Is 19v too much?

AndyH Jan 18, 2021

  1. AndyH

    AndyH TrainBoard Member

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    I've got a couple of 19v transformers of the right level of amperage, but is 19v too much for a dcc++ system? Track side of course, I know that it will cook the circuit board.

    Thanks

    Sent from my SM-N976B using Tapatalk
     
  2. AndyH

    AndyH TrainBoard Member

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    Using an L298n for programming and BTS7960B for main.

    And also an arduino mega and a normal arduino motor shield.

    Sent from my SM-N976B using Tapatalk
     
  3. Ash

    Ash TrainBoard Member

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  4. crusader27529

    crusader27529 TrainBoard Member

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    The NMRA DCC specification says the maximum voltage between 22v and 27v is acceptable, depending the scale you're using.

    The KA devices use serial connected super-capacitors (which are low voltage devices) to store a higher voltage. The B+ voltage supplied by the decoder is some percentage of the track voltage, so the KA needs to be compatible with the decoder and track voltages.
     
  5. Sumner

    Sumner TrainBoard Member

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    So what scale are you? If N the most I've seen recommended is about 14v and maybe 15-16 for HO,

    Sumner
     
  6. schufti

    schufti TrainBoard Member

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    unfortunately the question lacks some (important?) information:
    is it 19V ac from a transformer? Idle or loaded? or 19V from a laptop type powerbrick?
    19V idle from a transformer will give ~27V dc after rectifier/electrolytic, just maxing out the specification.
    19V under load (higher in idle) may pose a threat to even the booster.
    19V dc will be fine with most of the equipment as there is usually some voltage drop in the booster.
     
    BigJake likes this.
  7. wvgca

    wvgca TrainBoard Member

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    i ran 18 volt off the transformer [unloaded] to be on the safe side ...
    this was HO and for DCC ++
     
  8. BigJake

    BigJake TrainBoard Member

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    If from the transformer (i.e. 19VAC), then it also matters how the AC voltage is specified: RMS, Peak, or Peak-Peak. Most meters will measure either true RMS*, or something scaled to RMS* for a good sinusoidal waveform. If measuring on an oscilloscope, then it is likely either Peak (top of the wave to mid point or ground) or top to bottom (peak to valley), unless it was converted mathematically, whether by hand or as a function on the 'scope.

    * Within frequency limitations of the meter, but an AC-line-powered transformer will be easily within those. However, DCC waveforms are too fast and non-sinusoidal for most meters to provide accurate RMS voltage/current.
     

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