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Will this circuit work - power latch — Parallax Forums

Will this circuit work - power latch

computer guycomputer guy Posts: 1,113
edited 2008-03-17 05:37 in General Discussion
Hi everyone,

Does anyone know of an IC that I can use that will perform the same task as a computer power circuit.

I basically want to be able to turn my device on with a momentary switch and turn it off the same way. (Like a computer does).

I am wanting to turn a hybrid into a mini arcade PC.

Thank you smile.gif

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Post Edited (computer guy) : 3/15/2008 6:07:09 AM GMT

Comments

  • LeonLeon Posts: 7,620
    edited 2008-02-18 02:41
    You could use one of the very small PICs to control the supply - put it in sleep mode and wake it up or turn it off with a key press. It'll take very little current.

    Leon

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  • computer guycomputer guy Posts: 1,113
    edited 2008-02-18 05:39
    Leon,

    Thank you for your suggestion however I am after something that is an off the shelf solder it in and go type of IC.

    Thank you smile.gif

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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2008-02-18 07:38
    I am not sure I fully understand what you want, but you might investigate the Power ON sensing feature that newer power supplies include. This has to close, in order for the PC power supply to provide power. In an arcade game, this could be switched by the coin slot. The PC would shut down either when the game is finished or timed out due to in activity.

    The coin slot pulse might have to go to a latching relay in order to remain ON for a full game cycle. The PC could shut off the latching relay at the end.

    So, that wouldn't be an IC; that would only turn on, the PC would turn off. And, there would not be any audio/video output loop trying to get people to play when the machine doesn't have a paying customer.

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  • computer guycomputer guy Posts: 1,113
    edited 2008-02-18 07:45
    Kramer,

    You know how modern PC's that when you push the power button they turn the PC on.
    This is what they do.

    1. Power supply provides 3.3v to motherboard.
    2. Motherboard detects that power button is pressed and joins 3.3v to PS_ON.
    3. Power supply detects high on PS_ON and gives full power to computer.

    I would like to replicate this with a home project.

    Thank you smile.gif

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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2008-02-19 10:52
    Well, there are specific ICs and a lot of transistor circuits for flip-flops that will latch. The only dilemma is that they must be powered at all times [noparse][[/noparse]that is what the PC does] in order to remember possition.

    You can use 3.3v for everything if that is what the PS_ON also requires.

    Another choice is the good old 555 timer in a CMOS version like the 7555.

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  • computer guycomputer guy Posts: 1,113
    edited 2008-02-19 11:47
    Thank you.
    I will look into these further in the morning. smile.gif

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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2008-02-19 12:12
    The Art of Electronics will provide you with with a good way to chose the right IC. There have been many generations and some are more hardy than others. Some generations have strange quirks. Also, some are too fast for manual button pressing.

    Usually I start out with 74HC??? unless something is suggested.

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  • computer guycomputer guy Posts: 1,113
    edited 2008-03-15 04:34
    Will the attached circuit work?

    The 6v will come directly from the power supply and the output will go to the 5v and 3.3v regulators.

    Thank you smile.gif

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  • computer guycomputer guy Posts: 1,113
    edited 2008-03-17 05:12
    Anyone? smile.gif

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  • phil kennyphil kenny Posts: 233
    edited 2008-03-17 05:33
    Personally, I'd place a 4016 hex Schmitt trigger after R1/C1 to make the
    rise time for the clock faster. As it stands, you have a very slowly rising
    signal into the clock pin. Logic devices don't usually like such slow
    rise times.

    What does pin 13 of the 4013D drive?

    Post Edited (phil kenny) : 3/17/2008 5:39:41 AM GMT
  • computer guycomputer guy Posts: 1,113
    edited 2008-03-17 05:37
    A stated above the 4013 will get its power from an unregulated 6v power source.

    Thank you smile.gif

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