Flip-Flop Circuit HELP

Discussion in 'The Projects Forum' started by Warren Pnigel, Feb 16, 2015.

  1. Warren Pnigel

    Thread Starter New Member

    Feb 16, 2015
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    Hi everyone, I am writing this in regards to help I need for a project I am working on. I aim to make a circuit like the first one on this page: http://www.talkingelectronics.com/projects/5-Projects/Projects16.html

    However, I don't intend to be driving LEDs, just other devices that run off 9 volts. Basically I need for this circuit to output 9 volts from each output, and to alternate between outputs as fast as possible (so fast that for instance if you had 2 LEDs you would see them both on at the same time, but in fact they would be alternating). I hope what I'm saying makes sense, and I do realize that with these parts my goal may not be realistic.

    If this is the case, please provide a link to a suitable circuit, and for reference I am not circuit-literate, so please do not use technical jargon! Much appreciated for any help and thanks!!
     
  2. Ramussons

    Active Member

    May 3, 2013
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    What is the device you wish to run off 9 volts? We need to know what is the current requirement of this device to do any thought process.
    When you say as fast as possible, it is difficult to presume "fast". Anything greater than 60 cycles is good enough to fool the eye as far as the LED's are concerned.
    Please tell us what you have in mind. That will give a lot more useful responses.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Last edited: Feb 16, 2015
  4. Reloadron

    Active Member

    Jan 15, 2015
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    OK so you don't plan on any LEDs. As fast as possible is not a good answer. There are plenty of ways to go about this but you need to define a speed or better put timing. The average person would be hard pressed to see the LEDs change at a 100 Hz rate (each on for 5 milli sec or .005 sec) you can have faster or slower so you really need to define the speed. That said what do you plan to drive with the outputs? The little flip flop we are looking at only drives a few low current LEDs so what do you plan to drive?

    Ron
     
  5. Warren Pnigel

    Thread Starter New Member

    Feb 16, 2015
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    I was planning on driving two electromagnets I have made. They work fine off 9 volts, and I wanted current to switch between them quickly so I could make a motor using them. I need the motor to be able to spin as fast as possible, hence needing the current to switch as fast as possible. Thanks heaps for the assistance guys!!
     
  6. Ramussons

    Active Member

    May 3, 2013
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    The circuit by itself may not drive the electro magnets.

    What is the current that will flow thru' the electromagnets? If it's a couple of Milliamps, you may be able to drive it.

    The frequency of the Flip Flop will change depending on the current drawn. The circuit will stop oscillating beyond a certain limit, your "motor" will not work beyond a certain speed.

    You will need to drive the 2 Electro magnets with a phase shift, not in opposition like this setup will.

    If you can give more information on the Electromagnet - size, inductance, core material, . . . and your plans to make a Motor, there will be many more members discussing other ideas on the topic.
     
  7. Warren Pnigel

    Thread Starter New Member

    Feb 16, 2015
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    I'll build the magnet based on what works best with the circuits, so Its sort of a get the circuit working first scenario.
     
  8. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I have a lot of questions. Sorry, but it's how I think.
    • Simple motors work by reversing the polarity of the magnets; not by turning them on and off. Do you agree/disagree with this?
    • Is your objective to use a flip flop to drive a motor or to make a motor and looking for a way to drive it?
    • If the latter, have you considered alternatives to the flip flop?
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Do you understand the significance of the magnet coil inductance?
     
  10. Marcus2012

    Member

    Feb 22, 2015
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    You can use a 555 astable timer to output pulses at a set frequency and then use a JK Flip-Flops to give a clear and complementary output based on your input. This output can then be used to drive base contacts on NPN transistors that will close the electromagnet circuit. Just remember the output from the JK FF will be 1/2 of the frequency of the 555 Pulse. This would switch between electromagnets at any set frequency up to the 555 limit (1MHz iirc) but would NOT give any OFF period at all, for that you would need further logic and a 2nd JK FF. As other members have mentioned though there are other resistive forces exerted by alternative current in coils and this will affect your load. Another thing I wasn't sure about was if you required opposite polarity at any one time from each opposing electromagnet because if this is the case you'll need a truer form of A.C. (i.e. change in direction of current flow not just a stop in flow).

    Hope that helps :)
     
    Last edited: Feb 27, 2015
  11. Marcus2012

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    Feb 22, 2015
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    Oh I should have said don't bother making a JK- flip flop you can get a dual one on ebay for $1-2. And basically the setup you want for the JK FF is called "toggle" so basically it will "flip" on the negative edge of a waveform. You'll need to check the datasheet for that setup.
     
  12. Warren Pnigel

    Thread Starter New Member

    Feb 16, 2015
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    Yes, simple motors work by reversing the polarity of the magnets. However, they do this with brushes, which wear out over time and when building one yourself, can cause sparking. I'm trying to build a brush-less motor or stepper motor. The only thing I have heard of which could potentially drive this is the flip flop circuit which is why I suggested it. If you have a better alternative, I'd really love to hear from you :)
     
  13. Warren Pnigel

    Thread Starter New Member

    Feb 16, 2015
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    And Marcus2012 I didnt intend on reversing the polarity. Did you have a link for the circuit I need on ebay?
     
  14. Marcus2012

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    Feb 22, 2015
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  15. Marcus2012

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    Feb 22, 2015
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    I got bored and it wasn't much of a change from the setup in my modified sine wave generator so I have made a diagram based on what I would have done (not sure if you really need a voltage regulator on a circuit like this but depends on battery), The 555 output frequency is set via R1, R2 and C1 values, any 555 astable guide can explain this. When I was making my generator I needed to understand flip flops and the best way is to look at the wave forms produced, a guide on instructables showed me this.

    In the diagram below you see the 555 output pulses and below that is the two outputs from the JK FF (clear and complementary). You see how the JK FF only "flips" and "flops" on the transition from high to low on the 555 output pulse (negative edge). So as a result from the JK FF you have one output that is on when the other is off. If you use these outputs to power the base of the transistors you can alternate the flow between each coil at a frequency that suits you. An added (needed) benefit of the JK FF is that the duty cycle of the output will automatically be set to 50% regardless of the 555 duty cycle due to the nature of its function, the cost of this is a halving in frequency so set the 555 accordingly (i.e. twice what you need).
     
    Last edited: Feb 27, 2015
    Warren Pnigel likes this.
  16. Warren Pnigel

    Thread Starter New Member

    Feb 16, 2015
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    Thanks! I'll have a look into this :)
     
  17. Warren Pnigel

    Thread Starter New Member

    Feb 16, 2015
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  18. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    No.
    Reduce the cap values or the base resistor (R3,R4) values.
     
  19. Warren Pnigel

    Thread Starter New Member

    Feb 16, 2015
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    The cap values will speed it up if I reduce them. What is the minimum I can reduce these to?
     
  20. Marcus2012

    Member

    Feb 22, 2015
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    That circuit will provide you with neither the power for your electromagnets nor the synchronisation you require for your function and I wouldn't be surprised if the longer this runs the more out of sync it will become especially at a high frequency. Can you go into more detail on your application for this please and what kind of torque you are expecting? You mentioned stepper motors and brushless motors earlier but these run of an AC source or from an integrated inverter and use waveform manipulation depending on application (half-stepping etc). I think you may need more coils too.
     
    Last edited: Mar 2, 2015
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