Mini LED panel Voltmeter connections

Discussion in 'The Projects Forum' started by Max12345, Oct 19, 2013.

  1. Max12345

    Thread Starter Member

    Aug 27, 2013
    63
    0
    Greetings
    The first link is the one I have purchased. The second link just has more photos of the same item, but with Red LEDs.

    http://www.ebay.com/itm/DC-0V-99-9V-3-wire-Mini-Blue-LED-Panel-Meter-Digital-Voltmeter-/121195040045




    http://www.ebay.com/itm/Red-LED-Panel-Meter-Mini-Digital-Voltmeter-DC-0V-To-99-9V-AT66-US17-NEW-CHEAP-/261306423512?pt=LH_DefaultDomain_0&hash=item3cd71398d8




    I have purchased a mini 0V-99.9V DC Blue LED panel mount voltmeter which I have not received yet. I wish to use it on my power supply.
    I have mailed the seller (in China) for a spec sheet, but I am not holding my breath.
    Has anybody used this meter before?
    Do you know or have the specs?
    I would like to know whether it uses the same power supply that it measures or whether it should have its own isolated power supply. Is there a schematic available to do this if required?
    Thanks
    Max
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    it says it needs its own power supply
    "Power supply range: 4V-30V"

    It has 3 wires..
    1 ground ground
    1 power supply+ wire
    1 measurement voltage wire
     
  3. Metalmann

    Active Member

    Dec 8, 2012
    700
    223
    Those little meters, are cheap and very accurate.
     
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  4. Max12345

    Thread Starter Member

    Aug 27, 2013
    63
    0
    So it's not a completely isolated separate power supply for the meter, as it will share a common ground with the actual power supply?

    Does this mean I should or can tap the meter's supply off the actual power supply? I'm unsure as to how to do a dual supply. Can you point me to a link please?

    Thanks
    Max
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,394
    1,606
    Yep, they share grounds.

    The meter needs 4 volts to run itself, so if your P/S can adjust to zero you can't connect the power and sense wires, is will not work below the 4 volts

    BUT... if you have access to the full supply you may well have a good point to tap, like the cap bank itself.

    For a single supply you put:
    +meter power to +P/S cap bank
    -meter power to +P/S return
    meter sense to +P/S output


    For a dual supply you put:
    (+ side the same)

    +meter power to -P/S return
    -meter power to -P/S cap bank
    meter sense to -P/S output
     
  6. Max12345

    Thread Starter Member

    Aug 27, 2013
    63
    0
    Hi ErnieM
    Like this? As shown in the attachment? Is this OK?
    Thanks
    Max
     
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    1,606
    Ahh, sorry I had assumed you were doing a +/- supply, not just a +

    Yes, what you drew looks correct.

    Since your transformer secondaries are separated, you can join them back together to make each one either a positive or a negative voltage (with respect to some common or ground).
     
  8. Max12345

    Thread Starter Member

    Aug 27, 2013
    63
    0
    Hi ErnieM
    I have to wait 6 weeks for the meter, so I don't want anything bad to happen to it, so just to be sure of the whole circuit, I posted it as an attachment for your perusal.

    Thanks so much
    Max
     
  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,394
    1,606
    Yes that looks like a good way to connect everything.
     
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