LED output ...

Discussion in 'General Electronics Chat' started by rsfoto, Jun 11, 2013.

  1. rsfoto

    Thread Starter Member

    May 14, 2013
    134
    1
    ... on a telescope mount.

    Hi,

    I just got a telescope mount into which a Polar aligment scope can be installed. This Polarscopes do have a reticle which can be illuminated by a LED.

    Now the main board has a jack for the LED driving. I measured the output voltage of this Jack and it goes up to about 8V, but as I know a LED normally works up to maybe 3 to 3.3 volt.

    The hand controller of the telescope mount has in its function menu the possibility to adjust the LED intensity.

    Due to the high voltage I assume that the main board controls the LED intensity by limiting the current. Is that possible ?

    Thanks :)
     
  2. WBahn

    Moderator

    Mar 31, 2012
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    4,788
    Does the LED (and LED alone, no other circuitry components at all) plug directly into this jack?

    Yes, the main board may well control the LED intensity by any number of means. One of them is to adjust the voltage in order to achieve a desired current (and when nothing is plugged it is goes to maximum voltage). Another is to pulse the output full-on and full-off and vary the amount of time it spends in each state in order to vary the average current.

    There is very likely a current limiting resistor on the main board but since you are measuring the voltage without drawing any current, its presence isn't seen.
     
    rsfoto likes this.
  3. rsfoto

    Thread Starter Member

    May 14, 2013
    134
    1
    Thank You. Yes only a LED is plugged into that Jack and nothing else and with the handcontroller you can adjust the intensity of the LED.

    Again thanks for the explanation.

    So an easy test is to take a LED and plug it into the Jack and see what happens. Apart from blowing up the LED nothing else should happen, I assume :eek:
     
  4. WBahn

    Moderator

    Mar 31, 2012
    17,720
    4,788
    I would imagine that would be okay.
     
    rsfoto likes this.
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