Er... Is this thing going to explode and maim me?

Dubious Drewski · Jan 5, 2009

So I need portable power because I'd like to start using my lights on location. Today I bought the Motomaster Eliminator Powerbox 800 and I'm trying it out just now.

I charged it and I tested my lamp and my heater - both work perfectly. Then I plugged in one of my Opus Studio lights. It works. It powers on and functions, but it audibly buzzes. This box's outlets are 120v AC, and that's what these lights require, so what's going on?

Is this dangerous? Am I going to fry these lights?

tsaraleksi · Jan 5, 2009

I used a terrifying 30 year old power pack for a while, it hummed and the lights in the house dimmed when I plugged it in. I used it for a couple of months without any apparent ill effect. I will not speak to the chances that it will wreck your lights-- I imagine it shouldn't but I am NOT an expert.

Dubious Drewski · Jan 5, 2009

Well on the back of the lights, it says they require 120V AC at 60hz. But on the powerbox, it doesn't specify at what frequency it's oscillating. Can I assume that it's a mismatched frequency that's causing this? That's probably it, but I wonder how much wear this is incurring on the circuitry in the lights.

I think this is a question for the folks over at the EDABoards.

Dubious Drewski · Jan 5, 2009

Ok, I found out that it is indeed outputting at 60Hz, BUT it's not at 120 Volts. It's 115. Would that make that much of a difference?

davebmck · Jan 5, 2009

No. 120V is a nominal value. Most AC power is 115 to 110V.

stsinner · Jan 5, 2009

Drew,

Standard household AC, at least here in America, is 110-115. It's just called 120 a lot, but most usually called 110. Since we get a great deal of electricity from you, it is probably pretty close to the same.

It's very possible that what's going on here is due to the battery circuitry going through a step-up transformer and simulating 60 hertz. One of the most inefficient types of transformers.

When you use a battery to produce AC, it's not true AC, but switched DC from positive to negative at 60 hertz, usually with powerful transistors. It could be that the AC produced isn't clean, and therefore isn't perfect-you'd have to see it on an oscilloscope to be sure. Most likely it's a square wave or a clipped sine wave, but is a little different than a sine wave created by the true AC created by a generator. What you've got is "fake" AC, so you may see some unusual activity with it. That being said, if it were me, I wouldn't plug sensitive electronics into it like a laptop. Lights and stuff like that should be fine, but I don't think it's really quality AC coming out of that. Maybe that explains the buzzing, but maybe not.

Dubious Drewski · Jan 5, 2009

Hmm, thank you for that insight. I never considered the shape of the oscillation and perfect sine versus square waves. Would you consider a strobe to be "sensitive electronics"? On the box, there's a photo of a girl using her laptop off of this thing. And she has a really big smile, like she's really enjoying herself and her computer isn't buzzing ferociously and/or exploding.

Hmmm.

GeneralBenson · Jan 5, 2009

Maybe she was being electrocuted by her laptop and couldn 't let go, or stop smiling; which is what she was doing when the electrocution started, because her friend just farted.

jlykins · Jan 6, 2009

GeneralBenson said:
Maybe she was being electrocuted by her laptop and couldn 't let go, or stop smiling; which is what she was doing when the electrocution started, because her friend just farted.

That just made me LOL. That's funny.

JerryPH · Jan 6, 2009

Fart jokes... the best... lol

At our last strobist meeting, some poor bloke had the winds. Eventually a lady strobist who was shooting with him finally had enough. She walks away and comes back an hour or so later. She comes right beside me and without so much as an introduction, a look at me or hello, starts talking calmly:

"man, I don't know that guy over there, <points to the gaseous man>, but I bet his pics all come out like sh!t, becuase thats all that I smell anytime I hear his shutter go off!"

The way she so calmly said it without a trace of humor made me laughed so hard I had tears in my eyes.

She looks at me and says:
"Tears, huh... uhh, yeah, I had those too. Maybe we need to step a little further away from that direction"

She had to have had a British background, becuase her expression and sense of humor were so dry it was hilarious.

stsinner · Jan 6, 2009

Dubious Drewski said:
Hmm, thank you for that insight. I never considered the shape of the oscillation and perfect sine versus square waves. Would you consider a strobe to be "sensitive electronics"? On the box, there's a photo of a girl using her laptop off of this thing. And she has a really big smile, like she's really enjoying herself and her computer isn't buzzing ferociously and/or exploding.

Hmmm.

I know that my Dell laptop has a huge power supply in the cord that filters the incoming AC as it rectifies it to DC and steps it down, so maybe it's okay.. But one time I ran my TV off of my portable power supply during an outage, and the picture was kinda shrinking/growing with some rhythm.. Can't imagine that was good for it. And, no, I wouldn't consider a strobe to be sensitive electronics.

Big Mike · Jan 6, 2009

From the little bit that I've read about portable power, you will want nice 'clean' power for your strobes. I don't know if they are considered 'sensitive'...but I have heard that dirty power will significantly reduce the life of your bulbs and maybe the units themselves. A good power source will have a pure sine wave converter to give you nice clean power.

A Vagabond system isn't really all that expensive, that's what I would have recommended.

Dubious Drewski · Jan 6, 2009

Aww man. This Vagabond has a "Pure sine wave inverter" built in. That's so awesome. /sarcasm

Hehe. So THAT's what I need to look for, eh? Well It sucks I already paid $200 for this powerbox (which is the best I can buy in my area) and it's not as adequate as this other thing, which is $300 and would probably also be very heavy and expensive to ship to me.

Hmph!

What to do...