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Low voltage plug sizes

Discussion in 'Tech Talk - Gadgets, Gizmos and Technology' started by AntAltMike, Oct 13, 2011.

  1. Rich

    Rich DBSTalk Club DBSTalk Club

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    Max to me means the inrush current of any electrical device. Sustained current is the current it pulls when the inrush current subsides and the device runs as it should. The device is still the governing factor when it comes to amperage.

    Just ran around the house looking at devices with wallwarts (always wondered what they were called, learned something today) on them and only found one that doesn't have the amperage on it. Variable speed screwdriver that just says "6V" on it. Guess it's because it's a variable speed device, but there is no amperage rating on the driver itself.

    This is really making me wonder how many plug sizes actually exist. Never gave it much thought since I've always worked with much higher voltages. Very interesting.

    Rich
     
  2. Rich

    Rich DBSTalk Club DBSTalk Club

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    Is that an NEC standard?

    Rich
     
  3. P Smith

    P Smith Mr. FixAnything

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    No, not inrush current - modern switching PS handle it different way.
    Max is mean the PS will work certain amount time, could become hot but will handle the load. Sustain will be for indefinite amount of time.

    No, not NEC.
     
  4. houskamp

    houskamp Active Member

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    biggest problem is there is no standard for small stuff.. they use whatever voltage, current, plug size/type they want to.. they are required to be marked in some way.
     
  5. Rich

    Rich DBSTalk Club DBSTalk Club

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    Considering how everything over 110VAC is regulated, I find that rather amazing. No regulation whatsoever? This is turning into a real "eye-opener" for me.

    Rich
     
  6. Rich

    Rich DBSTalk Club DBSTalk Club

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    Max means you can run it at an amperage that will eventually cause it to ignite? Please tell me they have thermal protection built into them.

    I can find no devices in my home that have "Max Amperage" and "Sustainable Amperage" on them.

    Rich
     
  7. AntAltMike

    AntAltMike Hall Of Fame

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    I'm not an electrician, but I think that everything over 60 volts is regulated as a certain classes of wiring that professional licensing for service. I think under 60 volts is "Class B" wiring and there is little regulation of it. That has resulted in some regulatory "gray areas", like with 70,7 volt ceiling speaker wiring, and now, 90 volt AV cable TV trunkline powering.

    I once had to get a "Class B" wiring license for a C-band satellite installation. The local electrical inspector actually came out to confirm that the mast and coax were grounded according to the 1987 NEC. The code said that "the mast" had to be grounded, and he wouldn't allow me to satisfy that requirement by grounding the mast mounting bracket. I had to drill and tap a threaded hole for a grounding wire connection screw.

    The code also said that the outer conductor of the coax downlead had to be grounded with a wire "approximately equal in current carrying capability to the coax outer conductor". Unfortunately, there are no published specs for that, and since high frequency current flows on the outside of the conductor, one could plausibly ague that I would need a copper ground wire equal in diameter to the coax, which would have ben about 0000. He did say that since an auxiliary ground rod could be bonded with 6 gauge wire, it would make no sense for a system to require ground wire any larger than that because the ground path capacity would be limited by its weakest link, so he OK-ed the use of 6 gauge ground wire for that purpose.

    The Code regulations are for fire and shock prevention. They don't care about damage to components or suitable performance.

    One reason that many 110 volt line powered devices use wallwart and desktop supplies is so that the manufacturers will not have to get UL approval for each variation of the product. They only need to get the external power supply approved.
     
  8. Rich

    Rich DBSTalk Club DBSTalk Club

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    I am an electrician and I'm having a hard time with this, but I find it very interesting. Grounding, as you've found out, is a royal PITA, open to differing opinions in different jurisdictions by different officials.

    In industrial environments, low voltage is considered anything under 600VAC. Voltages above that are really just plain scary. I was qualified to work on 4160 and I avoided that as much as possible. Any devices that were under 110VAC were installed and serviced by our "Instrument Men". A group that knew little about electricity. We had a strong union that kept the various crafts well separated and I rarely had anything to do with those very low voltages. Which made me happy, because, as I've mentioned many times, I'm very lazy....:lol:

    I really find this discussion about "wallwarts" very interesting. I hope it continues.

    Rich
     
  9. P Smith

    P Smith Mr. FixAnything

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    You could find them in UL docs.
     
  10. houskamp

    houskamp Active Member

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    One of the main reason for wallworts it that the regulations end at the wallwort.. much easier to get devices approved..
     
  11. Rich

    Rich DBSTalk Club DBSTalk Club

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    You don't think I'm actually gonna search for UL documents, do you, Pete? You gotta keep in mind how LAZY I am!

    Rich
     
  12. Rich

    Rich DBSTalk Club DBSTalk Club

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    So, the only way to be sure you're not gonna incinerate the WW is to use one that has a higher amperage rating than the device requires? If the plug fits. I really find all this rather unbelievable (I don't doubt anyone, just kinda surprised). No one regulates these things?

    You can actually stick a 7V WW on a device that calls for 2Vs if the plug fits? Wouldn't that be like putting 220VAC into a 120VAC motor (which will promptly burn, if the thermal device in it fails)?

    Rich
     
  13. AntAltMike

    AntAltMike Hall Of Fame

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    Any wall power supply will have a non-replaceable fuse on its input size -typically under 0.5 amps - which makes it impossible for it to draw enough current to start a fire. On the output side, a primitive linear supply will have its output voltage drop to near nothing when shorted, as it's theoretical maximum output current would be limited by the impedance of the secondary coil, whereas with switching supplies, I shorted a two amp one recently without damaging it, so whether it had a thermal sensor or some kind of current draw sensor, I don't know, but it didn't fry anything.
     
  14. AntAltMike

    AntAltMike Hall Of Fame

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    You've go it! When these push-in plugs came into common use in the 1990s, I really expected some industry group to do something to standardize them, but no one did.
     
  15. Rich

    Rich DBSTalk Club DBSTalk Club

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    Don't understand. If you're drawing 2 amps, how does a .5 fuse not blow? I really don't understand how these things work.

    Rich
     
  16. AntAltMike

    AntAltMike Hall Of Fame

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    V x A = W
     
  17. P Smith

    P Smith Mr. FixAnything

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    input: 110Vx0.5A (max) = 55W (max)
    output: 5Vx2A = 10W
     
  18. TBoneit

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    P Smith beat me to it
     
  19. Rich

    Rich DBSTalk Club DBSTalk Club

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    OK, formulas I have no problem with, but what's the load that the .5 fuse is protecting, physically, I mean?

    Rich
     
  20. P Smith

    P Smith Mr. FixAnything

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    in case of input over-voltage (240VAC) and other possible shorts inside of the PS what would over-load first contour (AC), include second contour (DC)
     

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