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Polarization Problem

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

  1. ronv

    ronv Well-Known Member Most Helpful Member

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    Make Rext 1.5K to 2k ohms and remove any resistor in series with the input to the opto coupler.
     
  2. MEMPHIS91

    MEMPHIS91 New Member

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    which opto? I have some, and some ordered.
     
  3. ronv

    ronv Well-Known Member Most Helpful Member

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    Which one do you have?
     
  4. dave

    Dave New Member

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  5. MEMPHIS91

    MEMPHIS91 New Member

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    the one that can only handle 60mA. I dont have to computer I was using before so i dont remember to part number.
     
  6. ronv

    ronv Well-Known Member Most Helpful Member

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    K817P Opto.
    Like this.
    and make Rext 1.5k to 2K ohms.
     

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  7. MEMPHIS91

    MEMPHIS91 New Member

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    ill set it up as soon as i get home. But can you explain how exactly thats gonna make it work?
     
  8. ronv

    ronv Well-Known Member Most Helpful Member

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    With no Rext on the led driver there is no current to turn on the led in the opto. so the scr won't turn on.
    Rext of 2k will supply 10 ma for the opto to turn on. (no other resistor required)
    The resistor to the gate will limit the gate current.
    The opto in your diagram looks like it is wired wrong. Make note of the dot in my picture. That is pin 1.
     
  9. MEMPHIS91

    MEMPHIS91 New Member

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    limit gate current. but i need 330mA to turn the Gate on.
     
  10. ronv

    ronv Well-Known Member Most Helpful Member

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    BT258X = 50 ua typical 200ua max. so we should have >1 ma. with the resistor? Where did you see 330 ma?
     
    Last edited: Jun 6, 2011
  11. MEMPHIS91

    MEMPHIS91 New Member

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    with the 15ohm resistor i have from the gate to GRD
     
  12. ronv

    ronv Well-Known Member Most Helpful Member

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    Get rid of the 15 ohm resistor.
     
  13. MEMPHIS91

    MEMPHIS91 New Member

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    Read back over the last few post in the theard on pages 6 and 7. It says why I cant do that.
     
  14. SABorn

    SABorn New Member

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    As i said a long time ago in this thread the 15R resistor is a bandaid to a problem, and you still insist the 15R is needed.....find and fix the problem and loose the 15R resistor.

    As Ronv said its less than 1mA required to drive the gate, or it would not be listed as a logic level gate in the data sheet. not many chips supply a logic level higher than 20mA max, so it has to work at less than that.

    I have not been able to open any of your files to see the setup you have or how you have connected things, but if Ronv has and surgests you have the opto wired wrong than that might explain why it wont work as it should.
     
  15. ronv

    ronv Well-Known Member Most Helpful Member

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    Picture

    SA,
    Here is the picture in .png.
    Good luck.:)
     

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  16. SABorn

    SABorn New Member

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    Geez??

    Its not real clear, so i redraw it just so we can understand if we are all on the same page.
    As Memphis has trouble understanding symbols i used a block schematic approach.

    Memphis can you check this and comment if it is the same as your wiring at present so we know what you have NOW.

    The other thing is if you have wired things as you have drawn them, then the SCR might be wrongly wired on the pins, so have a look at the other snipit from the data sheet i post here and see if you have the pins correct on the SCR.

    Pete.
     

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  17. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Here is a typical E-Match spec;

    Bridgewire Resistance: 1.3 Ohm (+/- 0.1) No Fire Current:< 0.25 Amps All Fire Current: .4 Amps Safe Current for Test: < .5 ma Match Head Resistance: 1.3 Ohm (+/-0.1) Includes

    From here; http://www.pyrocreations.com/inc/sdetail/87626/83748

    Your test current needs to be much lower to be safe!

    Working with pyro, NO E-Match is guaranteed against shorting after firing! Without short circuit protection your wires may burn up!

    Fire works can kill you! I would never run a firring system off a PC! Especially one running Windows!

    Pro firing systems have fail safes built in so no one can get hurt, yours has none, dont blow your self up!

    Andy
     
  18. MEMPHIS91

    MEMPHIS91 New Member

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    Ok, so maybe the opto is wired wrong. But i do read 5V+ as though everything is working as it should. I have it wired just like SAborn had in the picture he first put up. Looks as though y'all have both 5V+ coming in one side of the opto, as I have one on one side, and one on the other. I think it just cant over come the 15ohm resistor. Do you see now why I need it? The LEDs make the gate very sensitive.

    4pyros, i'm sure we have talked about all this before. My E-match is not like all the others, when I made mine, I didn't know what a E-match was. Its just as impossible as me to poop rainbows as it is that my E-match will short out after firing.
    And yes I well know that ALL fireworks can kill.
    Worst case thing happens, they all go off at once..... That would suck, but would be a nice short show, if the mortars are set up right, there will be no safety problems. Plus i'm a Firefighter.... so I'm suppose to know what i'm doing. ;) Thanks for the concern though. If you knew all the test and stuff I had done, you would probably call me a fool. :p

    Listen guys you don't know how much this means to me. Ronv and SAborn. If you guys have paypal I would love to buy yalls lunch. Yall have been a big help, and continue to be.
     
  19. MEMPHIS91

    MEMPHIS91 New Member

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    AND the 15ohm resistor is what makes it turn off..... if that wasnt there the SCR would stay on the whole time.
     
  20. ronv

    ronv Well-Known Member Most Helpful Member

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    There must be several problems with your hook up. How about we go all the way back to Grinch and see if all is well there now that you have an Rext. Remove the opto from the circuit and add an led to a Grinch output with the cathode to the output pin. The cathode is the side with the flat on it. Put the other side to ground. No resistor should be required. See if you can turn the LED on and off with your software. If you can we can go forward to the opto.
     
  21. MEMPHIS91

    MEMPHIS91 New Member

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    It turned it on.
     

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