Powering LEDs in a structure

[IowaFarmBoy]

I don't normally light structures but I scratchbuilt a background structure that has an enclosed loading dock with inner and outer doors. One outer door is open and I have LEDs to light the area so that it isn't just a black hole. Additionally I have blinking LEDs to simulate the lights on loading dock clamps which will draw attention to the area hence the need to light the dock.

I am thinking of using 2 batteries temporarily. What value of current limiting resistor is needed for 4 LEDs in parallel?

What's a good choice for permanent powering of these LEDs and perhaps others, a wall wart with the right resistor?

 

[julienjj]

getting a cheap 12v wall adaptor might work well !

 

[ianacole]

What value of current limiting resistor is needed for 4 LEDs in parallel?

It will depend on the power values of the LEDs. Check this thread where I worked through some of the calculations: http://www.modelrailroadforums.com/forum/showthread.php?t=17760

Plenty of folks on here can help you if you have additional questions.

 

[LFDRR]

If the LED has a forward voltage of 1.5-1.8 volts you could power it using one 1.5V battery without a resistor.

 

[Larry]

You can buy a plug-in adjustable transformer at WM that goes from 1.5 volts to 12 volts.
All of my LED's have a 560ohm resistor for 12 volts. That's what I put in all my engines.
My lites that I ordered from China for bldg. lites all have 560 ohm resistors for 12volts.

 

[RW&C]

Most LEDs I've found operate well at about three volts. Two AAs could power several LEDs in parallel, if you didn't want to get into wall warts and resistors. I have an old hand-held fan, with the motor removed and two wire leads sticking out the front, that I use to test LEDs and LED applications. It hasn't fried anything yet.

 

[IowaFarmBoy]

These answers were a lot of help. I was also searching the internet and found this page. http://www.quickar.com/noqbestledcalc.htm

 

[ianacole]

These answers were a lot of help. I was also searching the internet and found this page. http://www.quickar.com/noqbestledcalc.htm

Pretty slick!

 

[Larry]

These answers were a lot of help. I was also searching the internet and found this page. http://www.quickar.com/noqbestledcalc.htm

Larry, do you have a lot of LED's that you are going to use, if not, send me a PM w/your address & I'll send you as many as you want w/some resistors & how to brochures.

 

[IowaFarmBoy]

Here's the structure and it needs dock lights.

For a power supply I found this link. http://reckerclub.tripod.com/id105.html I have several AT computer power supplies available to use. There are other sites that show how to convert newer ATX power supplies. These power supplies are well regulated and even small ones will supply more power for LEDs or low voltage lights than many home layouts can use. The LEDs I have are rated @10 ma. A 200 watt computer power supply would provide somewhere around 40 amps using the 5 volt output and 16 amps using the 12 volt tap. That means that the number of LEDs you could power is 4000 @ 5 volts or 1667 @ 12 volts. Even if you have loss due to wire size and distance that's a lot of LEDs lighting up! And it would work to power other things of course.

I am not an electronic expert so if I calculated this wrong feel free to correct me.

I PM'd you, Larry.