Can this circuit be used as sunlight sensor

Discussion in 'The Projects Forum' started by mrudul, Jan 23, 2011.

  1. mrudul

    Thread Starter New Member

    Jul 25, 2010
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    [​IMG][​IMG]Hai everyone .... can this circuit be used as light meter....... If theis circuit has any errors can you please help me to correct it......
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Yes, but it has flaws. The op amp is biased in a linear mod. You need a Schmitt Trigger configuration, so it is either on/off, not outputting a linear voltage.
     
  3. mrudul

    Thread Starter New Member

    Jul 25, 2010
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    I am doing a project "Automatic plant watering system"
    this system checks the soil moisture using soil moisture sensor.If the moisture is less then it checks the rain parameter (i.e sunlight , temperature , humidity , pressure) of the atmosphere.While searching for Light sensor ..i got this pdf. i want to know that this circuit better or not.... I am even posting the circuit diagram of Light meter. Please check that to.................now I am facing a problem now that i am not getting the circuit diagram of atmosphere humidity sensor and atmospheric pressure sensor. I want the circuit diagram or the idea to design the circuit(WITHOUT SENSOR IC's) that the output signals should be in voltage .Can you help me out to make this project a success????????? Relpy fast.....Less time ............
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    I just looked at the link on the other thread. It does use a Schmitt Trigger. So the next question is, do you know what a Schmitt Trigger is? Do you understand why it is necessary? These are the questions you should have been asking on this thread instead of opening a new one.

    The reason it is necessary it you are feeding a transistor that turns a relay on or off. You turn turn the transistor partly on it will heat up badly, as will the relay to a slight degree. You need to feed this transistor a digital signal.
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I merged the threads, so the other information is now visible here.

    Bertus
     
  6. mrudul

    Thread Starter New Member

    Jul 25, 2010
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    I have posted another two circuits of light sensor. Can you please check and reply me plzzzz.......
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Drawing one might work, it has all the problems of your first post, but it is simple. I have drawn similar for other people. This is a case of try it and see (I'd build the circuit only before I got into fancy boxes).

    Your first post had all the parts to do it right, but were wired wrong. The above post is so simple that there is not much you can do with it if it doesn't work (and it probably will).

    The second drawing is an experiment, it will give you some idea how things work, but has no practical application that I can see.

    Please turn on the private mail in your profile, we need to talk.
     
  8. mrudul

    Thread Starter New Member

    Jul 25, 2010
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    My Email Id: <SNIP>
     
    Last edited by a moderator: Jan 24, 2011
  9. mrudul

    Thread Starter New Member

    Jul 25, 2010
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    Hai....
    In this diagram if i implement a LDR instead of the two probes will it can be converted in to a light meter..... And one more doubt is that LM3914 and LM3915 are the same.... plz reply.....
     
  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Yes, you can alter it to measure light.

    [​IMG]

    As for the LM3914 versus LM3915 question:
    LM3914 is lineair, all steps are the same.
    LM3915 is logaritmic, all steps are 3 dB.

    Bertus
     
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  11. mrudul

    Thread Starter New Member

    Jul 25, 2010
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    hai ,
    In the above diagram the transformer used delivers 200mA but the transformer which i am having is of 1.5 A . how can modify it to get 200mA .
     
  12. bdd4

    New Member

    Jan 27, 2011
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    I looks like it will work to turn on the relay when some light falls on the LDR.. Since you have not given values for the bias and it could be a low voltage it would be idea to install a capacitor from the minus terminal to ground to prevent noise from triggering the circuit.

     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    If the voltage is correct, you do not need to change anything.
    The circuit will "draw" 200 mA of current from the powersupply.

    Bertus
     
  14. mrudul

    Thread Starter New Member

    Jul 25, 2010
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    Can i take an input to the microcontroller ??? if yes then from which point i should take the input to the microcontroller.........????????
     
  15. mrudul

    Thread Starter New Member

    Jul 25, 2010
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    hai ,
    I am now here for my friend he has designed a robotic arm but having the idea of lifting the lifting . the weighs around 750gms and he wants the arm to lift the things which it grabs which weighs between 300 to 500 gms .what should be the torque of the motor to be used in the arm ???????? and can you suggest any ideas for lifting .....
     
  16. mrudul

    Thread Starter New Member

    Jul 25, 2010
    26
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    Hai, i have constructed a simple light sensor using ldr, the output is amplified and given to micro-controller. I want to calibrate the sensor but i dont know how to calibrate the sensor. Can you help me to calibrate it?
     
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