Voltage splitter recommendation

Discussion in 'General Electronics Chat' started by rsfoto, May 21, 2013.

  1. rsfoto

    Thread Starter Member

    May 14, 2013
    134
    1
    Hi,

    I have in my observatory some low voltage and very low amperage consumers which need constantly to be powered so they do not loose the setup information.

    Originally from the producer they come with batteries but as my setup is fix eg. I do not move the mounts anymore I decided to power them from 5V or 12V powerbricks, but as these consumers use only 3V I am doing it via a Trimpot as voltage splitter.

    Is there a more convenient way to do it ? The Trimpot is 1K and it barely gets warm.

    I know I could use fixed value resistors but I was too lazy to calculate the values :rolleyes: . I first adjust it with no load and then I adjust the voltage under load.

    Thanks for any suggestions :)

    [​IMG]
     
  2. Shagas

    Active Member

    May 13, 2013
    802
    74
    If I understand correctly then you are using a potential divider to give you 3volts from 5 or 12 volts .
    If that's the case then it's a pretty bad way of doing it .

    The easiest way of doing this would probably be to use a fixed voltage regulator.
    http://www.ti.com/lit/ds/symlink/lp2950-n.pdf for example.
    It's a small 3pin device . You connect 1 pin to ground , 1 pin to your positive terminal and 1 pin as the 3volt output .
    Or just go to your local electronics store and ask for a 3 volt voltage regulator .
     
    rsfoto likes this.
  3. rsfoto

    Thread Starter Member

    May 14, 2013
    134
    1
    Hi,

    Thanks a lot and yes that is why I asked.

    OK, my 2 devices so far are still working and the Trimpot has still not caught fire :D This sounds like an excuse which is not :)

    Will investigate and experiment with those devices

    Again thanks a lot
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    rsfoto likes this.
  5. rsfoto

    Thread Starter Member

    May 14, 2013
    134
    1
    HI,

    OK I measured the current the circuit for keeping the data is 12μA.

    Is that possible ?

    Would that be 0.105A per year. 0.000012 x 24hours x 365days because that is what normally lasts a battery in this devices ...

    and it uses a CR2032 which allegedly has 250mAh capacity

    I measured it with a Steren MUL-600 mutlimeter like this one

    http://www.sterenshopusa.com/catalog/prod.asp?p=2477

    After reading the datasheet of the LM317 I see that it draws 10mA for working whereas my trimpot version is using 5V / 1000 = 0.005 (5mA) and it is provided by an regulated power brick. So does it still make sense to use the LM317.

    I thought there could be a more less consuming solution. Now that I am writing this, ¿ could I use 100K Trimpot and so just consume 50μA and the device would still have enough current for working ?
     
    Last edited: May 23, 2013
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