NEED HELP! "easy" Photoresistor run servo project...

Discussion in 'The Projects Forum' started by Fox_911, Mar 16, 2017.

  1. Fox_911

    Thread Starter New Member

    Mar 16, 2017
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    Hi, Im very green to electronics and this "simple" project is getting the best of me. I want to run a servo off a tiny photoresistor and a 9v battery. I would like to keep everything as small as possible.

    Specs:
    The Photoresistor:
    - Min Voltage-150 volt DC
    -Max wattage 90 mW
    -spectral peak 540nm
    -Light resistance 0.5 Mohm
    -100 10:0.7 ??
    -Responsive time up:20 Down:30
    -Illumination resistance 4

    The Servo:
    -Current draw idle 6mA
    -Current draw stall 350mA
    -Voltage 4.8 - 8.5V

    Thanks for any help!!
    Best Regards, Justin
     
  2. DickCappels

    Moderator

    Aug 21, 2008
    4,863
    1,470
    Datasheet or part number and manufacturer of photoresistor please.
     
  3. LesJones

    Well-Known Member

    Jan 8, 2017
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    332
    Is the sevo one that you just reverse the supply polarity to reverse the direction or is it a model contol servo that is controlled by pulse length control ? I have never seen a photoresitor with a minimum voltage specification. are you sure 150 volts is NOT the maximum volltage rating ? If the 9 volt battery is a PP3 type it will not provide enough current. You will need a larger capacity battery. (For example 6 AA cells.)

    Les.
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Exactly what should the servo do in response to sensed light changes? Take up a position proportional to light brightness?
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    LDR specs. make no sense to me, just call it 2 meg. dark, 100 ohms light. Just using the U4 ckt. for the hobby type servo, substitute the LDR for R 11 & parallel LDR with 100 k pot. . & see what happens. Servo-control 00000.png
     
  6. Fox_911

    Thread Starter New Member

    Mar 16, 2017
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    That is all the info i have on this device. basically I want a light activated servo i just need to know the components i need to make it work. i want the device as small as possible, its for a drone application.
    Best Regards, Justin
     
  7. Fox_911

    Thread Starter New Member

    Mar 16, 2017
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    Thanks for the response! this is a rc servo so yes as i understand its a pulse length control. and you are right that was 150 max voltage. As far as the voltage ive seen this run on a 5v battery but not sure of the milliamps.
     
  8. Fox_911

    Thread Starter New Member

    Mar 16, 2017
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    0
     
  9. Fox_911

    Thread Starter New Member

    Mar 16, 2017
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    Thats what the manufacturer gave so that's all i have. basically I want a light activated servo i just need to know the components i need to make it work. i want the device as small as possible, its for a drone application.
    Thanks
     
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    I'd measure the resistance of the LDR, light, dark & over expected light operating conditions.
    I believe a 556 is available in surface mount, not sure of 555.
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Something based on this, perhaps?
    LDR-to-Servo.JPG
    This should drive a standard servo from one limit to the other when the LDR is in the dark or light respectively. Resistor values might need tweaking depending on the LDR characteristics.
     
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