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Polarization Problem

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by MEMPHIS91, May 27, 2011.

  1. MEMPHIS91

    MEMPHIS91 New Member

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    So here the deal I'm running a DIY Board call GRINCH that uses 4 of the MBI5026GN ICs, that sink the negative. Here is the problem, I need a 1.5VDC+ to power the gate on a BT258X Thyristor.
    So I need a thingi ba bob to change the voltage from GRD to +. I would like to have it at 5VDC+.
    Any ideas? Thanks
     
  2. SABorn

    SABorn New Member

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    The thingi ba bob, went out with Elvis, and you could try a oodnawhatzit, that might fix it.

    Pete.
     
  3. MEMPHIS91

    MEMPHIS91 New Member

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    Thanks Pete. :p
    Could I use a PNP transistor? And put the base to the Grd coming from the Grinch? And the collector to the Gate of the BT258X, and 5VVDC+ to the emitter? I know that should work, but so for it hasnt....
    Any ideas?
     
  4. dave

    Dave New Member

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  5. SABorn

    SABorn New Member

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    I struggle to understand your question and guessing others do to due to the lack of answers.

    Lets see.....the MBI5026GN is a led driver correct? and the BT258X is a form of triac or scr i gather, and think its has a logic level gate.

    And what you require it to take a low level signal and convert it to a high of 1.5 to 5volt to switch the gate.

    The easy way might be to use a opto coupler as its then a led on the low side(should work with a led driver) and the transistor side connected to 5 volt feeding to the gate of the BT258X.
    This also has the advantage of isolating the 2 circuits.

    With your PnP transistor setup it wont work as you have it, and will need a pullup resistor from the base to 5volt at the very least, because the MBI5026GN is only a current sink from what i remember, so it can not pull the PnP base high at any time and requires the resistor to pull it high.

    Pete.
     
  6. MEMPHIS91

    MEMPHIS91 New Member

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    Sorry for the confussing quesstion. Its hard to ask about something that I don't know what is :p lol.
    Also there are 180 of these circuts...... so I need this to be as cheap as posible. How many circuts could 1 opto coupler control?
    Is there not a small relay I could use? I can run a parellel line of 5V+. And Just have the relay waiting on grd to turn on.

    Thanks so much for your help. I've spent a lot of money on this. :p
     
  7. MEMPHIS91

    MEMPHIS91 New Member

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    And yes the MBI5026GN is Led drivers used on a DIY board called the Grinch. Power by the parellel port on the computer which is controled by a software called Vixen. Beautiful..... it really is.
     
  8. SABorn

    SABorn New Member

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    Hell, you really are giving my crystal ball a workout here, and its only a cheap Chinese made one to start with that tells lies at times......lol.

    Are you able to post a rough schematic of what the circuit is, because it just gets more confusing as it goes.

    Ok..........180 what? Thyristors?? and if so are they all switched together at the same time.

    There is likely many ways to do this and a relay could be one method but without knowing the circuit it could cause other problems, like with the relay contacts open the gates would be floating and this could cause unwanted effects.

    A opto coupler can control several devices but it all depends on the current requirements of the devices.
    Optos are small 4 or 6 pin packages and not over expensive, but to have to add 180 of them might be costly, perhaps a hex inverter like the 4069 would do the job, as a low on the input would give a high on the output and vice versa (inverted) but this is a 6 (hex) inverter package and would likely only control 6 devices, and if each device required its own control than thats 30 chips needed for 180.

    You really need to give more information on the circuit, we dont mind if its hand drawn schematic or how your discription is, but dribs and drabs of information can only lead to poor answers in return. (hence my original reply)

    Pete.
     
  9. SABorn

    SABorn New Member

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    I just had a look at a data sheet for the MBI5026GN here
    http://www.datasheetcatalog.org/datasheets2/39/390955_1.pdf

    And from what i can see its only a current sink driver so it will supply no voltage out and only sink a voltage to ground, so no matter what device you attach to an output it will never switch high.
    You can put a pullup resistor on the outputs and when the outputs are off the resistor will pull the line high and when the outputs are on they will pull the line low, but this would mean the Thyristors would be on and turn off when the outputs were on, inverted in other words, so to correct this so when the outputs are on the Thyristors are on you would need to add an inverter as i had said above.

    Are you confused now??

    EDIT:- one final question...... you do know a Thyristor is a latching device under most conditions and will not switch off if the gate voltage is removed and will stay switched on or latched.

    Pete.
     
    Last edited: May 29, 2011
  10. MEMPHIS91

    MEMPHIS91 New Member

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    What all do you did a diagram of? You know everything now, the MBI5026GN needs to open the gate of the Thyristor. Its 180 Thyristors, each on a different channel, so they fire independently. And I have designed the board to cut off the Thyristor. I've already done all that work. So you have given me lots of ideas, but which one do you suggest? I'm working on putting the final design in pad2pad so you can see it exactly.
     
  11. MEMPHIS91

    MEMPHIS91 New Member

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    http://www.facebook.com/#!/photo.ph...79822890385.2053430.1076291087&type=1&theater

    That's a very rough diagram of the Fireboard that has 15 of the Thyristors on it. I have made 12 of these boards.

    Basic explanation.
    Computer software Vixen
    Controls Grinch via a parallel port
    Grinch ( http://doityourselfchristmas.com/forums/attachment.php?attachmentid=2&d=1181272880 ) as you know uses 4 of the MBI5026GN chips, and comes out via VGA cable
    *MISSING LINK*
    Fire Board then "Relays" 12VDC to the E fuse, and YAY!! Fireworks rain down! The Leds and other stuff on the Fireboard are test Leds and Hot Test Leds, but should have nothing to do with the Grinch and the Thyristors.

    Any more questions?
     
  12. KMoffett

    KMoffett Well-Known Member

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    Memphis91,

    Please post things here, not on links or other sites that require registration, and that will be dumped into the great bit-bucket sometime down the road, and future readers of this thread will not know of what you speak. ;)

    Ken
     
    Last edited: May 29, 2011
  13. SABorn

    SABorn New Member

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    Yes i agree, as i dont use facebook so i cannot view the image and also will not join the other forum so cannot see the second link either.

    Funny right from the start i thought .........hmmmm...fireworks?

    In actual fact you have picked a poor chip to do the data expansion with using the led driver for this application and now require to add more chips to fix the problem, the simplest would still be a opto i think but you will need one between every output and Thyristor.

    Would still like to see the circuit.

    Pete.
     
  14. MEMPHIS91

    MEMPHIS91 New Member

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    Can you get me a part number for a opto that would work? Seems like that my only route right now. Cause my show is in a month.
    Ill try to get the board stuff up here soon.

    Thanks SO much Pete for all your help. You really have been a life saver.
     
  15. ronv

    ronv Well-Known Member Most Helpful Member

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    Seems like you should be able to add a pull up to the output of the led chip and then invert the signal coming from the parallel port in your software.
     
  16. MEMPHIS91

    MEMPHIS91 New Member

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    The software is call Vixen. You are more than welcome to see if you can invert it in the software. Because I have NO idea how to. lol
    That would be awesome if I could though.
     
  17. MEMPHIS91

    MEMPHIS91 New Member

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  18. ronv

    ronv Well-Known Member Most Helpful Member

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    If you post a schematic here we can tell you if it will work.
     
  19. MEMPHIS91

    MEMPHIS91 New Member

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    the data data sheets are on the other page. a schematic is almost impossible. Led driver connected to the Thyristor via the OPTO.
     
  20. SABorn

    SABorn New Member

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    Inverting the data might not be the best idea in this case as when the circuit first fires up all thyristors will be on before the parallel port switches then off and considering this is a circuit to sequence the detonation of fireworks that might be one hell of a starting BANG!

    I think i would rather all thyristers off until they are switched on just for saftey reasons.

    Here is a few optos, there is 100's of them.


    4N32 ....... 6 pin darlington
    http://www.datasheetcatalog.org/datasheet/motorola/4N30.pdf

    4N28 ....... 6 pin
    http://www.datasheetcatalog.org/datasheet/motorola/4N26.pdf

    SFH6156 .........4 pin
    http://www.datasheetcatalog.org/datasheet/vishay/83671.pdf

    ILQ74 ..............Quad package
    http://www.datasheetcatalog.org/datasheet/vishay/83640.pdf

    Pete.
     
  21. MEMPHIS91

    MEMPHIS91 New Member

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    Out of those, which would you pick? I like the quad, or 4 channel ones the best. Probably be cheaper.

    And will each one have to power in LED to work?
     
    Last edited: May 31, 2011

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