wireing up a costume.

[Spider_senses]

I'm working on a production of Cats, and need to wire up a coat with lights. The designer is looking for # of bulbs not nesessarily wattage. It obviously has to be DC. Any hints or suggestions of type of bulbs to use to get the best bang for my buck without loading the coat with too many batteries.

The Technical Director has mentioned the use of mini christmas lights, but I don't know about the conversion to power it by DC

 

PS. I am across the pond so the christmas lights are 110v

[gareth]

Have you thought about LEDs? If you're looking for high output, low current draw and good battery life, they're the only way forward!

[Spider_senses]

yeah I have. It's just about all that soldering, resistor codes, and math. I was hoping for a simpler sollution.

 

but it is a good option if I wasn't so lazy :** laughs out loud **:

[Ike]

Right. Say you have a string of 20 christmass lights designed to run off 110V rms and these are connected in series there will be 5.5V rms (110/20=5.5) across each one. For them to be the same brightness as when you will run them off the mains you will need to put 5.5V DC across them. If you put slightly less across them they will be dimmer, if you put slightly more across them they will blow more easily. The brighter they are the hotter the filament and the hotter the filament the more easily it will break if they get banged. For this reason I would suggest running them a bit dimmer.

Having worked out the voltage you want across them next you have to think about the actual supply. If you can not get a battery for the desired voltage you will have to get a couple and connect them together. Connect one of the positive terminals to one of the negative terminals then make the other connections to the other two terminals.

As you will be using more than one lamp they should be wired in parallel, this also has the advantage that if one blows the others will remain lit. Usually the larger the battery in physical size the longer it will last. Using multiple batteries would mean you could hide them more easily.

Lastly there is the problem of heat. For safety I would suggest running them for a while before they get put into the costume so as to judge how hot they will get and fireproofing the coat may be advisable. Another advantage of running them a bit dimmer is that they will generate less heat.

[Spider_senses]

Thanks Ike

That's exactly the info I was looking for.

 

This forum rocks. :** laughs out loud **:

[Ellis]

Don't abandon the LED approachquite yet. Ike's suggestion means cutting up the string of lights and rewiring them in parallel. The current soon mounts up, and you will probably still be soldering it all together.

 

An LED has a voltage drop of about 1.4 volts. 5 in series is 7V or 14 in series is 14V. If you just use them in a series/paralllel network, you should not need to use any resistors.

 

LEDs have several advantages:

 

Lower power consumption

Less heat generated

Push the two pins through the fabric and make the connections behind - no visible wires.

 

If soldering is not your thing, try terminal blocks.

[Spider_senses]

It's a 5 min bit. The designer wants to have 50 lights on the costume. How many LED's can I use on one 9v battery to have it last that long. I understand the point of 14 in series is 14v. Does that mean I need a 14v battery to run them at full brightness?

The fewer batteries the better obviously.

 

Please help, time is of the essence. :** laughs out loud **:

[david.elsbury]

An LED has a voltage drop of about 1.4 volts.  5 in series is 7V or 14 in series is 14V.

Not quite... 5 LEDS is 7 volts, 10 LEDs are 14 volts.

:** laughs out loud **: -david-

[Spider_senses]

ok 10 LED are 14v. Does that mean a 14v battery?

[Ellis]

ok 10 LED are 14v. Does that mean a 14v battery?

Or there-about. You can get away with being slightly over or under - try it out on the bench first.

 

Ellis

 

P.S. Thanks lxdeptnz for correcting my typo.

[Mush]

LEDs are the best answer in battery applications. Some rough arthmetic:

 

1 LED takes typically 20 mA so

 

50 * 20 = 1000mA = 1A

 

 

PP3 9V battery in high quality alkaline is 500 mAh which means 500 mA for an hour or 1A for half an hour, in an ideal world, real life will be a bit lower.

 

So 50 LEDs for 5 minutes should be on face of it feasible, even allowing for power loss in resistors. In real world will work fine but use alkaline batteries and a fresh battery every performance.

 

Which colour of LED?

 

Red and similar colours have a forward voltage of ahout 2V,

White , blue and emerald green have a vF of about 3.5V.

 

This is an aproximation which will do for a lot of real world applications.

 

So lets say you wanted to use 50 Blue leds , LED needs 3.5V your battery is 9V, so wire 2 LEDs in series uses up 7V so need resistor to `use up ` excess 2V , don`t be temted to use a red LED in there, dosent quite work that way,now using calculator at:

 

http://linear1.org/ckts/led.php

 

tells you to use a 100 ohm resistor in line with your 2 LEDs, so you need to make up 25 strings of 2 LEDs and resitors in this format.

 

Mebbe easier to use 2 PP3 batteries in series to give 18V and less , 10 I think, longer series LED strings.

 

Some links

 

http://www.ledmuseum.org

 

http://www.ledshed.co.uk

 

http://www.superbrightleds.com

 

http://www.whitelightled.com

[chris512]

in will young's new video he wears a jacket with various small bulbs which looks quite funky, unfortanley have no idea how they did it!

 

ps. isn't wiring spelt with the 'e' B-) ** laughs out loud **

[Spider_senses]

Ok to review, and make sure I get it straight.

I am going to wire two 9v batteries together to get 18v.

I have 20mA super bright LEDs with a forward voltage of 3.5. 5 of the LEDs in series is a drop in voltage of 17.5. Leaving me with .5 over. .5v/.02A results in a 25ohms resister.(do they make resisters that small?)

I can then wire three more sets of (5LEDs in series) to the same set of batteries?

giving me a total of 20LEDs on two 9v batteries?

[Jivemaster]

For LEDs there is plenty of power in a PP3 9v battery. For reliability remember the coat will be cared for by technophobes, wire carefully to ensure that the wiring harness doesnt break, Lots of parallel circuits is better cos then if one fails the coat still works. Try using a 20mA constant current circuit to eliminate all the calcs and variables in series led ccts. get a variable voltage reg battery to IN, leds to common/adjust pin, Resistor from common/adjust pin to out pin. R= 1.5 / current in amps. Put several of these securely with a quality PP3 or AA holder

[Mush]

I am going to wire two 9v batteries together to get 18v.

 

That was my first though, would extend run time, 2 *500 mAh giving hour theoretical run time. Not really needing it use one PP3 9 V battery, and wire in parallel with individual resistor explanation follows

 

I have 20mA super bright LEDs with a forward voltage of 3.5

 

Cool as in cool white :-) , white LEDs are cool white if you want warm white use wheat -of -grain-lamps but battery pack would need to be bigger.

 

quote a bit of Jivemaster`s post as well...

 

Lots of parallel circuits is better cos then if one fails the coat still works.

 

Indeed, but in multiple series strings, failure of a string only loses 2 or 3 LEDs.

 

Try using a 20mA constant current circuit

 

Constant current is a great way to drive series strings as well, but not parallel strings of unresitored LEDs. one will act as current hog and run hot and get hungrier.

 

In this application need min 3.5V to light up a white LED AA/A cell 1.5 or 1.2 V recharegable , need 3 to work , adds weight. PP3 works fine.

 

Use resitor per LED parralleled bit of mindless soldering,or 3 way of smallest avail choc-bloc. Mount LED at 90 degrees from LED on some board and use velcro to attach assembly from interior of garment pointing out.

 

Can use very thin, or thick enough to make loom, but more strands means more flex for any given thickness, and wire to wire between boards.

 

Get resitors down to tiny fractions of an ohm and way into many megaohms.U.S suppliers would bepeople like add, www.com , Digikey Newark or BG Micro, or any of LED suppliers will do resistors.

 

We`ll be expecting photos :o