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Measuring Frequency of stroboscope/strobe light

  1. Mar 11, 2007 #1
    1. The problem statement, all variables and given/known data

    I want to know how to measure the frequency of a stroboscope by using an LDR and picoscope, but i'm not sure what circuit I should make up with the LDR in order for picoscope to show the frequency.

    2. Relevant equations

    3. The attempt at a solution

    I thought connecting the LDR straight to the picoscope would do, but my teacher said it wouldn't work.
  2. jcsd
  3. Mar 11, 2007 #2


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    Gold Member

    Connect the LDR in series with a resistor, across the supply. As the resistance of the LDR changes, the voltage at the junction of the LDR and the resistor will vary. This signal you can put into another instrument.

    Code (Text):

    ---------------------------- + 5V
                   x  <- LDR
                   o-------------- > signal              
                   x  <- resistor
    --------------------------------- GND

  4. Mar 11, 2007 #3


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    Science Advisor
    Homework Helper

    Look up the data sheet for your LDR to find out what its "dark" and "light" resistance is, and what the safe voltage and current limits are. Then choose a suitable value of the fixed resistor. If the resistance is too small or too big, you won't get much change of voltage across it.

    BTW 5V seems a reasonable guess for a safe supply voltage, but checking the facts is always better than guessing.
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