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Light Dark sensor circuits and LTSpice simulation

Discussion in 'Renewable Energy' started by b.james, Apr 3, 2015.

  1. b.james

    b.james Member

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    If you need to build a dark detector and turn on or off a switch this might be a good way to do it . What do you think?

    MikeM drew it up so look at the final simulation

    http://www.electro-tech-online.com/threads/dark-detector.144195/page-2#post-1215803

    Post 33
    Testing this out it seems good from about 10 Volts through to 30 Volts . The resistor on the relay is only because its a 12 V relay and it gets hot so the extra resistor dissipates some heat . Take it out on 12 V olt systems
     
    Last edited: Apr 4, 2015
  2. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Why the new thread?
     
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  3. b.james

    b.james Member

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    Because this is particularly relevant to renewable energy. It consumes very little current , works on a wide voltage spread and is necessary for all night sensor lights . I wondered if I could put it in projects . Perhaps thats possible .or perhaps move the whole thing out of general and into here.
     
  4. dave

    Dave New Member

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  5. gary350

    gary350 Well-Known Member

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    Hum....dark detector. How about building a dark weapon. If you shine dark on the opposing army they could not see to shoot anyone. If the opposing army had your dark detector it could automatically turn on the lights so they could see. LOL.
     
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  6. b.james

    b.james Member

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    "Dark it be getting for moderators such as yourselves"
    He said "shineth the light" and they did deride and then ignore him.
     
  7. b.james

    b.james Member

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    A very useful sensor that keeps a relay on in the day with little power and turns off at night allowing NC relay contacts to make and power whatever.
    Here is DIy Layout creator pics for both Dark Sensor and Light Sensor
    MyLite.png DarkSensor.png
     

    Attached Files:

    Last edited: Apr 17, 2015
  8. b.james

    b.james Member

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    I bought a couple of these mentioned here
    http://www.eevblog.com/forum/reviews/light-sensor-controller/

    They seem to be pretty efficient although not adjustable easily and they pull the relay in at night so I will have to investigate if I can alter them to come on in daylight and off at night .

    The circuit in the above posts is by far superior on power use.
     
  9. Willen

    Willen Well-Known Member

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    I became fool three times, reading the post! Hehe

    Anyway, normal dark detector with single or two transistor has linear output so evening time, we get relay chattering problem. This one have square wave output, like an output from a comparator IC. I like the feature.
     
  10. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    • I have not seen any schematic yet, but without 30% hysteresis or so it is flawed.

    • % depends on load regulation of battery source during transition.

    • If threshold changes due to dip in V+ when relay turns on with negative feedback it chatters,
    • if positive feedback by inversion of reference amp and source signals then it has hysteresis.
    Solar level drops over 5 decades so 1/3 decade is not much.
     
  11. Willen

    Willen Well-Known Member

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    OP 'b.james' have posted a link theree in post #1. 1st page of the link, there are two nice schematic with LTspice simulation by 'alec_t' and by 'MikeMl'. Schematic by MikeMl seems simple because of just two pieces of transistor, output on simulation seems totally square ON and OFF.
     
  12. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Simulation and real test may not be same. Just saying unless there is hysteresis, it can toggle easily under some conditions.
     
  13. Willen

    Willen Well-Known Member

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    Hi, Just now I made the dark detector (http://www.electro-tech-online.com/attachments/39a-gif.92641/) designed by MikeMi (12V version) which is hysterisis! I never thought that with just two transistor I will get such very nice non-linear output! It's working from 4V to 15V or max. For 4V I used a LED as a load and it's ON and OFF is so impressive! Before I used to think that only comparator can do it! Amazing!
     

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