Automatic On Off Switch

Discussion in 'General Electronics Chat' started by Knowlittle, Mar 20, 2016.

  1. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    Hallo out there all my learned out there ! I am in need. ... i have constructed a circuit with a coil a few caps and a manual switch. When pressing the switch the voltage would climb. I need 2 things ...1) need to "override" the manual switch with an automated one so the circuit switches automatically 2) stabilize the output voltage ! I hope you can assist !!
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Without a schematic (or at least a block diagram) of your circuit and a better description of it's intended function it will be difficult to assist.
     
  3. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    Volt circ.jpg

    The circuit
     
    Last edited by a moderator: Mar 20, 2016
  4. Alec_t

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    Schematic? Intended function? Power supply?
     
  5. dl324

    Distinguished Member

    Mar 30, 2015
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    We can't follow the circuit. A schematic would be best.
     
  6. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    This is connected to a coil (copper and black) other two are outputs. Dont really have a sceamatic. Will tey and draw one.

    Forgot to draw in the diode !
     
    Last edited by a moderator: Mar 20, 2016
  7. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    I understand. When the coil and the battery is connected and the button is pushed repeatedly it "pumps up" the voltage (quite a bit), what i want to do is replace the manual switch with an automated one (dowing the pressing on my behalf), then before the output i want to "bank" the captured voltage. Almost like a stun gun. No real purpose for the circuit yet, but sure when it works i will find a purpose for it.
     
  8. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    Thank you very much, appreciated! ! Can you mabey suggest a sceamatic i can try to maintain this voltage ?, even small voltage is good around 12v with sufficient current ?
     
  9. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    Thanks alot, I do understand what you are saying, and really appreciate your assistance ! im trying ! (Hihi) ! Thanks again.
     
  10. dl324

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    Mar 30, 2015
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    There's not really much point in driving the switch with a fixed frequency, fixed pulse width oscillator. You need a feedback loop to control the output voltage.

    Don't try it without voltage regulation; you'll just damage your caps and/or transistor.
     
  11. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    Guys please bear with me, ive been doing this for only a month now ! I really am not stubborn or arrogant !!, im just having a hard time understanding some of the things (i always try to apply logic) ! Ok what i am trying to build is a small very simple variable dc powered transformer (power supply), say you would input 3v, but run components to rhe "value" of 5volt.....would this be at all possible ! ..... sorry again if i sounded at all arrogant !! My apologies!
     
  12. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    So, what you're after is a DC/DC converter. There is plenty of literature about those on the net, and a quick google should find you heaps of example circuits.
     
  13. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Yes, it is.
    Good.

    Post #3 and post #6 clearly indicate a diode. As both dl and Alec managed to figure out, but you cannot, is that he is trying to reinvent a regulated boost converter. Without knowing the details, he has recreated one of Faraday's experiments and is asking about a) how to drive the switch continuously so that the boosted output voltage is continuous; and b) how to stabilize the output voltage over a range of load currents. While neither of these is an entry-level or beginner's-level question, both will "work". If you will recall, the Kettering automobile ignition system went on sale in 1910. Also, all CRT displays starting with TV sets in the 1930's have a similar circuit, as do every laptop, cell phone, and tablet battery charger ever made. I'm not sure if the total number of flyback power supplies produced is over 1 trillion, but if not, it's close. So I think this circuit has promise.

    ak
     
    Last edited: Mar 22, 2016
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  14. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    Thank you AnalogKid....You understand exactly 100% what i want to accomplish !

    " regulated boost converter. Without knowing the details,........ a) how to drive the switch continuously so that the boosted output voltage is continuous; and b) how to stabilize the output voltage over a range of load currents.............So I think this circuit can work."

    Well as i said, i am very new to this (still battling to read basic schematics), but my "Logic" tells me that the idea i have, which AnalogKid so adequately explained, could work !

    So ... who can help, or are you going to make me suffer (hihi)

    Cheers


    "
     
  15. Alec_t

    AAC Fanatic!

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    This explains boost converter operation.
    And here are some converter circuits.
     
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  16. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    Thank for the link, this however is exactly what i built, my question now is how do i maintain the boosted output voltage and keep it continuous
     
  17. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    looking at this schematic, it seemt to be what i am looking for in regards to the switching, but will the cap serve as a continous "regulated" output boost converter.gif ?
     
  18. #12

    Expert

    Nov 30, 2010
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    No. There is a bunch of smart stuff between the capacitor and the base of the transistor.
    I don't know whether to say it's bad or good, but you're a little late to the party on this one.
    My point is, you can buy a chip to do all the smart stuff for a couple of dollars.
     
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  19. InspectorGadget

    Active Member

    Nov 5, 2010
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    Also, that schematic in post #17 is a "buck" converter, a step-down converter. I thought you needed a boost converter.
     
  20. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    The diode in post #17 should be reversed if you want the top of the cap to be the +ve terminal.
     
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