I am a newcomer and wish to ask about Diodes

Discussion in 'General Electronics Chat' started by drewpolk, Oct 30, 2011.

  1. drewpolk

    Thread Starter New Member

    Oct 30, 2011
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    What would be a good Diode to afix to the positice wire between the load and 12Volt battery to step voltage down to 9 Volts? Thanks and please respond.
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    To determine if this is an option at all we need to know the amount of current you want to draw and also if this current is variable or fixed.
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Can you also tell us how much the 12V input may vary, and how much variation can be accepted in the 9V output.

    Dropping voltage with a diode or diodes in series with a supply is not always a good solution, although it is sometimes acceptable.
     
  4. drewpolk

    Thread Starter New Member

    Oct 30, 2011
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    The current draw is very small since the application is for a trail camera which will only demand when triggered from the motion detector. I read in camera specs is 750 milliamps. Thank you and please respond. Drew
     
  5. debjit625

    Well-Known Member

    Apr 17, 2010
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    750 milliamps is not very small...use a linear regulator ,of course its not the best solution ,but for a beginner it will be easy...remember if you use linear regulator their will be a power loss ,if it is not be acceptable then use switching regulator but its circuitry will be complex.

    Good luck
     
  6. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The fact that your load is a camera pretty much rules out the simple (and risky) diode dropper. The camera may not be very tolerant of voltage fluctuation, and if you get this wrong it could be an expensive mistake.

    The situation is even worse if the camera only draws current intermittently, as the diode drop will be reduced or eliminated, depending how much (if any) standby current there may. You could add a dummy drain, but that would run the batteries down faster (assuming this runs from batteries).

    When selecting a regulator, bear in mind the minimum drop-out voltage, ie the difference between the input "12V" and the required 9V. If the 12V comes from a battery, you must allow for the minimum battery voltage when discharged. Depending on what kind of battery is used, this may mean that you require a Low Drop Out (LDO) regulator.
     
    Last edited: Oct 30, 2011
  7. samin

    Member

    Oct 14, 2011
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    Silicon diodes drop .6 to 0.7 volts, so I think if you series 4 diodes (.6v * 4) = ~2.4v but if you parallel them for current-handling they may not share the current flow equally.

    Anyway why not use LM7810 !
    one component. with 3 leads: ground, in,out.
     
  8. Adjuster

    Well-Known Member

    Dec 26, 2010
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    I think it would be better to use LM7809, which is a 9V part: 7810 is 10V. It is only just rated for 1A though, which is a bit close to the OPs 750mA estimate for his camera current drain. http://www.fairchildsemi.com/ds/LM/LM7809.pdf
     
    samin likes this.
  9. samin

    Member

    Oct 14, 2011
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    Yeah, If he can find one that can handle higher current, it would be better.:)
     
  10. drewpolk

    Thread Starter New Member

    Oct 30, 2011
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    So if the current is not always same it is now my understanding that a LOD Regulator will best serve the 9V requirement for the Moultrie D50 trail Camera? Actually it does run off of 6 Dcell alkaline batteries very well until temperature falls into the 40's F. or cooler. My thoughts are to connect a 12V. ATV battery with a solar panel trickle charge for long term outdoor exposure is draining the battery. The latest reply sounds like a simple version and easy to install in line from the battery to the camera and as stated from Adjuster, the LM7809 seems a good fit with 3 Leads. Thanks Samir and Adjuster for your insight for this project. Drew
     
  11. drewpolk

    Thread Starter New Member

    Oct 30, 2011
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    Thanks again! I could not identify where you add thanks to the post.
     
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