how much power do projectors use?

[mixedgas]

Solar powered laser shows have been done at Burning Man.

Steve

[Galvonaut]

What about the diffuse reflections off the solar panels at night? No no, using them as beam stops will not work.... ;o)

Get the angles right and you can harvest the reflections too! Maybe make some sort of infinity mirror type solar array, then you could power the whole gig with it and maybe even feed in to the grid

Steve: People under-estimate what is actually possible with solar. There are quite a few solar stages on the festival scene near me who seem to run quite effectively with careful calculations.

[The_Doctor]

Well, don't get me wrong, but you're suggesting a complex solution to what might be a simple problem.

When people are expected to go out of their way to help you, it's up to you to declare useful context up front! Ask a silly question, get a silly answer. You with-held context until the latest post, only then using it to try to prove a point. You got it ass-backward. You should have declared that info up front, instead of blaming me (or anyone else) for not knowing what you would not reveal. If Buffo gave you an answer you liked better, you either got lucky, or you told him things you didn't tell anyone else.

In most other contexts where lack of mains power combined with some kind of travel were the defining context, a small vehicle and a sinewave inverter and a mains cable would be the simplest answer. Almost any other answer would cost more, and require a bit of engineering.

EDIT:
As you're not exactly fond of setting out the problem for detailed analysis in advance, you're left with the guidance that several people have given you: Try it. Rehearse it like an artist on a stage. If you can't set scope for predictable engineering, then this is your only shot. After all, you don't want nasty surprises out there than you can do nothing about, right? And if you can get the same test conditions of temperature and humidity, do that too.

More edit. It's a very beautiful place. How will the show be set in that scale? If you can get good pics of the event, I think they might be the most interesting laser pics I'll have seen.

[The_Doctor]

Ok. It does mean you'll have to cover for all possibles with no top up or recharge though. One thing I said was that it may be better to just take extra charged batteries if possible, run in parallel. That way you prevent voltage drop, and also reduce risk of killing a battery by deep discharge.

This really is a 'proof of the pudding' situation though, you have to eat it to know if it's any good. Temperature and humidity (and wind speed too) can make a big difference to thermal dissipation, and therefore efficiency. It's a really tough engineering task trying to predict and calculate any of that, so try to simulate worst case, test it, see how much the battery voltage drops at twice your intended session length (expect to retry, etc, out there, stuff happens, you'll likely need to do it for whatever reason). So long as whatever you do, the total battery voltage does not fall below 11 volts, you should be ok. (But if it falls below 11V, get it charged ASAP after, unless you're willing to risk sacrificing the battery. Ultimately you might even get a bit of extended emergency time out of it, but that WILL sacrifice it, so try to gauge time to below 11V from a resting start volts of around 12.7V after a full charge) In the end it boils down to how much battery you can carry.

Edit:
If you can't get deep cycle batteries, uprate that low-volt threshold to 11.5 volts. (You may decide to use standby batteries for extra capacity and less weight per rated Ah).

[The_Doctor]

There's a site called the 'Battery University'. It's awesome, but it's a big read at times. Have a go though, it might be easier to grasp than you think because they don't say much that isn't useful.
In (very) brief.. 'Leisure' batteries are really cheap, designed to run fridges on day trips in boats and such. 'Marine' batteries might be confusing because that term might mean anything from day trip in a boat, to something like a big sealed type used on oil rigs (because they have a low risk for fire and explosion compared to other types).

Your best bet might be to get a cheap job lot of same type, sealed. Make sure they are sealed type, because you need to be safe. Also, they will work upside down! So any orientation is ok. This is where 'parallel' comes in. Basically, connect all the positive terminals together, and all the negatives. If you can get a few cheap inline car fuseholders and 10A fuses, do it, that way you will prevent a possibility of dangerous vapourisation of copper, and some very nasty burns. Trust me, you do not want that to happen out there.. A few tiny cheap fuseholders might save your life. Ideally use one for each battery. The idea is to use your UPS in such a way that you wire it to a bank of small batteries sitting nearby.

Edit:
Linkage:
http://batteryuniversity.com/learn/a...ased_batteries

More edit:
If you Google for the Enersys 'Powersafe' batteries you'll find very good basic manuals on charging and lifetimes for high quality sealed deep cycle batteries. A high quality UPS might use a small version of those. Alternatively, a cheaper one will likely use a standby battery like those made by Yuasa. These are the cheapest, which is why getting a few at a discount, then wiring parallel, might be your best shot.

[goldenstarwinni]

hehe tks friend .

Hehe, don't worry Winni - I get the 'wrong end of the stick' a lot and I'm a native English speaker!

[steve-o]

Just get one of these and be done with it .. (my .02)

[The_Doctor]

Just get one of these and be done with it .. (my .02)

Given how small that is, I second the motion. May be important to check the quality of its output though, linear PSU's can pass high voltage spikes from generators that kill electronics. I was going to perform a solo bit of synth wizardry on an SCI Pro-One at a gig in a derelict building, and the synth died before I could even test it was set up right. Very bitter occasion.. It might be worth getting a heavy duty mains filter just to be safe and take the risk out of this. A residual current breaker also, if it hasn't already got one.

The energy density of a flask of fuel plus the weight of that generator would beat haulign lead-acid batteries and risking high current shorts in remote locations with no easy reach of medical help.

[buffo]

It's only slightly larger than a car battery, and it's very quiet.

Adam

[steve-o]

Yes Honda generators have a reputation for being very quiet.