Powering a few surface mount LEDs via battery?

[Lacathedrale]

I've got one of those big self-adhesive strips of LEDs that I was using to light up a layout - they're lovely and bright, and very low profile. these are the specific Amazon item: https://www.amazon.co.uk/gp/product/B00WQFP3AO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

I'd like to use half a dozen to light up a little diorama - but would rather not have a power connector, so my thoughts were a pushbutton with a timer on the front, and a battery box underneath. The whole diorama needs to fit into roughly 24cm x 12cm x 20cm including the frame so space is fairly tight!

 

Thanks so much,

[Tricky Dicky]

You should be OK as long as you cut them off the tape in multiples of three where indicated. If you are using them as overall illumination then as indicated you will need a 12V battery. If using them to illuminate the insides of buildings you might want to consider using a smaller voltage battery to give a more realistic light. How long your battery will last will depend on individual cell size.

 

Richard

[Dave John]

Oddly, here is a timer, er, just on time....... 

 

 

It will however use a bit of power ever with the lights off, so might need a battery switch as well. The leds would probably run ok if you just replace the relay with them, bigger leds might need a bigger output transistor. 

[Lacathedrale]

4 hours ago, Tricky Dicky said:

You should be OK as long as you cut them off the tape in multiples of three where indicated. If you are using them as overall illumination then as indicated you will need a 12V battery. If using them to illuminate the insides of buildings you might want to consider using a smaller voltage battery to give a more realistic light. How long your battery will last will depend on individual cell size.

 

Richard

 

Three of them should be more than enough for lighting the diorama - only about 6" x 4" x 4" - but I wanted to have a separately lit signalbox interior, as @Dave John has spoken about - I gather that I can run that off the same 12v supply, but maybe with a separate switch, and a resistor to limit the current? I don't really know how that works!

[Tricky Dicky]

14 hours ago, Lacathedrale said:

 

Three of them should be more than enough for lighting the diorama - only about 6" x 4" x 4" - but I wanted to have a separately lit signalbox interior, as @Dave John has spoken about - I gather that I can run that off the same 12v supply, but maybe with a separate switch, and a resistor to limit the current? I don't really know how that works!

The short answer is yes. Each 3 LED strip already has a resistor which is why you only require a suitable power source @12V adding further resistance in series for the strip going in the signal box will have the effect of dimming the light emitted. What you cannot do is use less than 3 LEDs per strip.

 

Richard

[Lacathedrale]

Gotcha, so if I want a single LED (for the signalbox interior) then I should use as standalone LED with resistor, yes?

[Brian]

Hi

They are listed as being "Waterproof" this means the LED strip has a clear tubular like covering. This makes cutting them and then soldering feed wires to the two pads harder.  IMO its best of layout use to obtain the standard (non waterproof) LED strip!  They are also white you may prefer a more yellowish tint for buildings?  Then look for Warm white strips  Often around 3000K

Edited May 11, 2019 by Brian

[Tricky Dicky]

17 hours ago, Lacathedrale said:

Gotcha, so if I want a single LED (for the signalbox interior) then I should use as standalone LED with resistor, yes?

 

Yes. If you intend to use the same power supply @12V then start with a 1K resistor although I think you will have to double the value to get a realistic light effect.

 

Richard

[DCB]

Not a great idea to use a 12 volt battery, these are usually rechargable and pack a big punch Amps wise if shorted. Easily enough to melt your signalbox or set a card building on fire. , Use a 1/2 amp fuse if you must use rechargables. 

Watch the voltage from a model railway power unit, 12 volt nominal is often 20 volts plus for 12 volts.   12 volt  Computer power supplies usually are 12 volt so if the strip is intended for a genuine 12 volt then 20 volts wont do much for the life of LEDs

I use an LED strip from Poundland to give moonlight in the rabbit hutch over the outside branch terminus. It has many LEDs and works off 2 X AA batteries in its built in battery box and has a nice on off switch. Not bad for a quid.