Settable Delay Timer with Display?

Discussion in 'The Projects Forum' started by jb_magic, Nov 28, 2007.

  1. jb_magic

    Thread Starter New Member

    Nov 28, 2007
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    I'm hoping to build a circuit that would provide the ability to set a time (hours/minutes) after which a set of LEDs will turn on. I would like a display for setting the time and have that display count down. I'm not against purchasing a prebuilt system for some/most/all of this if such a kit is available.

    A count up timer would also be fine provided I can set the time to count up to before the lights go on.

    I'm a novice at this but can follow directions and assemble parts if the schematic is good and parts list available.

    Thank you all in advance.

    -john
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    This has "micro-controller" written all over it.

    You're sure its LEDs you want to light up, and nothing objectionable? A New Years Day display perhaps? Nothing objectionable?
     
  3. jb_magic

    Thread Starter New Member

    Nov 28, 2007
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    Nope, nothing objectionable. This is for a floatation tank I've got in my garage and I'd like to be able to set a timer so that the lights go on inside the tank after a preset time period. I often go into the tank when I'm home alone and would like a nice easy reminder to come back to the world, the alarm clock just isn't working for that.
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
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  5. jb_magic

    Thread Starter New Member

    Nov 28, 2007
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    I think I'm going to mod a kitchen timer. I tore apart one I had at home last night and was able to get it to kick on an LED but the voltage wasn't enough and sadly this timer doesn't have a solid beep, instead it has some flasher circuit which I'll need to disable.

    My thoughts are as follows:

    Kitchen Timer -> Relay Switch -> LED system

    This way the LED can be powered separately and the kitchen timer would only need to activate the relay.

    thanks for any more advice, really appreciate it.
     
  6. jb_magic

    Thread Starter New Member

    Nov 28, 2007
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    Followup question...

    what would it take to have lights come on gradually, as if on a dimmer with the brightness increasing slowly until the lights are completely on? I am using LED's but I think they will simply put out less light with lower voltage.

    Thanks.

    -john
     
  7. Voltboy

    Active Member

    Jan 10, 2007
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    Use PWM, you can generate it with a 555 timer. Look at google.
     
  8. kender

    Senior Member

    Jan 17, 2007
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    I doubt that 555 can be accurate enough over the period of several hours.
     
  9. jb_magic

    Thread Starter New Member

    Nov 28, 2007
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    0
    Thanks for the tip regarding using a 555 as a PWM. From what I can tell that circuit would force a specific percent/duty cycle. I'm hoping to find something that would increase the amount of light over a period of about a minute, an auto-dimmer of sorts.

    -john
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
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  11. GS3

    Senior Member

    Sep 21, 2007
    408
    35
    A ramp at pin 5 of the 555 timer results in PWM.
    Here's an idea: Take a npn transistor TR and connect collector to pin 5, emitter to 0V, base through RC to +Vcc. as C charges slowly, TR conducts less and the voltage in pin 5 rises.
     
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