LED strips in buildings

[woodbine]

I have some leftover snippets of 12v LED strip. If I snip it up into elements and pop them into buildings, wired in parallel from a bus and powered by an AC/DC 12v 1.25 amp converter walwart, are there any things to watch out for? Such as maximum/minimum number of units? What might blow the LEDs, burn the house down etc. I think I'm OK, but want to be sure.

I don't mind simple yes (with reason)/no.

Edited March 22 by woodbine
spelling!

[ISW]

6 hours ago, woodbine said:

I have some leftover snippets of 12v LED strip. If I snip it up into elements and pop them into buildings, wired in parallel from a bus and powered by an AC/DC 12v 1.25 amp converter walwart, are there any things to watch out for?

I've got plenty of 'lengths' of 12v LED underneath my baseboards to light up the Lower Level, all wired in parallel off a single 12v bus wire. I too am considering installing same inside some scratch built buildings (cereal packet ...), but will watch out for:

1. The double-sided tape on the back of said LEDs is not to be trusted. It has a nasty habit of peeling way, particularly where the wires join due to the weight / stiffness of the wires. Use the smallest wires you can get away with, say 7/0.2 wire.
2. The LEDs do tend to get fairly warm, so it's probably a good idea to 'tame them down' with a suitable resistor (see also below)
3. The LEDs are probably too bright for the interior of a building so, as above, it's probably a good idea to 'tame them down' with a suitable resistor
4. LEDs do fail now and then (although I've not had any fail under my baseboards), so it's a good idea to make them 'accessible' after the building is assembled. All my building have removeable roofs to provide such access (and allow me to retrofit the LEDs later).

As an alternative to a resistor in 3) & 4) you could use an LED dimmer (which I've already bought a few of), something like this:

 

In TheBay use the search term "Mini DC Motor Speed Control Driver Board 3V-35V 5A PWM Controller / LED dimmer".

 

Ian

[DCB]

I  am struggling with the idea of a  small chunk of a 12 volt LED strip working.    Most LEDs like about 2.2 volts ish So I would expect them to be wired in blocks of 5 or 6 in series to work on 12 volts or need multiples around 2.2 / 2.7 volts depending on how many you have in circuit.   I would test the chunks with variable voltage supply, I use my  Morley controller and a voltmeter starting at about 1 volt off load to see what voltage the start to glow at.
I have a load of LEDs in buildings off a couple of 3 volt buses,  many are oranges and yellows  but in my colour light signals the  reds need much bigger resistors than the greens , but on 3 volts the resistors run cool.
You will struggle to set the house on fire with LEDs but the resistors are a different matter, I have several scorched card buildings where someone else has used LEDS on 12 volts and put the resistors in the building.
The good way  to start a fire is to use rechargeable batteries and short them out  in the vicinity of cardboard., I haven't managed it myself but I melted a Lima class 37 body when  2 X AA batteries shorted.
 

[SRman]

2 hours ago, DCB said:

I  am struggling with the idea of a  small chunk of a 12 volt LED strip working.    Most LEDs like about 2.2 volts ish So I would expect them to be wired in blocks of 5 or 6 in series to work on 12 volts or need multiples around 2.2 / 2.7 volts depending on how many you have in circuit.   I would test the chunks with variable voltage supply, I use my  Morley controller and a voltmeter starting at about 1 volt off load to see what voltage the start to glow at.
I have a load of LEDs in buildings off a couple of 3 volt buses,  many are oranges and yellows  but in my colour light signals the  reds need much bigger resistors than the greens , but on 3 volts the resistors run cool.
You will struggle to set the house on fire with LEDs but the resistors are a different matter, I have several scorched card buildings where someone else has used LEDS on 12 volts and put the resistors in the building.
The good way  to start a fire is to use rechargeable batteries and short them out  in the vicinity of cardboard., I haven't managed it myself but I melted a Lima class 37 body when  2 X AA batteries shorted.
 

 

All of the strips I have encountered and used have sets of three LEDs with resistors, with cutting marks between each set of three and solder tags at each potential cutting point.

[ColinK]

I have led’s in buildings (and coaches), wired in parallel and powered by batteries.

[GrumpyPenguin]

Just buy the single LED's ready mounted on a small board 12v rated from one of the adverisers on here, run them at 8/10v smooth DC & you won't have any issues.

 

They are not expensive.