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Integrating high voltage to bs2px24 — Parallax Forums

Integrating high voltage to bs2px24

SILVER777SILVER777 Posts: 13
edited 2008-07-12 21:45 in BASIC Stamp
I'm currently running a bs2px24 chip that i have programmed to cycle between 4 different points that i would like to send some very high voltages to. (by very high i mean anywhere from 500v to 3kv)

i was hoping that someone here would be able to help me grab some ideas as to how to introduce that high of voltage without blowing up the stamp from either direct contact or feedback.

Thanks and i really appreciate the help.

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-07-08 14:38
    It sounds like you need to use a relay to switch the high voltage and any relay would need to be rated for the voltage and current you expect to switch. Nuts and Volts Column #6 (www.parallax.com/Resources/NutsVoltsColumns/tabid/272/Default.aspx) talks about using transistors for switching things like relays. The ULN2803 that the column discusses would be handy for controlling multiple relays since it's an 8 channel device and you can parallel channels to increase the possible current. It also has the protective diodes (mentioned in the article) built-in.
  • SILVER777SILVER777 Posts: 13
    edited 2008-07-09 12:23
    well, maybe I'm blind (most likely the case) but I couldn't find the reference in column 6. But what I've decided to do is use an optocoupler (mct6) in series with the chip followed by a relay (LH1540AT). this should stop any backfeed into the chip and still fully utilize the switching that I want.
  • JomsJoms Posts: 279
    edited 2008-07-10 21:28
    Perhaps it would not be a bad idea to also add an optic-isolator chip in there if you are dealing with that high of a voltage difference.· A optic-isolator chip has a tiny LED inside with a small photocell so there is really no electrical connection between the chip and what you are trying to switch.· Some chips have a transistor built in so you can have the stamp connect to the chip, then the chip directly can control the relay of your choice....
  • SILVER777SILVER777 Posts: 13
    edited 2008-07-11 12:45
    yeah, that's kinda the same direction that we are going. The optocouplers that I listed have that same configuration, it's kinda all in how you set it up. I tested them yesterday and it looks like it will do everything that I hope for. The final product should be done in a matter of weeks now. [noparse]:)[/noparse] it's amazing what you forget when you don't use it on a day to day basis. [noparse]:)[/noparse]
  • DaveGDaveG Posts: 84
    edited 2008-07-11 15:12
    Howdy,

    Perhaps I don't understand your whole system, but it sounds like you are planning to use the LH1540AT solid state relay to directly switch the high voltage.

    I looked at the specs for that device and it is only rated to handle a maximum load voltage of +-350 volts. The 5300 volts mentioned in the spec is the isolation voltage, not the switching voltage. I would suggest looking for a relay that is rated for at least 5kv, at whatever your maximum current might be.

    Dave
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2008-07-12 21:45
    You could do this down and dirty (and sparky[noparse]:)[/noparse] by making your own high voltage relays for each distribution point...

    make a contactor set out of some roofing copper wrapped on a nail head for one side of the contacts. For the other contact, use a copper-wrapped nail driven into a wooden dowel that is in turn expoxed to a solenoid's driver shaft. Drill a small hole in the dowel for the shaft. Mount the dowel assembly in a teflon or plastic tube, or rest it on a groved version of same material. Mount the first contact side similarly, with a set screw to adjust the gap.

    Now all you need is a plain old solenoid. Just make sure you don't get arcing or plasma overflow from the contacts to the low voltage side. Opto isolators won't help unless you stop the arcing first! You can block this with some grounded aluminum window screen a half inch or so around the solenoid. And put the solenoid leads inside a copper or steel braid.

    This works surprisingly well. The contacts will burn out faster or slower depending of course on duty cycle and how quick the solenoid plunger closes the gap. Once the contacts are toast, merely peel them off with a pair of needle nose and put new ones back on.

    I have used this set up for Tesla coils and for wild-science displays using a TV's fly-back coil (ca 30kV).

    If you're using hi V. ~AC~ watch your P's and Q's! The higher the freq., the more wild and wondering the arcing will get. Also be wary of generating X-rays --- this can happen even if the contacts are not in a vacuum! You can enclose the contactors in stout container.

    cheers
    - Howard
    My Legal disclaimer: these are lethal voltages - there, I told you so ... and kids, don't try this at home (Unless you LIKE the Mad Scientist's Hairdo)

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    Buzz Whirr Click Repeat
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