):

    ýrobní èíslo:  01910443
    Test

                                Teplota        Vlhkost        Ros.bod
                                   [°C]            [%]           [°C]

    3.3.2003 14:07:00              23.5           11.5           -7.3
    3.3.2003 14:08:00              22.7           11.7           -7.6
    3.3.2003 14:09:00              22.5           11.7           -7.7
    3.3.2003 14:10:00              22.3           11.7           -7.9
    3.3.2003 14:11:00              22.3           11.6           -7.9
     
    Last edited: Jul 27, 2006
  19. Jul 27, 2006 #18

    chroot

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    Jesus H. Christ, that's highway robbery.

    - Warren
     
  20. Jul 27, 2006 #19
    :rofl: your telling me!
     
  21. Jul 27, 2006 #20

    chroot

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    Those modules probably contain < $10 of components, and probably took a contracted EE less than a week to design.

    - Warren
     
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