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Multiplexing project

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by mrn, Apr 6, 2013.

  1. mrn

    mrn New Member

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    This may present a problem though, so what your saying is to have a driver chip after the shift registers?
     
  2. throbscottle

    throbscottle Well-Known Member

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    Yes. Without attempting to actually design something I'd suggest having an AC supply common to all the coils, and switch it to each one with a mosfet switch perhaps. You can probably get then in an array.

    But before going into details like that you should try winding a little coil, sit a little aluminium disc on it and apply AC to the coil and see what happens, see if it's is any better than a plain old solenoid...
     
  3. mrn

    mrn New Member

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    I will try this, where can I get a AC source though? (ill just google that) :)
     
  4. dave

    Dave New Member

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  5. throbscottle

    throbscottle Well-Known Member

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    An electronic lighting transformer will get you 12VAC at about 400Hz, I believe. I've seen them on eBay for about £1. Again, don't take my word for it, check for yourself! For such a low power requirement as you have I would think you could safely drop the output voltage with resistors.

    If you don't want to do that, you could build a little inverter - it's quite easy to do - if you have a look on Roman Black's website he has some nice designs - you would just have to modify one a bit so you can draw AC rather than using the DC output.
     
  6. mrn

    mrn New Member

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    I sorta realized how hard and money eating it would be to have thousands of tiny coils, so im trying to think of another way to do this, some way of pushing out little droplets.
     
  7. blueroomelectronics

    blueroomelectronics Well-Known Member

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    Driving 128 of anything will add costs up fast. What is this thing for?
     
  8. mrn

    mrn New Member

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    right.
     
  9. mrn

    mrn New Member

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    does anyone know how fast nichrome wire can be heated and cooled? can it be done atleast 120 times a minute? or twice a second. getting hot enough to push a drop of water like a bubble jet ink head?
     
  10. throbscottle

    throbscottle Well-Known Member

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    It depends how much current you can push through it, what temperature you want to achieve, how efficient your drop dispersal method is, and how effective your cooling method is. Your question is not far short of "how long is a piece of string". I would guess you can do that though, it doesn't sound extreme.
     
  11. mrn

    mrn New Member

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    i just needed to know based purly on the wire itself how fast it heats up with a 5 v 1 amp supply and how fast it will cool while submurged in the water?
     
  12. blueroomelectronics

    blueroomelectronics Well-Known Member

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    Sounds like you're going to have to build a prototype and experiment.
     
  13. throbscottle

    throbscottle Well-Known Member

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    I think the manufacturers should be able to supply that kind of info - there should be data sheets for the wire. In general, thinner wire will heat/cool quicker than thick wire because it has less thermal inertia. You should be able to dig around on the internet to find the maths for this - way out of my depth, just trying to give some pointers :)
     
  14. mrn

    mrn New Member

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    @throb: okay i will look.

    my other idea is kind of a weird one but what if I had to tiny contact points (pos and neg) that are touching and when are supplied power create a spark and heat?

    I tried it with my handy 5v 1amp psu and it the two wires actually heated up pretty quickly, however i don't know if this would cause some problems with other circuitry.

    I experimented further and found that a piece of metal can, touching a bit of non conductive(weak conducting) wire creates a very nice kind of glowing spark very quickly and very hot.



    does anybody know exactaly what it its that bubble jet heads use for a heating source? is it just a tiny sliver of nichrome wire or? Ive looked and looked but I cant find anything.
     
    Last edited: Jun 30, 2013
  15. throbscottle

    throbscottle Well-Known Member

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    Any kind of contacts that create a spark and heat will wear out fairly quickly because metal ions will migrate from one electrode to the other. Only other problem you might encounter is noise. Also they won't work the same in liquid

    Apparently the heating element in printers is a resistor. It's probably made out of something very expensive...

    For what you want you could try using tiny smd chip resistors mounted in your delivery tube somehow. Drive them to maybe 2x their rated power at first, then see what you need to adjust it to. That way you can use volts to get the power rather than relying on high current.

    Don't forget, your liquid will act as a cooling agent so you have to experiment with it in situ, not just test in free air.

    This might be interesting:
    http://mimech.com/printers/inkjet-printer-technology.asp
    http://cpn.canon-europe.com/content/education/infobank/printers/bubble_jet_technology.do
     
  16. mrn

    mrn New Member

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    aw that makes sense.

    how fast will the sparking metal ware out?




    i see those smd resistors all over the place, the question is how to get one off of a old chip??? :) good idea though i will try and desauder one of them


    what about a tiny sliver of nichrome wire?
     
  17. throbscottle

    throbscottle Well-Known Member

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    I desolder smd's in bulk using a heat gun and a knife! Sort them out afterwards. Desoldering just one is quite tricky without special tools - I made a soldering iron bit with two prongs especially for the job, but you can buy them. A bit with a long straight edge might do it too.

    No idea about the nichrome - you would have to try it. You are still talking about a very low resistance though, it's specified as ohms per metre. So lots of current.
     
  18. mrn

    mrn New Member

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    i'm surprised the heat gun doesnt damage things? i guess soldering is just as hot or hotter.

    would the resistors operate under fluid?
    also which is which i know some of the tiny parts are actually capacitors, how do I tell the difference? are the resistors only the ones with numbers on them?
     
  19. Pommie

    Pommie Well-Known Member Most Helpful Member

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    This may be conceived as slightly negative.

    This thread is so full of crap. SMD resistors to mimic an inkjet printer? An array of 16 thousand motors/solenoids!! That you're going to wind 16 thousand solenoids yourself! The suggestion that you can fire them in sequence 24 times per second. Painting wire to insulate it! This whole thread is just complete garbage.

    Whatever you (the OP) are trying to do, you will fail in your current effort.

    If you want to succeed then tell us what you are trying to achieve and not what you think the solution might be.

    Mike.
     
    Last edited: Jul 3, 2013
  20. blueroomelectronics

    blueroomelectronics Well-Known Member

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    Ain't that a fact. As for Nichrome I don't think you solder that (you crimp it). The OP has yet to tell us what he's trying to build.
     
  21. throbscottle

    throbscottle Well-Known Member

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    A heat gun can burn SRBP. Mine has a low setting - still hot enough to easily melt solder. Just be careful. A lot of SMD's are also glued on so you need a bit of force.

    Depends on how well the fluid conducts

    SMD resistors usually have a marking, capacitors usually don't. You can test them with a meter anyway. It's a numeric code, works just the same as colour code.

    I thought after my previous suggestion, small wirewound resistors would make much better heaters for this. They can stand quite a bit of heat.

    Folks, most of this might be complete pie in the sky, but it's educational to both me and (I hope) the OP, encourages lateral thinking, and you never know, the OP's unknown objective might turn out to be something we can be proud to have helped with.
     

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