Why does a copper coil stop circuit from working?

Discussion in 'The Projects Forum' started by Tony357, Mar 24, 2015.

  1. Tony357

    Thread Starter Member

    Mar 24, 2015
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    Hi everyone,

    I have built an LED chaser circuit with 7 LEDs as outputs.

    I want to modify the circuit by making it a bit more powerful so the LEDs shine bright and then exchanging each LED for a coil of copper and this is where i hit the problem.

    So far i have added a darlington pair to each output to bust the current and then replaced an LED in the centre of the 7 with a copper coil as i power up the circuit the lights flow as normal until they reach the copper coil, then the circuit stops?

    Can anybody tell me why the cycle will not complete?
    ( I have enclosed a basic diagram that i started with as i can not upload any pictures at present sorry) also i have spotted the mistake on the 4017 as the pin next to 8 is meant to be 13 not 3.
    7-Led chaser cct.jpg
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    What is the copper coil supposed to do???

    It would appear as a dead short if it replaces the LED, which shorts the power supply, pulls the supply voltage down, and resets the counter???
     
  3. Papabravo

    Expert

    Feb 24, 2006
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    Latchup would be my first guess. What makes you think a copper coil is in any way equivalent to an LED? They don't produce light. They have a very low impedance. What were you thinking?
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    Doesn't R2 @ 100 Ω provide a wee bit 'o protection?
     
  5. Tony357

    Thread Starter Member

    Mar 24, 2015
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    I wanted the coils to produce a magnetic field, one after another as i have an idea of a project to build if i can do so.
    Is there a way i can accomplish this please?

    (I am not an electrician or anywhere close i just have ideas and would like to see if some work).

    Thank you for your reply.
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    No. A copper coil is going to short the outputs of the 4017. When one output is trying to go HIGH, all the current will flow into all the other outputs which are sinking current. You are creating a dead short across the power supply through the outputs of the poor 4017.
     
  7. Papabravo

    Expert

    Feb 24, 2006
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    OK, I see that now.
     
  8. Tony357

    Thread Starter Member

    Mar 24, 2015
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    Thank you for your reply.

    Would you know of a a circuit that would fire 7 copper coil outputs one after another please?
     
  9. MrChips

    Moderator

    Oct 2, 2009
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    What is the resistance of the coil?
    What is the voltage and current each coil needs?
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    As MrChips pointed out you have to consider each output of the 4017 as a separate and independent circuit. It sorta works with diodes because they only allow current to flow in one direction. The proper circuit would be be one resistor and one LED per 4017 output. If you want a coil to replace the LED you need to increase the resistor to limit the current. Keep in mind that a 4000 series CMOS device cannot supply very much current. Look in the datasheet for parameters Ioh and Iol. They refer to the current with the output high and the current with the output low. Will a couple of milliamps create enough of a magnetic field for your purposes.
     
  11. Tony357

    Thread Starter Member

    Mar 24, 2015
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    A circuit that produces a couple of milliamps should work i might have to play around with the size of the coils but i will try anything as this is not working
     
  12. MrChips

    Moderator

    Oct 2, 2009
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    What are you trying to build?
     
  13. ScottWang

    Moderator

    Aug 23, 2012
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    Because the the resistance of copper coil is very low as short wire, any other output only connected a led to ground and it as a 9V cross on a 2V or 3V LED.

    Do you have the datasheet of copper coil or any infos about the copper coil?
    What's the purpose of copper coil?
     
  14. Tony357

    Thread Starter Member

    Mar 24, 2015
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    to
    I need the coils to act like an electromagnet if that helps, but i need them to fire and turn off one after another is there a circuit that would allow me to have 7 output coils?
     
  15. ScottWang

    Moderator

    Aug 23, 2012
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    Still no answer.
    Do you have the datasheet of copper coil or any infos about the copper coil?
    And the questions as MrChips asked in #9?
    If you want to get a properly answer then you need to offer the infos what the members asked, otherwise you won't get much help.
     
  16. #12

    Expert

    Nov 30, 2010
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    You can add a bunch of driver transistors.
     
  17. ScottWang

    Moderator

    Aug 23, 2012
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    There is no spec of the copper coil, otherwise I will suggest the mosfet, becasue that he want to using it as a electromagnet, so I guess that it will be need a great current.
     
    #12 likes this.
  18. #12

    Expert

    Nov 30, 2010
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    Well, I got the idea presented. After you have the logic in place, "How much current" is only a matter of which transistor(s) to use.
     
  19. ScottWang

    Moderator

    Aug 23, 2012
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    Since the frequency of clock is only about 6.8hz, and each coil only working about 0.147 second, so maybe no need to use the mosfet ... :)
     
  20. #12

    Expert

    Nov 30, 2010
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    You never know. This guy might try some hand wound coils under one millihenry. That's what R2 is about in my drawing. Otherwise, he could short out the power supply fairly quickly.
     
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