outdoor lamp control?

Discussion in 'The Projects Forum' started by sufi, Jan 24, 2010.

  1. sufi

    Thread Starter New Member

    Jan 23, 2010
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    Hello Bros i really want your help. I want to put signpost with a 12V lamp to glow only during night time and it will be powered by solar panel(max 20wp) and battery(12v lead acid ) .

    Is it advisable to use Microcontroller to switch ON at 6pm and OFF at 6am in the morning (i know it is a bit difficult to program the PIC)

    What about using simple sensor based switch?

    just tell me where to begin i will dig deep!!

    thanks in advance
     
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Which would you "prefer" year round: 6AM-6PM On-Off or dusk/dawn On-Off? Makes a difference if you're in Alaska or Brazil. either approach is very do-able.

    ken
     
    Last edited: Jan 24, 2010
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Would help if battery capacity & lamp draw is known. The panel will tell if it's light, detect at about 1/2 V. Detect low battery V, and shut off load, use charge controller or syenthized zenor to dump excess panel power. Look at All Electronics Cat # SCN-1, 3A controller $ US 17.00.
     
  4. whatsthatsmell

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    Oct 9, 2009
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  5. sufi

    Thread Starter New Member

    Jan 23, 2010
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  6. sufi

    Thread Starter New Member

    Jan 23, 2010
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    7w clf DC lamp and i select deep cycle solar battery (12v ,12Ah) so that
    low battery voltage is no more a threat.if the lamp lights for 10h
    it draws 70Wh or 5.83Ah or 50% of the fully charged battery .
    i use syethized zenor to dump excess panel power but as you said using
    controller is the best

    thanks
     
  7. KMoffett

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    Dec 19, 2007
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    I haven't been able to find a accurate, inexpensive (<$35) off the shelf 12HR-on/12Hr-off 12V timer. Or a simple circuit.

    Ken
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Using thr comparator reff-LM311 , LIGHT ACTIVATED RELAY [ LIGHT ] with 5 SECOND RELEASE DElAY, with small changes: solar panel replaces photo transistor, connected ahead of panel blocking diode, reverse IC 1A +_,replace 2N3906 with P ch MOSFET with about 2A rating. I'll try to draw up a sketch tomorrow. Panel might produce about 9 Ah- will be close.
     
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  9. KMoffett

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    Dec 19, 2007
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  10. KMoffett

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    Dec 19, 2007
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    OK, I bench tested this with a PCB I had pulled in the past, from a battery alarm clock. Up to the output of the 555, it works. The setup switch, 4013, and MOSFET are just the concept for toggling.

    Next, I'm going to get another alarm clock, and see if I can do this on an intact one. Keep your fingers crossed.

    Ken
     
    Last edited: Jan 27, 2010
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  11. Bernard

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    Aug 7, 2008
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    I'm going to have to dig into my clock box and try that. But for now here is sun rise ,lamp turn off ckt. A PNP high gain transiston, medium power, also OK with 20 mA base drive available. Adjust V divider 47k-10k for desired light or darkness.
     
  12. sufi

    Thread Starter New Member

    Jan 23, 2010
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    guys I really want to thank you! pround to have you there!
     
  13. KMoffett

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    Dec 19, 2007
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    Got a battery alarm clock at Goodwill. Started to disassemble it and found that the beeper was attached with wires, rather than on a PCB. Great...easy to rewire. But...as the case came apart a couple of gears slipped out of place. Now trying to reassemble it...#?/@% !!! :( If I could find an identical one I would know what "not to do". ;)

    ken
     
  14. sufi

    Thread Starter New Member

    Jan 23, 2010
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    Thanks once again Bernard,I was busy trying to understand everything and i have some question for you.The volt at pin 2(inverting pin) is 2.1v and to the best of my understanding the volt at pin 3 should be above 2.1v to stay 'OFF' ,which is possible at day time.But you know the voltage from panel depends on the number of cells the panel made ,for instance 20Wp panel has 36 cells and each cell generate on average 0.6v so you get ≈21v Voc at noon.If you cover only one of the cells the current becomes almost zero but the Voc does't vary a lot(16-18v) . i doubt it may not go below 2.1v at night(at least up to 7pm) so that the lamp turned on.I am waiting your sketch based on LM311.
    regards
     
  15. sufi

    Thread Starter New Member

    Jan 23, 2010
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    Thanks for everything but KMOffett is it possible to replace the clock function with something simple i can built for the same purpose? ts he pulse lasts for a minutes but what if i use timer just to start in?
    thanks in advance
     
  16. Bernard

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    Aug 7, 2008
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    Re pg 15: Doubt V will fall below 2.1V at night. Using 15 W panel, Feb. 10th, a few representative morning readings:
    Time V I-amps
    7:05 .49 -.01 sun on mountain top
    7:11 1.43 -.01
    7:23 2.24 0
    7:31 2.59 0 sun on top of wall
    8:08 6.28 .07 sun just touching panel
    8:22 15.0 .11 full sun no dew remaining OCkt
    12.0 .35 35 ohm load 4.2 W
    1:00 PM 15 .87 13.1 W peak power 22 V OC, 1.08 A SC
     
    Last edited: Mar 16, 2010
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