Rule of Tim: Making a cheap Genny safe for a Puter.

Lee_D came up with the following;:

Run the electrics through a UPS ... Uninterruptible Power Supply, which is in effect a big battery, which also has the effect of smoothing the power flow and providing a 'clean' supply.

Maplins do one at about £30 ish that should work well enough.

I run our computer at shows straight off a cheapo generator - no problems.

Richard

I'd expect a decent laptop PSU to isolate variations in the input and create a decent DC output. The projector may be a different kettle of fish. As suggested elsewhere, use a cheap UPS, or possibly a surge-protector 4-way adaptor as an even cheaper, less good option. Check the draw of the projector and that it is within the limits of the generator and the UPS, especially when first powered up.

Cheers , I'll check the current drawn first, seems maplins do a UPS at £29.00 so once I'm sure I may commit then.

How does one work out the initial start up loading of the Projector, is there a formular or is it another gadet?

Lee D

Trouble is, there's two very different types of UPS.

One connects mains direct to output until it fails, when it switches on the inverter and draws from the battery.

The other has no AC connection between input and output. The inverter runs full-time, and the mains-to-DC is trickle-charging the battery.

The second type is a really good noise filter -- the battery acts as a huge smoothing capacitor on the DC supply to the inverter.

But switched-mode PSUs rectify to DC as the first stage, and then run the transformers at mugh higher frequencies. so they're pretty noise- tolerant. I reckon it's the projector you have to be wary of.

If it's notable then the book ought to tell you. I don't know much about it, but the lamp is an expensive consumable. It will draw different current when flat cold until it gets hot, with a corresponding effect on supply voltage.

Projector lamps also need to be allowed to cool down properly (yes, that was an expensive show...)

In order to answer the question of power startup, yes, lots actually, but newer projectors will softstart. Never, ever run a video projector off a dirty generator, ever.

To measure what it uses, get a plug in power and energy monitor;

Best way to help you reduce your energy consumption.

I'd be very wary of the ordinary small and cheap non-AVR or non-invertor (smart throttle) type gennys. At the =A380 price point the =

OP is looking at the small 600 to 800W cheap and only vaguely regulated jobbies. Alright for a light bulb or small telly but may well struggle to start a fridge or freezer...

I'd expect a modern projector to be using a low voltage bulb not one directly connected to the mains. These high power low voltage bulbs are expensive (three figures before the decimal point) and rather finickity about their supply. I'd expect the PSU to provide enough isloation from the supply but how well that PSU would reposnd to a genny bouncing up and down from 150 to 300v is another matter...

Putting a UPS in circuit only *might* even out supply variations it depends on the design and function of the UPS. I suspect the =A330 Maplins jobbie will just pass the input to the output with perhaps a bit of filtering when the input it present and produce something quickly when the mains input fails. My APC SmartUPS basically does that but can boost or reduce the "passed through" power as well without fireing up the invertor section. Judging by the clunks it makes in switching I suspect that is acheived by changing tappings on an (auto?) transformer.

But can be wildly inaccurate on devices with switched mode PSUs. A useful tool but you need to know it's limitations.

What were the circumstances of his log off? I've corresponded with Brian in the past, normally about ISDN, iPABXs and OS/2.

Yeah, and having blown one or two in the past, I felt it worthwhile pointing this out to Lee!

It's handy to see what's being drawn from the socket, and scary to see how much (as an excample) our coffee maker costs us in the office!

I only learnt from Pedt in unnc, but the original posting in demon.service was:

"I regret to announce that he died suddently from Acute Myeloid Leukemia, which he was only recently diagnosed with, although he had been ill for a while."

Shame. Brian had a lot of 'clue'.

SG: Strictly speaking there are three types of UPS, but who's counting? Between the two you describe below (off-line and on-line respectively) there is a half-way house, typically, called in-line.

At the cheap end of the market you can only get off-line units which only switch on if the power fails completely or if there are major sags/surges in the ac power. They are totally unsuitable for use with a generator if you're expecting the UPS to do some smoothing ... cuz it won't. For that you need at least an in-line unit at mucho more dosh :-( and even then it won't compensate for frequency variations, which are very common with small generators.

You can get some good info from >

Lee, before buying an el-cheapo UPS take a look at

Agreed, never physically met but was always helpful and knowledgable on the net.

Mucho appreciated, I aborted any clever stuff until I'm suitably confident that I'm not going to put something in to orbit.

:0)

Lee D