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Discussion Boards => General Discussion => Topic started by: usher42 on January 27, 2008, 01:49:42 PM



Title: Christmas Mini Lites for buildings
Post by: usher42 on January 27, 2008, 01:49:42 PM
I like using xmas clear mimi lites for my buildings Is that a good idea . But i can only find xmas mini lites only at xmas times, is there anyplaceelse i can find them/


Title: Re: Christmas Mini Lites for buildings
Post by: Jim Banner on January 27, 2008, 05:47:37 PM
Mini Christmas lights are excellent for buildings if you run them off a transformer! 

Mini lights often come in strings of 50 bulbs wired in series.  The ones that come in strings of 100 or 200 are usually 2 or 4 strings of 50.  With 50 lights in series and running on 125 volts, each bulb receives 2.5 volts.  Finding a 2.5 volt transformer to run them off is next to impossible.  But a string of 5 of these bulbs in series requires 5 x 2.5 = 12.5 volts which is ideal to run off a 12 volt transformer.  Each string draws about .2 amps of current.  So a 12 volt, 1 amp transformer could operate 1 / .2 = 5 strings for a total or 25 bulbs.

These bulbs tend to be relatively short lived.  Experience suggests somewhere around 200 hours at their rated voltage.  But here is the good news -  If you operated them below their rated voltage, their life increases and it increases a lot.  Suppose you run a string of 6 in series across 12 volts.  Each bulb will now receive 2.0 volts  (12 / 6 = 2.0).  And they will last over 18 times as long.  They will also be somewhat dimmer, but still quite bright.    That is a pretty small penalty for getting a 3600 hour life.  If you added yet another bulb in each string, the life would increase to a whopping 27,000 hours.  The lights would be dimmer still but probably still usefull.

So why the insistence on running the mini lights off a transformer?  In a word, SAFETY.  Model railroads tend to have a lot of wiring under them.  Track feeds, throttle buses, switch motors, building lights, animation, maybe even some signal lights.   And over time, the wiring tends to get changed.   A few small buildings moved out to allow a new industry here, a change of track plan needing a new turnout there, and maybe an animated crossing gate complete with flashing lights and bell somewhere in between.  One moment's inattention, one snip of the wrong wire, and it could be the last wire you ever snip - if you have 120 volts floating around under your layout.  Using strings of mini lights plugged into a wall outlet may seem like a bright idea, but if you insist on trying it, I hope and pray that you never ever learn in a blinding flash why it is not.

 


Title: Re: Christmas Mini Lites for buildings
Post by: ebtbob on January 28, 2008, 10:23:55 AM
Usher,

     Model Power is now offering mini-lights with replaceable bulbs in a base with peer and stick adhesive.   They are rated at 12-16 volts.  They come packaged in a set of 4(I have that package in front of me) and then,  maybe,  8 and/or 12.   You can go to their website at www.modelpower.com to get more info.
       Also,  I agree with Jim about using a transformer,  other than the one used to run the trains,  to power the lights.   By connecting them to the DC track screws and using the speed control,  you can vary the brightness of the bulbs.