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Hall effect switching info needed

Discussion in 'General Electronics Discussion' started by nomanoba, Jul 26, 2017.

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  1. nomanoba

    nomanoba

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    Jul 25, 2017
    Hello,
    I am building an electro-mechanical aero engine and I need to switch on power to a coil every time a piston is so called fired. There are 18 pistons and the prototype will hopefully get up to 1,000 rpm, meaning I have to switch on the coil 18,000 times a minute.

    18 magnets to do this operation is no problem. Question is, can a hall effect circuit cope with the speed that the magnets would pass it. I don't have much electronic knowledge and have designed the engine using my knowledge of internal combustion engines, as the two are very similar in operation.

    I was going to use a micro switch with 18 humps on the main rotor, but at high speeds it bounces too much.

    Will be eternally grateful for a good answer,

    Many thanks
     
  2. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Yes, a hall effect switch can easily handle that level of switching speed. 15kHz is no problem on some devices I have. (900,000 pulses per minute)
     
  3. Minder

    Minder

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    Apr 24, 2015
    If you need a miniature device, I have used the Honeywell SS400 series.
    M.
     
  4. nomanoba

    nomanoba

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    Jul 25, 2017
    Thank you, I will look it up.
     
  5. nomanoba

    nomanoba

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    Jul 25, 2017
    Wow, that info has put a big smile on my face.
     
  6. nomanoba

    nomanoba

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    Jul 25, 2017
    Ok, I now have sensor, now how do I make that switch power to a coil that draws around half an amp at 12 volts.

    I'm a bit of an electronics dummy so simple explanation needed.

    Thank you in advance.
     
  7. Minder

    Minder

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    Apr 24, 2015
    Depending on the sensor chosen, a Mosfet device should do it, but if switching at a high rate the coil response may again be a limiting factor, due to its switching response time.
    M.
     
  8. nomanoba

    nomanoba

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    Jul 25, 2017
    I never thought about the coil response time...oh well back to the drawing board lol.
     
  9. duke37

    duke37

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    Jan 9, 2011
    The problem will be the inductance of the coil. You will need a short pulse which will need a high voltage to turn the coil on and a high voltage will be generated when turning the coil off. You will need to experiment with a short puse at say 100V and a fet which can stand 500V.

    The coil will need to have excellent insulation to prevent interturn shorts.
     
  10. nomanoba

    nomanoba

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    Jul 25, 2017
    Duke, I like the way you explain (I'm autistic and not a good reader) so may want to lean on you a bit with this one. I've redesigned and reduced the 18 small pistons to 3 of the same capacity in order to give the coil a better chance of relief. The only reason I was going to use 12 volts is because it was available and safe, but if 100 volts cuts me a bit of slack, then so be it.

    Is the shorting problem common, and does the laquer not offer good enough insulation?

    Thank you everyone, much appreciated.
     
  11. Bluejets

    Bluejets

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    999
    Oct 5, 2014
    One I've built and used for many years.
    Hall effect has changed over the years as some are superseded but current one is Allegro A1120.
     

    Attached Files:

  12. duke37

    duke37

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    Jan 9, 2011
    I have some electromechanical counters rated at 4V, they can stand 4V continuously. In order to get higher speed, I intend to run them on 12V pulses so they only pass current for some of the time and should not get hot, I will see if the maximum count speed will be much higher.

    The insulation of the wire seems to be sufficient for mains transformers. I believe that some wire is triple coated. The insulation has to resist the potential between adjacent turns, this may be quite low. Is can be quite high between layers. An ignition coil has a layer of insulation between winding layers to help this. You will need to limit the inductive voltage to what the fet can stand.
     
  13. nomanoba

    nomanoba

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    Jul 25, 2017
    Thank you so much BJ, I'm guessing the mosfet does away with the need for a relay and that makes things so much easier and straight forward :)
     
  14. nomanoba

    nomanoba

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    Jul 25, 2017
    The winding of the coil is a task and a half as it is not standard in any way, so a labour of love...a few more hours insulating properly is well worth the effort I think.
     
  15. Minder

    Minder

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    Apr 24, 2015
    Could you not construct what you need from a fuel injector? Possibly adapt it.
    There are plenty of sources to experiment with from auto wreckers.
    M.
     
  16. nomanoba

    nomanoba

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    Jul 25, 2017
    Would this be better suited than bluejets circuit?
     
  17. Minder

    Minder

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    Apr 24, 2015
    This was not so much about the circuit as the coil component you mention having to build.
    In this case using a Injector (coil).
    A circuit similar could be used using a power Mosfet.
    M.
     
  18. nomanoba

    nomanoba

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    Jul 25, 2017
    The coil I need to use is not conventionally wound, but using the same wire, length and thickness could help, as I know nothing about coils or how to maximize their efficiency. Unfortunately I am in a catch 22 position, as in, I cannot reveal too much as I do not have a patent, but to obtain that patent I need a working prototype. If there were a confidentiality agreement, dare say I'd kidnap someone from this forum to do all the calculations for me lol.
     
    Last edited: Jul 26, 2017
  19. Minder

    Minder

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    657
    Apr 24, 2015
    If you have nothing at the moment how did you arrive at 1/2 amp current draw?
    It seems you have taken on quite the task of designing a specialty coil with no prior experience.
    If the automotive injector falls within the realm, at least dismantling one would give you a little insight to the demands of high speed metering solenoids.
    M.
     
  20. nomanoba

    nomanoba

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    Jul 25, 2017
    Exactly, an education I need. ps. I'm a good guesser.
     
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