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Voltage Regulator

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  • Voltage Regulator

    Does anyone know of any small device that can regulate house current at an outlet ? If my projector runs at 115 v and the house current output is 125V , I would like a device that plugs into the house outlet and I could then plug the projector into the device to get 115v output to optimize correct projector running speed and extend bulb life.

  • #2
    Hi Thomas,

    I assume there is no 125V tap on your machine's transformer?

    Otherwise, if the machine is set up to run at 115V and you run it from 125, you should be OK. 115V is a nominal and the real voltage at the plug is quite changeable. Anything that plugs in has to be able to deal with this. Probably the biggest difference you would run into is the bulbs will burn a little brighter and burn out a little sooner.

    Things like sound boards probably don't care a whole lot about the difference in voltage and where it would make a difference, they should have on-board voltage regulators.

    Motor speed is mostly dictated by line frequency if it's an AC motor and should be internally speed regulated if it's a DC motor.

    Maybe you could find some sort of transformer with taps for 115V and 125V operation or even a continuously variable output voltage, but you could buy a whole pile of spare lamps for what one of these would cost.
    Last edited by Steve Klare; June 20, 2021, 11:27 AM.

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    • #3
      Hi Thomas,

      If you need a perfect voltage, with pure frequency, I suggest you a UPS (Uninterruptible Power Supply) , this is an inverter coupled with batteries.

      A good range of power available, price directly depends on power available.

      I have got a small one , however lead batteries are dead : To Understand batteries are time limited (mines were out of order 8 years later)

      Anyway, very popular for powering computers.

      It can be controled from a computer .

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      • #4
        personalli i wouldn't bother with only 10 volt difference, old projector usually dont have delicate electronics so they can cope fine

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        • #5
          As noted above, voltage ratings on appliances & electronics are typically nominal and slight variations will will have negligible effects on performance. These days, the alternating current standard for North America is 120V, 60Hz. In most of the rest of the world, it is 230V, 50Hz. Many modern devices can automatically sense and switch between the two systems. Others may have a two-position slide switch to select between them.

          Most vintage equipment was designed to only operate on one system or the other. Older devices made for the American market may be labeled for 110V, 115V, or 120V, but differences of up to several percent are unlikely to cause problems, as long as the household voltage remains constant. When voltage levels drop below 100V or exceed 130V, problems may occur.

          Regarding bulb life, the increased filament temperature resulting from a slightly higher voltage is probably insignificant compared to other factors that can shorten bulb life, such as physical vibrations and simply turning it on and off. The greatest shock experienced by a typical incandescent bulb is the sudden filament temperature spike that occurs when a cold bulb is first turned on. This is why failing light bulbs often blow at the moment you switch them on.

          Phil's suggestion to use an UPS can certainly be worthwhile, especially if your local voltage tends to fluctuate or sag, or if you experience frequent outages. If your goal is to maximize the life of expensive projector bulbs, you might want to ensure the UPS unit you buy produces a pure sine wave output. Many of the UPS units sold at the big box stores, warehouse clubs, and on Amazon produce a simulated sine wave output, as these are less expensive to manufacture.

          Instead of generating a pure sine wave, low-cost UPS units produce an output consisting of stepped square waves that approximate the shape of a true sine wave. If your equipment has an electronic power supply with good voltage regulation circuitry, this isn't usually an issue—I've been using these units to protect my home computers and hi-fi components for many years. This might not hold as true, however, for a vintage projector whose bulb and motors run directly off of line voltage.

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          • #6
            A lot of our machines have AC motors and they are really looking for something at least close to a sine wave: nice, continuous slopes. Years ago I had an 120VAC inverter (Radio Shack!) and the output was just a square wave: the word on AC motors was a simple "no!". I think anything reactive enough wouldn't take too long to blast the transistors in the inverter.

            My new one is pure sine wave: the word is "go ahead!". I've never tried it with a projector, but if there is ever another Hurricane Sandy, it just might happen.

            We have big Toshiba UPSs where I work: 6kVA and 30 kVA. Beautiful looking sine-waves, and 3 Phase on the big guys. We have even bigger ones than these, but I don't work on them.

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            • #7
              The 600W inverter I have is described as "Modified Sine Wave" as I don't have access to an oscilloscope now I can't check what it actually gives out. In the 1970-80s when I worked in telecoms the (then called No Break Power Supplies we had were two diesel motor generator sets with a centrifugal or magnetic clutch between them. The generator working as a motor with a flywheel when the mains was good. When the frequency went down the diesel was started and when it matched the revs of the generator the clutch engaged for it to power the store and forward message computer (two units discrete transistor logic with magnetic core memory drum, disc and tape storage) and its associated air conditioning. I think it must have been in the megawatt range overall, two other standard motor generator sets coped with the lighting and other building needs.

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              • #8
                It's probably a series of steps in voltage up and down: the more steps the better, of course.

                The UPSs I work on drive critical data sources, so that when the power goes down the machine can come to a safe stop and recover in minutes instead of days once the power returns. These are all an input section driving a bulk (capacitive) voltage, charging the batteries and powering the inverter input. When the AC line fails, the charger reverses current flow, charges the bulk and keeps the inverter in business. These stay on line for months and years at a time.

                The most critical stuff has the UPS inputs on diesel generators via automatic transfer switches. (They don't let me play with these!)

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