how do I shorton a Mini Light set without blowing all the mini bulbs when i

[Old Sarge]

Technical problem.. I am working on making talking face.. I have the head outline and lights done and they work fine..

The problem is when I try to light up one section of the mouth ( using 18) mini lights about one minute after turning them on all the blubs Blow..

 

Is there a minimum number of mini lights that have to be connected for them to not blow or maybe I have a crossed wire causing them all to blow?? I am trying to get a 4 section mouth working, top lip, center lip, bottom lip and a O vowel. I am confused as to why the top lip section 18 lights are the only ones blowing so far.

 

Thanks in advance

 

retired_old_sarge@yahoo.com

[godman]

So did you already shorten the sting? Check out this video below

 

 

http://www.holidaycoro.com/kb_results.asp?ID=35

[Denny]

If you are physically removing 18 bulbs from a string, you are probably blowing the bulbs.  Mini lights are wired in series with each one reducing the amount of voltage going to the others.  If you divide the voltage, 120/110 volts by the number of lights in the original string, you will get an approximation of the maximum voltage for each bulb.  For example, 120 volts divided by 50 bulbs in a string gives you something like 2.4 volts per bulb.  Now, if you reduce that same string size to 18 bulbs, you are putting approximately 6.7 volts through a bulb which is designed to handle only 2.4 volts. 

[Max-Paul]

Kirchoff's Law, look it up. Basicly it says that the voltage applied must be dropped across all elements of the circuit. So for example if you have 35 lights in a circuit, the each light must drop or be rated for about 3.4 volt lamps. At the same time if you have 20 lamps, each lamp will need to drop 6 volts each. And if you are cutting down a 50 lamp string which is about 2.4 volts each. So applying 6 volts across a lamp rated for 3.4 or worse 2.4 volts will pop them every time. Take the extra lamps and put them in something that will block their light. But it must not hold water. If you want to make things and those things are electrical. Best learn Kirchoff's law, Ohm's law, and Watt's law. Otherwise your going to burn things out and or start a fire. At this time it appears you have no such knowledge and I highly suggest you stop modifying electrical devices before you get hurt.

[Steven]

Mini bulbs are most often 2.5v (50 bulbs per string), but are also available in 3.5v (35 bulbs), 6v (20 bulbs), and 12v (10 bulbs). Your best but would to buy a 20-bulb string and cover 2 of the bulbs with black caps or tape.

[Steven]

Mini bulbs are most often 2.5v (50 bulbs per string), but are also available in 3.5v (35 bulbs), 6v (20 bulbs), and 12v (10 bulbs). Your best but would to buy a 20-bulb string and cover 2 of the bulbs with black caps or tape.

[chandalen]

As mentioned above, your better off getting a shorter strand or covering the lights you dont need.

 

But the real answer is approx a 11 ohm resister for each light removed (on a 50 light strand). So if you remove 10 lights, you could use 1, 110 ohm resister in their place.  I'd say round up because resisters have a 1%-15% tolerance based on their striping.

 

If you want to go this route...  get a 1-1000k  110v potentiometer from radio shack.  Crank that bad boy all the way open and slowly decrease it until the lights come on.  If you lower it too much you'll blow the lights.  The even better way would be to measure the voltage across an empty bulb, and use the pot to get that voltage when the lights are removed.  ALWAYS start with too much resistance than too little.

 

I stole these calculations because I was too lazy to do them myself!

 

25w/120v = .2083a
125v/.2038a = 576.09ohms
576.09ohms/50bulbs = 11.52ohms/bulb
11.52ohms*20bulbs = 230.4ohms

[Steven]

25w/120v = .2083a

125v/.2038a = 576.09ohms

576.09ohms/50bulbs = 11.52ohms/bulb

11.52ohms*20bulbs = 230.4ohms

 

Don't forget:

.2083a^2*11.52ohms = 0.500watts

.2083a^2*230.4ohms = 9.80watts

 

This means your 11Ω resistor will dissipate a half-watt, so you better get a 1W resistor.

 

Another option, since you're using a LOR controller, is to make sure your sequence keeps the lights dimmed. To find out what dim level to use will require experimentation.

[caseofbeer]

I did a talking head with minis, with cut down strands of 50.

Then named each channel with the percentage that I couldn't go over.

Every bulb equals 2%, so a 14 bulb strand would get no more then 28% fade up.

I also put in the channel name the 1/4 dim, 1/2 dim, and 3/4 dim fade values for different effects.

7,14,21,28. For the 14 bulb example.

Then program VERY carefully! It's a pain, I can't recommend it. Also hard to share anything you do with it. I'm going to LEDs, but would use resistors if I did minis again. (Minis twinkle so nice)

If cutting down a strand other than 50, remember to refigure the percent rate per bulb.

[Daryl]

If these lights are incandescents, wouldn't it be easier to go buy the black out caps for the bulbs you don't want to see? I heard the caps don't work on LEDs although I thought I saw somewhere quite a while ago that someone had black outs for LED's.