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waterfall printer

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by kagan09, Dec 17, 2010.

  1. SABorn

    SABorn New Member

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    The tinkle, tinkle might make you want to take a twinkle yourself rather often, hope the toilet is handy.

    Sounds like you are suffering (or rather your circuit) from some lag in the fets turning off fast, and perhaps should have had a driver on each fet.
    I dont recall if the IRF540 is a frequency fet as some dont like high speed switching and am guessing this is the case here.

    I am no expert on fets and have run into many problems with them myself, one thing i have learnt is the right fet for the job makes a world of difference and the manner they are driven with is important too.

    At high speed do the fets run hot at all?

    Pete.
     
  2. Khalid1349

    Khalid1349 Member

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    Hi Pete,
    Your first sentence is totally Alien to me;)...Did not understand...
    The FET is very Cool through out the process... The lag was due to the Diode not by the FET,... If you are involve in CNC machining most of the controller uses Power MOSFETS, they do switching at very high speed...
     
  3. Khalid1349

    Khalid1349 Member

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    Here is the tubing and wiring of solenoids..
     

    Attached Files:

  4. dave

    Dave New Member

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  5. Sceadwian

    Sceadwian Banned

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    The diode allows the inductor current to hold the solenoid open for a short period of time as the magnetic field collapses which is the delay you're experiencing. You need a push/pull FET arrangement to avoid this. Without the protection diode that inductor current IS definitely going somewhere, and that's an avalanche over voltage event for the FET. This doesn't mean it's necessarily bad, but you better have chosen (by luck in this case) a solid FET that is avalanche rated for the reverse pulse's it's getting or you'll fry every one of those suckers the first time you try to use it for any length of time.

    http://www.electro-tech-online.com/custompdfs/2011/05/AN-9034.pdf
    Might provide some greater insight.
     
  6. kagan09

    kagan09 New Member

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    Hey khalid i went scrap yard for solenoids they didnt know about it. what part of the car are the solenoids so next time i go ill be more specific
     
  7. cr0sh

    cr0sh Member

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    Most likely he went to a general scrap yard, not an auto-specific one (just guessing, though) - if that's the case, then most of those valves would likely come from machinery which controlled water or other liquid sources, such as drink machines, refrigerators (ie, water dispenser), dish washers, clothes washers, etc. I'm sure there might be a few such valves on some automobiles, but I've never run across any, yet...
     
  8. KMoffett

    KMoffett Well-Known Member

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    Fuel injector solenoid valves?

    Ken
     
  9. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    thay most likely came from an industrial scrap yard.
    Andy
     
  10. cr0sh

    cr0sh Member

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    Nah - fuel injectors look nothing like those valves...
     
  11. KMoffett

    KMoffett Well-Known Member

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    No, I meant would fuel injector valves work?

    Ken
     
  12. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Maybe but thay have a pretty high operating pressure. Witch means you would have to switch them supper fast to try and get one drop at a time. Maybe thay can be modifyed?
    Andy
     
  13. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    cr0sh is right. Forget the injectors. They are intended for a much smaller volume at a much higher pressure.

    I would like to see someone try using constants streams of water and diverting the unwanted ones instead of stopping and starting the flow.
     
    Last edited: May 10, 2011
  14. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    I think I just said that.
    Andy
     
  15. cr0sh

    cr0sh Member

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    First, my apologies for misinterpreting your question, KMoffett; besides what 4pyros noted, though, I think the other problem you would probably face with injectors is that they don't output a stream, but a spray (likely a fairly fine spray) - given that they are meant to disperse fuel into the air intake of a cylinder (so you want it to transition to vapor as quickly as possible). Maybe it might be possible to disassemble such an injector and modify the nozzle? Another possibility might be injectors from a diesel engine (they might be easier to disassemble and modify). It's an interesting idea, if you can get it to release a stream of water rather than a spray (maybe it sprays only under high pressure - maybe they might work under lower pressures, with a stream instead?). The nice thing about such a valve is it high operating speed (which would translate into more drops per second, which would mean greater vertical resolution); the bad thing (if you went new parts, of course - though even used could be an issue) is cost (at one time I was going to replace the injectors on an old Neon, but the cost per was something like $60.00 with core at Checker).
     
  16. KMoffett

    KMoffett Well-Known Member

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    I have little knowledge in the automotive engine world. :( I was just thinking of the speeds they have to operate at seemed like they might work for this application.

    Ken
     
  17. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    I am not sure that "drops per second" is the right was to think of solenoid speed. Seems to me that we are looking at segments rather then drops.

    clock.JPG


    Getting water to exit the valve at near its terminal velocity should be considered. Too slow and the image will stretch at the bottom, too fast and the image will compress at the bottom.

    There is also the problem with surface tension altering the water's shape as it falls.
     
    Last edited: May 10, 2011
  18. Sceadwian

    Sceadwian Banned

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    The users current solenoids will probably work, they just need push pull drivers.. The perceived slowness in the solenoid reaction is because it's a single drive transistor per solenoid so when it switches off and the freewheel diode conducts the solenoid is held open by the collapsing magnetic field from the inductance in the solenoid coil... A push/pull driver will allow that current to be dumped into ground, or better yet a negative rail slamming the solenoid shut, I'd actually be worried about the physical construction of the solenoids at that point as the stresses will be quiet high.
     
  19. kagan09

    kagan09 New Member

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    with an injector don't you get a spray not a clean droplet. how we going the get a clear image if its a spray

    kagan

    editting : sorry didnt see this page when writing this
     
    Last edited: May 11, 2011
  20. RMMM

    RMMM New Member

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    Sceadwian is ontime with the push-pull driver. A touch of neg voltage to SNAP the solenoid off would speed up the shut off time. Letting the coil charge drift to ground will give you a much slower shut-off/.
     
  21. cr0sh

    cr0sh Member

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    Looking at the still image you posted, I am fairly in agreement with you, 3v0; I would still argue, though, that the faster the solenoid, the more vertical resolution you'll get (shorter segments). My original thoughts were drops were being used, with more drops spaced close together to make a "line" (or a "segment", as you put it); but perhaps these are streams, and not a bunch of drops...hmm.
     

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