Convert this circuit to be powered by DC 9v?

Discussion in 'General Electronics Chat' started by critiera119, Feb 13, 2009.

  1. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    This was from a 60 LED chaser light set, blue and white. There are 16 patterns. I would LOVE to get this to work with a 9volt for say several blue and red LEDs, 10 total maybe. Any thoughts?
    [​IMG]


    [​IMG]
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    What was the operating voltage?
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    Run time might be under 10 minutes. 9 volt batteries are very light duty.
     
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
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    Looks like around 5V...the 33uF filter cap is labeled "10V".

    Ken
     
  5. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    These are the stickers on the string:
    [​IMG]
     
  6. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    I am open to any battery and to making any modification to this circuit for it to work on batts.
     
  7. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
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    You need to power up the circuit using AC mains power, with or without the LEDs connected(does not matter) and measure the DC voltage as indicated.

    Take great care not to electrocute yourself in doing so. Don't touch any part of the circuit board with your hand except using the meter leads.

    You will need to use a DVM and not an analogue voltmeter meter because of the series 100KΩ resistor in the rectified power supply to IC connection.

    Post back with the voltage measured.

    [​IMG]
     
  8. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    Ok, I did it carefully. Glad that is over. 4.8v max on the DVM.
     
  9. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
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    Good we can use a 78L05 for the power supply then.

    However, there is a large possibility that Q2, Q3 and Q4 on the circuit are SCRs and if this is really the case, then it is NOT possible to use a battery for the controller as a SCR cannot turn off by removing the gate drive.

    I should have asked you in previous post about the part number on these but I forgot until I see a 1MΩ resistor taking signal from the rectified but unsmoothed DC supply into the controller.

    So what is all the markings on these semiconductor?

    [​IMG]
     
  10. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    Last edited: Feb 14, 2009
  11. eblc1388

    Senior Member

    Nov 28, 2008
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    As expected the PCR406J is a 400V 0.5A SCR.

    The SCR will not turn OFF once triggered. This means there is no easy way for you to use battery with the existing controller.
     
  12. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    Damn. Briefly, can you just expand just a little bit on how hard it might be to make it work on battery? I am open to changing transistors or anything else that it may require.
     
  13. eblc1388

    Senior Member

    Nov 28, 2008
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    You will need to use a 555 timer and wire it up to generate 100Hz, with the output of voltage high 95%/ low5% duty cycle. This will then be fed to both the controller and the LEDs so they will think it is AC input they are seeing.

    As the 555 timer output goes LOW for 5% of the time, the SCRs will turn off when this happens.

    This is the idea which I think could work and a 555 is easily obtainable. However there is still some uncertainty in it as no one has tried to do it before.

    Would you like to experiment with it, when there is a 10% chance of things don't work out in the end?

    Let's put this idea in the public domain for a few days and let others comment on it before actually design a circuit.

    A regular 9V battery has too little juice to last only for a few minutes. A 12V gel type battery is more appropriate for your application. What LEDs are you have in mind? Color blue?
     
  14. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    I have a couple TLC555 timers.

    I hear what you are saying about the chance of it not working out and agree. Let's see if anyone else has any input on the idea.

    Battery size is an issue, so I am not sure 12v is applicable unless there is a small one that powerful available that I don't know about. This is for a 1/18 idea and can’t be larger than a 9v, several AA/AAA or other similar size.

    16 LEDs would be a good amount to try. 8 blue, 8 red.
    These: http://www.sunteking.com/en/products_show.asp?areaid=178&id=214&flag=0
     
  15. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    That won't do. The TLC555 output can only source 10mA and cannot be used to power a total of 16 LEDs. You can only use a regular 555 like LM555 or NE555 which can source more than 100mA. Otherwise you have to add an extra PNP transistor or P-Ch MOSFET to the TLC555 to boost its output current.

    You can have up to three connections(to Q2, Q3 & Q4) for the LEDs and each connection can have multiple LEDs in series per branch and parallel branches. However, owing to the forward voltage drop of the blue LED, you can have at most two in series with a single current limiting resistor in an individual branch when 9V battery is being used. For red LEDs, you can put three in series.

    With 16 LEDs, how would you connect these LEDs to each connection?
     
  16. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    Well, I just found another 555 in my box, and it is an NE555. Thanks for explaining why I can't use the TLC though.

    [​IMG]

    Here is what I want to put the LEDs in. 4 red where the red is and 4 blue where the blue is, facing outward of course and the same on the reverse (back). If 16 can't work, then whatever equal number that will work and to have in the correct positions..
     
    Last edited: Feb 16, 2009
  17. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    Bumper................ :)
     
  18. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    Ok. Here is the circuit diagram and wiring connection.

    I only showed a single branch of LEDs per each connection you can use two or more. The limitation is the total output current of the 555 timer, which should be less than 200mA for all he LEDs. The resistor values for the LEDs are not shown but please refers to previous post about the number of different color LEDs you can place in series with the battery voltage you intended to use.

    I trust that you know how to take care of the LED connections and calculate the required resistor values yourself.

    [​IMG]
     
  19. critiera119

    Thread Starter Active Member

    Nov 21, 2008
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    Yup, I'll figure the resistors for the LEDs.

    If this works, I am getting you a prize because it is very kind of you to help me like this..... I'll be back when it is complete.
     
  20. critiera119

    Thread Starter Active Member

    Nov 21, 2008
    66
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    RadioShack does not have 78L05, can I use their 7805 for my circuit? I think not, right? Any alternatives?
     
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