Cheap and dirty project for stage props. Help!

I need help building a quick and dirty solution for lit stage props. I am involved with a local dance company that specializes in Philippine dance. One of the dances is called "Pandanggo Sa Ilaw" or "The Dance of Lights." ... How cool is that for a flashlight head like me??

The dance involves lit drinking glasses which are wrapped in a light silk scarf. Traditionally the glasses are lit with candles but due to fire safety codes, candles have been banned for all our performances.


For several years now I've made a cheap solution for the company. All I did was use old incandescent Christmas lights. 2 bulbs spliced in series to a 9v battery. It was durable enoegh and survived a few falls of the dancer dropped and broke the glass. It was nice because they could simply find any store selling 9v batteries near their performance for a quick solution.


Over the years I've exhausted the spare Incan bulbs and they have slowly lost the lights. They've tried using those cheap coin cell tea lights but 1) they aren't bright enough for stage performance use, and 2) coin cells are harder to find and too small to replace in the field.


The incandescent lights were sufficiently bright for the first 10 minutes or so, which is fine because the dance only lasts 4-5 minutes. But of someone forgot to unplug the battery then we would waste another 9v battery.


Warm LED Christmas bulbs are all I can find now. While I would LOVE to develop a bare LED, Rechargeable solution for them, this project has to be done in literally 1 week for their dress rehearsals.


For now I would like to buy one string of warm white LED Christmas lights. Target sells the Philips brand for 11.99 and has 60 LEDs with spares. I was planning on doing the same hack and slash method and combining 2 LEDs in series to a battery.


Will a 9v battery blow the LEDs? I can source a resistor of needed and splice in line if I have to. I don't have the time or expertise to do research at the moment so I'm going with what I know so far.


Ultimately it would be cool to get a RCR123 to drive an LED for a few minutes . Even cooler of can flicker. It doesn't have to be bright, just something to match 2 Incan Christmas bulbs which was equivelant to a real candle or 2. Then at each performance they can throw them on a charger.


The professional tea lights that restaurants use (Norex Safelight) are pretty bright and rechargeable, and could be a solution but they cost 30 a piece... I don't think they'll spend that kind of money.


Btw there will be about 30 units made which is why I'm trying to find a quick and dirty solution for now.


I'll try to post pictures if i have the tine so it'll make some sense.


Your help is much appreciated!

LEDagent said:

Warm LED Christmas bulbs are all I can find now. While I would LOVE to develop a bare LED, Rechargeable solution for them, this project has to be done in literally 1 week for their dress rehearsals.

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Fast, reliable, and cheap. Can do, if you've got a few hours to solder and test.

For now I would like to buy one string of warm white LED Christmas lights. Target sells the Philips brand for 11.99 and has 60 LEDs with spares. I was planning on doing the same hack and slash method and combining 2 LEDs in series to a battery.


Will a 9v battery blow the LEDs? I can source a resistor of needed and splice in line if I have to. I don't have the time or expertise to do research at the moment so I'm going with what I know so far.

Click to expand...

Flickering is tough. Try series-wired 2 or 3 LEDs with a resistor. An estimate for forward voltage is 3.2v, and you'll want a nice low current, 20 to 40 mA. A 9V is quite capable of supplying this for several hours of gradual dimming. Check wedding 'table favors' for ready-made flickery candles in Wal Mart or Target while you're snagging Christmas lights.

You want LEDs with an 'inverted cone optic' for maximum all-round visibility. This puts a cylindrical chunk of plastic atop the LED die, with a cone cut out of the top. This creates a bright 'spot' inside that cone that is very visible (Unless the LED is pointing directly towards or away from you, it's visible). These LEDs can be quite bright, but should have the heatsinking you can manage with their stubby little legs.

For a FAST (Tape and go) solution, tape a warm-white LED onto a CR2032 cell. This will be quite bright and probably not burn out, and can be made in about 1 minute.

http://www.youtube.com/watch?v=MCu7qZt3OBM&feature=youtube_gdata_player

Here is an official video of our company. At 15-25 seconds you can see a short snip of a rehearsal of the dance. You can see the size of the glasses and the scarfs they use. The brighter the lights the better it would translate on stage, but the Incan bulbs were pretty good.


BTW at 12 seconds you can see me and my wife dancing for 1 second

AnAppleSnail said:

Fast, reliable, and cheap. Can do, if you've got a few hours to solder and test.

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Soldering I can do quickly, it's the testing I don't have the time and resources for. The quick and dirty version of this would a crimp here and a crimp there, a resistor, 9v battery connector, and the battery.

AnAppleSnail said:

Try series-wired 2 or 3 LEDs with a resistor. An estimate for forward voltage is 3.2v, and you'll want a nice low current, 20 to 40 mA. A 9V is quite capable of supplying this for several hours of gradual dimming.

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This sounds excellent. 3 bulbs would suffice for brightness. What resistor values do I look for? I'll run down to the local electronics store this week.

AnAppleSnail said:

You want LEDs with an 'inverted cone optic' for maximum all-round visibility.

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The LED Christmas lights I'm looking at have frosted globes, so that should help with this project. When I get a chance for a more refined product I'll definately look into this optic. Thanks! I would have bought a batch of the wrong type.

AnAppleSnail said:

For a FAST (Tape and go) solution, tape a warm-white LED onto a CR2032 cell. This will be quite bright and probably not burn out, and can be made in about 1 minute.

Click to expand...

Most of these squeeze lights I've seen use 2 CR2032... Isn't that 6v direct drive? This sounds like the solution I will go with if I can't get my schedule together this week. The 9v solution worked nicely because I can put Velcro on the bottom and it would hold nicely with all the movement.

Like AnAppleSnail said, 2 warm white emitters in series connected to a resistor powered by the 9v battery could work well. A 100-200 ohm resistor should work. Maybe hook the LEDs up to a potentiometer and adjust the pot till you get the desired output, then measure the resistance of the pot and find the closes cheap resistor to that resistance. All this, and probably a switch too, could fit on a 9v battery connector, just wire everything in series.

If you want flickering would be harder to do and could be a project for next year. Maybe you can find a way to modify the tea lights to work with brighter LEDs. Use 2 - 3 AAA batteries (maybe in a cheap 3 AAA battery holder) for longer runtimes.

LEDagent said:

This sounds excellent. 3 bulbs would suffice for brightness. What resistor values do I look for? I'll run down to the local electronics store this week.

Most of these squeeze lights I've seen use 2 CR2032... Isn't that 6v direct drive? This sounds like the solution I will go with if I can't get my schedule together this week. The 9v solution worked nicely because I can put Velcro on the bottom and it would hold nicely with all the movement.

Click to expand...

Voltage for a simple LED circuit:

We use loop law (Vbatt = Vload1 + Vload2...) and Ohm's Law (V=IR).

First, assume Vbatt is 9v and use 2 LEDs. For small current draws on a 9v battery we can assume this reasonably. Next, Vled is about 3.2v per LED. We need Vled + Vresistor to be equal to 9v. 2*3.2 = 6.4, and 9-6.4 = 2.6v. At 20 mA, we'll need 2.6=(0.02A) * R, or 130 ohms.

For 3 LEDs, we see that 9v = Vled + Vres would be impossible: 9v = (3*3.2) -Vres, or in other words Vres = negative 0.6v! Put 3 LEDs on the 9v cell and they will light up...but perhaps not at full brightness. As the cell drains, its voltage will drop and output will drop quickly. 2 LEDs may be much brighter than 3.

Using coin cells: Coin cells have capacities about like 150 mAh with high internal resistance. This means that they don't have much energy, and their voltage drops as they deliver current. 2 CR2032s is 6v open circuit, but drops lower when driving most LEDs. White, blue, and green LEDs run fine on 2 CR2032s.

The short version: Use 1 or 2 CR2032s, and tape any number of warm-whites on. See if 2 kills a single LED, or see what your runtime is with multiples. Use a 9v and 100-150 ohms with 2 LEDs, or try with 3 and no resistor. Absolutely compare this to your existing lights, or test under the stage lights. Good luck!

For flickering you could use red blinky led (used in candles to simulate fire) wired in series with other two warm white leds and 9v battery and most probably no resistor.

Thank you everyone for your input. I finally was able to rush over to my local electronics parts store to grab the cheapest components I could find for a trial run.

I burned through 2 sets just before I found what went where. For a quick and dirty project, I was quite surprised with how bright these turned. I'll eventually add pictures when things settle down a bit.

Here's all the parts needed

9V battery
9V battery connector with leads
crimp connectors
warm white LED Christmas lights (50 LEDS)
1/2 watt resistor.