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automatic dark sensor

Discussion in 'Sensors and Actuators' started by antsoua, Apr 20, 2015.

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  1. antsoua

    antsoua

    3
    0
    Apr 20, 2015
    Hi, please help! I would like to make an automatic dark sensor using AC(220v), the lamp has a bridge diode included, can this circuit works perflecly with the corresponding values? yur dark sensor.png
     
  2. davenn

    davenn Moderator

    13,589
    1,872
    Sep 5, 2009
    no
    that is VERY dangerous
    use a low voltage source for the LDR and transistor circuitry and use it to switch a 220VAC rated relay or preferably a SSR ( Solid State Relay)
     
  3. antsoua

    antsoua

    3
    0
    Apr 20, 2015
    I've tried to seperate both circuits by using an optocoupler and a 9v DC for the switching circuit! Is the configuration and values of this OK?

    Screenshot_2015-04-20-14-34-47.jpg
     
    Last edited by a moderator: Apr 20, 2015
  4. antsoua

    antsoua

    3
    0
    Apr 20, 2015
    PLEASE NEED HELD!!

    Automatic Night Light (outdoor)

    1- my 5watt 68k resistor heats too much! i have tried to lower the heat by putting 3 of the 5w 68k in series, that was ok! however when i connect the load the output voltage dropped!! please what what can i do to settle it?

    2- my second issue is the HYSTERISIS, the system is not able to actuate the relay

    diagrama_luz.jpg
     
  5. Alec_t

    Alec_t

    2,824
    756
    Jul 7, 2015
    That is a potentially DANGEROUS circuit which could kill someone. It also has errors. You should use an isolation transformer.
     
    duke37 likes this.
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
    This circuit again works directly from mains. As @davenn said, this is dangerous. Your post #3 shows a much safer configuration. You'll have to add hysteresis to avoid blinking of the light at dusk and dawn.
    Have a look at this circuit.
     
    Last edited by a moderator: Aug 29, 2015
    davenn likes this.
  7. duke37

    duke37

    5,361
    767
    Jan 9, 2011
    A resistor across C2 will dump some of the input current and reduce the dissipation in R3 and the Zener.
    Replacing R6 with a Zener will increase the amplifier gain.
    Investigate the effect of R5 and R7 to get it to operate the switch.

    Do your experiments with a 9V battery.
    I do not see the purpose of R4.
    I see no hysteresis although some would be a good thing to give a snap action.

    Some data on the optoisolator would be helpful.
     
    davenn likes this.
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