1
\$\begingroup\$

OK, let me 1st give you some background information.

I need to generate 40,000 lux of light in an indoor environment (in a area of around 5 feet by 3 feet) and I need the ability to turn the light on/off in 1 minute intervals for around 10 hours straight (about 600 off/on events in the span of 10 hours).

So far I've come up with two options. I can buy several high-watt compact fluorescent lamp (bulbs) and use a timer than can turn it off/on in 1 minute increments. I already have a timer than can do this so I have no problem with this point. However, I would need around 30-50 105 watt bulbs to generate this kind of light. The benefit of using CFL is that it can be turned on/off in a relatively short time (many are instant on but even if not it won't take more than 20-30 seconds). However, I'd need a ton of such bulbs.

My other option is to use a METAL HALIDE BULB. 1 such bulb can easily generate 40,000 lumens using only 400 watt (compared to 1500+ watt for the CFL bulbs). However, the main issue with these are that it takes anywhere between 3-5 minutes (sometimes more) for the bulb to reach full luminosity - and I need it to reach full luminosity within a minute or less (instant is ideal).

Furthermore (as Wesley Lee pointed out) I would need to wait several minutes to turn it back on after turning it off (I accidentally omitted this from my OP).

One solution I thought of was keeping the bulb on indefinitely and placing it in a box. The box will then open and close in 1 minute increments. Thereby allowing the light to illuminate the area for 1 minute and then when the box is closed no light will be emitted.

My question is how to make an apparatus that opens and closes in 1 minute increments? Or is there another simpler solution to my problem?

The solution needs to be automated (not manual).

Thanks

\$\endgroup\$
  • 1
    \$\begingroup\$ Not only it takes time to reach full luminosity but you cant turn it back on after you just turned it off. You have to wait a few mins. lrc.rpi.edu/programs/nlpip/lightinganswers/mwmhl/… \$\endgroup\$ – Wesley Lee Mar 8 '15 at 4:31
  • \$\begingroup\$ Maybe build something like this? Plus a servo? upload.wikimedia.org/wikipedia/commons/2/2b/… \$\endgroup\$ – Wesley Lee Mar 8 '15 at 4:32
  • \$\begingroup\$ @WesleyLee Thanks but a think this would cost tens of thousand of dollars to build. I'm looking for something that would cost a few hundred dollars max. \$\endgroup\$ – Michael Morl Mar 8 '15 at 4:39
  • \$\begingroup\$ I've built housings with diaphragms using the same mechanism, servo motors and plastic for no more than 30usd.. of course you need better materials cause of heat but the principle is the same, I dont think it would be that expensive.. but.. well.. \$\endgroup\$ – Wesley Lee Mar 8 '15 at 5:22
  • \$\begingroup\$ @WesleyLee Thanks.. Do you have names for the materials needed to build it? \$\endgroup\$ – Michael Morl Mar 8 '15 at 5:26
1
\$\begingroup\$

You could build a mechanical shutter operated by a servo motor and controlled by a microcontroller easily enough, but there is another issue.

Your 400W of input power is being turned into light and heat. I don't know what the efficiency of your proposed bulb is, but even if it was as high as 25% (dubious) you'd still need to dispose safely of 300W of heat continuously. When the shutter obstructs the light the waste heat will probably ramp up to almost the full 400W because most of the 40k lumens are going to be converted back into heat.

Have you looked for high power LED's (or LED arrays) that can generate the kind of light intensity you need? LED's can usually be switched on and off pretty much as required, and they're also generally more efficient than other light sources.

\$\endgroup\$
  • \$\begingroup\$ Any light source but LED light will work. LED lights cannot be used. Regarding the heat issue, I think we can get around that easily enough if the box is large enough. \$\endgroup\$ – Michael Morl Mar 8 '15 at 4:44
  • \$\begingroup\$ @MichaelMorl I suspect that you'll need fan-forced ventilation as well. 400W is quite a bit of heat. \$\endgroup\$ – markt Mar 8 '15 at 4:51
  • \$\begingroup\$ I guess this could be implemented once we get the box details. It should't be a problem to add a fan to a box that can open/close automatically. Thanks for suggestion though. \$\endgroup\$ – Michael Morl Mar 8 '15 at 4:52
0
\$\begingroup\$

This is too long for a comment, although it mostly does not address your question.

You need to do more research into your needs. A 400-watt metal-halide will never do what you want.

It's true that you can get such a bulb, and it will produce ~40,000 lumens. The problem is, this will not produce anywhere near the light levels you need. 1 lux is 1 lumen per square meter. 40,000 lux on a 3 x 5 area will need about 55,000 lumens. Worse, your bulb radiates over a full 360 degrees (technically, 2 pi steradians) and at one meter will provide a brightness of only about 6400 lux. And worse yet, if the bulb is 1 meter from the center of your 3 x 5 area, the corners will only receive about 4500 lux. (The light makes nearly a 45 degree angle, and the cosine of 45 degrees is .707).

In the absence of mirrors and lenses, I really doubt that you will get your 40,000 lux with less than 2 kW of electrical power.

\$\endgroup\$
  • \$\begingroup\$ I will use mirrors \$\endgroup\$ – Michael Morl Mar 8 '15 at 6:25
  • \$\begingroup\$ 3 feet by 5 feet is a pretty heroic set of mirrors. With off-the-shelf stuff you might get your electrical requirements down to 1 kW. Frankly, I doubt you'll do any better than that. \$\endgroup\$ – WhatRoughBeast Mar 8 '15 at 20:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.