Automatic Light Dimmer

Discussion in 'The Projects Forum' started by Nara Shikamaru, Mar 22, 2008.

  1. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
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    Hey everybody!!....i want to do an experiment at my house!, i want to do an Automatic Light Dimmer!!.....that regulates itself with the ambient light, i want to automatize ten(10) 120VAC light bulbs!!........the circuit that i have, i got i from "Home Remote Control & Automation Projects" by Delton Horn but i Cant do it because it uses a X9503 digital potenciometer!!.....the problem is that here in venezuela they dont sell it!!.....so does anyone has a Schematic that could pass me??.....i havent been able to find a circuit over internet.....thanks a lot!!
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    So if I understand your request correctly, what you need is something that you can use as a substitute for the X9503 that you can obtain locally in your country?

    hgmjr
     
  3. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
    92
    3
    that could be a solution!!...thanks!!.....or does somebody has another schematic that works in a different way that could pass me....cause over the inernet i cant find anything....
     
  4. rwmoekoe

    Active Member

    Mar 1, 2007
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  5. hgmjr

    Moderator

    Jan 28, 2005
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    I think the reason he is trying to avoid purchasing the parts he needs online is because there are severe trade restraints placed on such purchases in his country.

    hgmjr
     
  6. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
    92
    3
    Hey hgmjr!!.....whoa!! you`re totally aware of the "commies" policys in my country right now!!......thats right!!.....you got to pass a lot of burocratic permises to buy online......thats why i must stick to the electronics shops here!!........

    thats why i was wondering if you would have another schematic that you could pass me, or another schematic on the internet!!.....thanks!!
     
  7. hgmjr

    Moderator

    Jan 28, 2005
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    Do you have a sketch of the circuit you are presently proposing to build? I am referring to the circuit that uses the digital potentiometer that you cannot easily obtain.

    hgmjr
     
  8. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
    92
    3
    this is the circuit!!......i use the Proteus Isis Circuit Simulator for the schematic, in that simulator it doesnt have digital potenciometers....so i showed there how the path get to the X9503 and then they go to the optocoupler to the power section.....the part with the amplifier you can see the LDR simbolize as a potenciometer........
     
  9. hgmjr

    Moderator

    Jan 28, 2005
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    Greetings nara,

    I hope you don't mind that I took the liberty of attaching a pdf version of your schematic. Some of our more cautious members are averse to opening Word documents due to the possiblity that they may be virus infected. A pdf is less threatening and so will be more likely to be viewed by the community at large.

    hgmjr
     
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  10. hgmjr

    Moderator

    Jan 28, 2005
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    Ooopsss! I almost forgot. Thanks for providing the schematic. That should grease the wheel to a solution nicely.

    hgmjr
     
  11. hgmjr

    Moderator

    Jan 28, 2005
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    Looking at the schematic, I see the LDR and the opamp used as a comparator to determine whether the digital pot is incremented or decremented by the 555 timer.

    Pretty nifty little circuit.

    hgmjr
     
  12. hgmjr

    Moderator

    Jan 28, 2005
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    Is it possible that you have access to a digital potentiometer from another manufacturer? The one being used is one of the simpler interfaced digital pots so there is a good possibility you could locate one that is equivalent.

    hgmjr
     
  13. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
    92
    3
    Whoa Thanks a lot Hg!!.......electronics shops here have the standard common devices....digital potenciometers like that they dont sell it......the only digital potenciometer available must be used with PIC......do you have an idea of how to do an "adaptation" of that circuit using it like that and doing something else for that part?....or maybe another circuit?......thank you so much for your help!!
     
  14. hgmjr

    Moderator

    Jan 28, 2005
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    That's a bummer!

    I will try to think of something to substitute for the digital pot in an effort to preserve the components you already have access to. The one that is used with the PIC probably uses the SPI communication scheme.

    In the meantime, other members may be able to come up with a workaround that can get you going.

    hgmjr
     
  15. hgmjr

    Moderator

    Jan 28, 2005
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    Do you already have the 555 timer purchased? If so, what is the exact part number on the device. I am interested to know if it is of the bipolar or cmos type. I should be able to tell by knowing the part number.

    hgmjr
     
  16. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
    92
    3
    Yeah!! dont worry!....the electronic shops have thousands of components!!....but digital potenciometers they dont import cause nobody uses them......but the usual components you can find them......555 i have two versions.......NE555N and TA7555P......
     
  17. hgmjr

    Moderator

    Jan 28, 2005
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    OK, here is what I'm thinking.

    It is just possible that you can use the circuitry you have in your schematic with a little rearranging. The 555 timer is already generating a ramp. Perhaps it can be used as a ramp generator. This ramp would then feed the reference pin of your opamp being used as a comparator to produce a PWM signal at the output of the LM324. This duty-cycle would be a function of the voltage set by the LDR.

    The output of the LM324 would need to feed through an RC-integrator that would then set the current in the photo-diode using a voltage to current conversion circuit possibly in the form of a current mirror circuit.

    Do you follow my line of thinking?

    hgmjr
     
  18. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
  19. hgmjr

    Moderator

    Jan 28, 2005
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    Unfortunately, sgtwookie, nara lives in Venezuela where access to parts via Internet is heavily regulated and generally discouraged through trade sanctions.

    I think this is a good opportunity to tell you sgtwookie, "Thank you for your service to Our Country".

    hgmjr
     
  20. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    The schematic posted will not be able to do any dimminng at all, since it has a zero-cross detector to only switch on fully.
     
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