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Unregulated power supplies

Discussion in 'General Electronics Discussion' started by MyDog8em, Jun 6, 2013.

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  1. MyDog8em

    MyDog8em

    3
    0
    Jun 6, 2013
    Hello and thanks in advance for your time. I have a question about the above. I am putting together one of those nixie tube clock kits and I'm almost done. The kit says it requires a general wall wart 9 VDC/1A power supply. I know its potentially normal for these types to meter higher than the rated with no load but it makes me nervous to know that a 9 VDC unit like I have to meter almost 17 VDC and then plan on using it for this clock for 24/7 use :eek: . I also have a 6 VDC/1.2A unreg. unit that meters 10.5 VDC with no load. Will it be safe to use either or or better to use one or the other of these units?

    Thanks again.
    Mike.
     
  2. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    The 6V supply would almost certainly be safe but the voltage may drop too low under load.

    The 9V supply looks dodgy but could be used with an added-on regulator (LM317T) which will need a substantial heat sink.
     
  3. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Does the kit have a regualtor or it's own, or the is the incoming 9V used as is?

    Bob
     
    AnalogKid likes this.
  4. MyDog8em

    MyDog8em

    3
    0
    Jun 6, 2013
    Thanks for your replies.

    @duke37: I did find a PS rated at 9 VDC/850ma that meters 14.8VDC no load, do you think this would be safer over time for this clock? The kit does recommend a 750ma to 1A. I was gonna try to shoot for the max output @ 1A but if 850ma will work, I'll feel better with that.

    @BobK: There is a regulator IC yet to be soldered on board, but I'm not sure of its limitations and theres no numbers on it. It looks similar to the attached (like the LM317T). Where this component is placed on the PCB is part of the mounting of the PCB to the clock case and there is no heat sink.

    [​IMG]
     
    Last edited: Jun 7, 2013
  5. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    Many things come in TO-220 style. This could be a 5V regulator which could overheat if the input voltage is too high. A circuit diagram would help.

    The higher the current capability of the wall wart, the cooler it will run.
     
  6. MyDog8em

    MyDog8em

    3
    0
    Jun 6, 2013
    I went ahead and bought a regulated PS for the clock. I'm sorry as I don't have a diagram immediately available but I really do appreciate all your help. Let me add that I'm no expert, but I know much of the basics. I have the kit completed and tested it with the original 6V ps that I spoke of and it seems to work but I intend to wait for the arrival of the correct ps to use it 24/7. Thank you again. You've been a huge help!
     
  7. Y2KEDDIE

    Y2KEDDIE

    259
    15
    Sep 23, 2012
    I hope I'm not considered a Hi jacker of this thread, but on the subject of unregulated supplies.........

    I've replaced a few gel-cell battery jump start packs and find a common problem. Most units come with a wall-wart power supply. I've checked many and most are putting out way more voltage than required due to non-regulation. This causes the battery to overcharge and slowly boil away the electrolyte. Most people tend to leave them charging 24/7, year after year.

    I've bought inexpensive u-processor contained battery maintainers and they seem to keep the battery more healthy
    : these are the type which monitor the battery voltage and control the charging current by pulsing.

    Rarely batteries don't last more than 2- 3 years when charged with wall -warts, mine are lasting 5+ years with the maintainers.

    Anyone else have similar experiences?
     
  8. AnalogKid

    AnalogKid

    2,501
    719
    Jun 10, 2015
    A proper gel cell charger has three output states. One is a low current to wake up the battery from long shelf storage or deep discharge. Next is the higher current main charge state. Once the battery terminal voltage hits a trip point, the charger drops down to a low current trickle charge state to keep the bettery topped off without overheating. LTC and others make single-chips that do all of the monitoring and management.

    ak
     
  9. Arouse1973

    Arouse1973 Adam

    5,165
    1,087
    Dec 18, 2013
    The problem I have had with battery chargers is when they are on load. If you speak to the charger manufactures they may tell you that a battery should be charged off load. I tend to agree. The problem with too larger load whilst charging a battery prevents the charger from going into maintenance mode and usually stays in float mode which gradually dries out the battery. We had several battery with early life failures and we replaced the battery charger with a PSU.

    Thought you might be interested.
    Adam
     
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