I was hoping someone could apply what you know to what I think I know here:

I'm preparing a power, uh, box, that will convert 208 volt three phase power to 240 volt three phase power so I can run some JBL Synthesis amps to be used overseas. I've got the step-up transformers needed to do that, and I'd like to have an idiot light to tell me that power is present. One light for each phase, that is.

At Home Depot they have 0.25 watt 120VAC LED lamps intended to replace present incandescent night light bulbs. Do you see any reason why these would not work by simply placing a resistor in series with them?

I suppose, which itself is an issue, that these LED lamps have a pretty good power factor, meaning that a resistor would come close to cutting the power in half. I intend to use the stated wattage and a goal voltage of 110 volts to determine the resistor value, and to size the resistor at one watt.

Do you foresee any problems with this?

Thanks!

what you talking bout willis? sounds dangerous? i like it. :)

im no electrician but you should be able to put one bulb between neutral and hot1 (120) the other bulb between neutral and hot2 (120). this would let you know each side of the 240 is operating.

Question: Where are you getting 208 3-phase power? The amps do not use 3 phase. They are 120volt from what I found.

208 is the wild leg to neutral in a typ. US 3 phase system.

Our test setup has 208 3 phase. It's what's for dinner. I mean, it's what's on the wall here in Southern California.

I've got amps designed for use overseas. They want to see 230 volts single phase. They've got dumb brute force power supplies, and 208 VAC is too low.

If you use one phase of a three phase supply, then you have single phase. I didn't mean to say that the amps use three phase power, but that we have three phases, and we will use each as a single phase, balancing draw as much as possible.

Believe it or not, the projector, which draws 23 amps at 208 VAC, can run on 200 to 250 volts. The low power units, those with small switching power supplies, can run on just about anything, so they are not an issue.

I'm using step-up transformers to convert 208 3 phase to 240 3 phase, using 2 of those phases for the power amps and the other phase for the projector. So, yeah, it will be three phase in and three phase out. This mirrors the power available to us in Saudi, except they use a delta and we have Y. We're using EquiTech transformers anyway, so that will be dealt with.




Anybody have an answer about the LED?

Yes and no. The 208v "wild" leg is generally found in US commercial installations that use a 240v "Delta" configuration. In my experience, this is much less common than the "wye" configuration, 208v 3 phase.

Check out this webpage: [Link: programmablepower.org]

As to the original question, how about putting 2 of these LED bulbs in series? No muss, no fuss, nothing that would make an inspector look twice.

Good luck!

JIM BATES

Put two globes in series and use them as a voltage divider. 120V each.

the 208 and 277vac are generally used for lighting loads in commercial buildings

I would also be careful to look at the incomming frequency requirement.
Most european systems use 50 Hz and we use 60 Hz. you could cause considerable damage to these units if the frequency is ignored!

Found a solution for you.

[Link: marcspages.co.uk]

Ernie,

You certainly should have no problem adding a resistor.

If the power factor were not good, I would cause a problem. The only issue that could cause the power factor to be much off, would be that the forward voltage drop of a white LED is about 3.6V. So as the line voltage gets below 7.2V, the current will drop more than you'd expect, and will drop to zero somewhere a bit below 3.6V. But, I expect this to cause very little power factor, so I believe you'll be fine.

Certainly another option, which may be simpler, is to put two bulbs in series. This should also work fine.

I thought this was such a simple question. The ENTIRE question is contained in the title of the thread: Can I run a 120 VAC LED light off of 240 volts? Forgetting that I since discovered that my conversion system will give me 230, not 240, that was it.


Thanks to those who addressed the question. I always appreciate it when people ask questions and give some background, as I'm experienced enough (and enough of a smartass) to think maybe instead of telling someone where to get the particular weirdass thing they've decided on, maybe I can come up with a better or more available solution. That's why I discussed the power.

To all who commented on the power, I see I forgot to say I am testing these amps here in the States, which is why I need to convert 208 to 230. To those who wanted to discuss the different aspects of power, and Y and Delta, I say ? ? I told you I had the voltage and wanted a pilot light, that's about all.

And what's available overseas? We're having custom transformers made, and the power there is 60 Hz.



However, this is an LED built into a night-light type bulb, with a candelabra tip on it, so it's meant to screw directly into 120 volts AC. I can't see how three volts of forward drop might be an issue if there's already something in there that handles the other 117 or so volts when this is powered from a regular socket!

You DID see the place where I said I'm getting this LED bub at Home Depot, not Mouser, right?


Electrically, simpler. I do, however, have to figure out how to mount three candelabra sockets inside a big gray electrical enclosure, positioned so they are easily visible. Three resistors are WAY easier than mounting and wiring three more candelabra sockets somewhere.

Ernie,

Perhaps you should reread your post, before reading my answer again. LOL I was trying to explain to you why the power factor should be good, and hence will not be an issue.


I think mounting the candelabra bases should be easy. Some of the bases in the link below mount into a round hole cut in a panel. Looks super simple to me... (This was the first link good came up with on a search of "candelabra socket")

[Link: grandbrass.com]

But you didnt say you couldnt have more than one!

No, I did not. I was asking about running A LIGHT off of 240 volts, which I sorta thought implied I wanted to put in just one. When buying them, I had already thought of using two in series, so was examining other approaches.

Ernie,

It seems like you want this to be easy...

So why didn't you just stop at an electrical supply house and buy an indicator lamp? It will probably be little more than the LED candelabra bulbs you bought, but will be made for panel mounting.

It also wouldn't have taken a week to figure it out!?