Limitation of usage

Discussion in 'The Projects Forum' started by Lightfire, Feb 4, 2011.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    Hello,

    I was wondered last night about that project.

    Well, my project was about "limit".

    For example, I will limit my light usage. After one hour of using the light, it will OFF automatically.

    And this one, I want my devices will ONLY ON if the set time has begun.

    For example, I set my light at 7:00 AM then it will on at exactly 7:00 AUTOMATICALLY.

    I know this is a bit silly or so but please help me to have it true. :)

    Can somebody help me???
     
  2. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    This is what time switches are for. The electromechanical ones using synchronous motors are OK if you have a reliable mains supply with a stable frequency.

    If your mains supply is not reliable, a quartz-based timer could be better. That might cost you a bit more, and one down-side is that it might not be so tolerant to spikes on the mains - these timers often use solid-state switching.
     
  3. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Yea, but he wants a timer that counts down from the on time.

    It can be done but not easily, I'd use a photocell (or equiv) + circuitry to control a triac. When the light is on it triggers a timer that starts a countdown circuit.

    Come to think of it a few solar cells would run a CMOS 555, someone take it from here please?
     
    Last edited: Feb 4, 2011
  4. wayneh

    Expert

    Sep 9, 2010
    12,094
    3,033
    The timers I use for my Christmas lights were under $4 and have a programmable on and off sequence, a battery backup, and a an LED time readout. I think that will be tough to beat with any DIY project.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    Actually that is very easy. I have some experiments written for Volume 6 showing a 555 monostable that will come close. A 555 is a integrated circuit, a very common one.

    If you are wanting to do this with your house wiring I strongly recommend against. If it is with a flashlight or LED circuit then let me know what you want.
     
  6. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    No. I don't want to die yet. :)

    Am, I will just use it with a 12 v halogen lamp. :) and will be operated by a 12 volts battery at the same time. :D :D

    Anyway, what I want is to open the halogen lamp automatically at the set time (for example 7:00 in the morning) and then it will close after one hour has been counted...

    Anyway, what is the different between dry cells and voltaic cells? I've noticed that dry cells are weaker than voltaic cells. How true is this???
     
  7. wayneh

    Expert

    Sep 9, 2010
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    Bill will want to know the wattage of your light
    You really should start a new thread when an off-topic question comes up. And you should first read what Google can show you very quickly, for example:
    http://en.wikipedia.org/wiki/Battery_(electricity)
    http://www.ehow.com/about_5510631_wet-vs-dry-cell-battery.html
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    Actually it is really easy. Most MOSFETs turn on with really low ohmage and decent current specs. I don't know what kind of electronics stores or parts are available where Lightfire is though, so I'll assume a generic device.

    Using a similar schematic to the 555 Monostable, here is how you would adapt it to a MOSFET and light.

    [​IMG]
     
    Last edited: Feb 5, 2011
  9. wayneh

    Expert

    Sep 9, 2010
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    You're right; that'll work for any reasonable wattage the bulb might have. But it won't turn on at 7AM.
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
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    If you want that, you will need some small microcontroller, for example running at 32768Hz, and some computer to set the right time
     
  11. wayneh

    Expert

    Sep 9, 2010
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    ... or a $4 timer from the hardware store. ;)
     
  12. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    Or one of several 4060 circuts that have been develops on this site. I didn't realize he wanted a alarm clock circuit. My bad, it was stated clearly.

    An alarm clock could also be modified for it. The buzzer used to trip a simple circuit.
     
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