Hey guys, I want to make my own LED strips for my latest moc. I want to have a separate battery box (non-lego) and a switch (non-lego). It is going to be a fairly easy project, but I need help with resistors. I don't even know if I need any. If someone could please help me, that would be great.

I have not bought anything so if you describe using something, I will probably just buy whatever you recommend.

Thanks!!

It will depend on the type of LEDs you're using and the power source. Here's an article on how to pick resistors for LEDs: http://www.evilmadscientist.com/2012/resistors-for-leds/

I have to go to radioshack to see which LEDs fit inside of a pin hole in a LEGO beam. That is how im going to pick the LEDs I use.

Thanks for the link to the article

You Will need SMD leds 0805

I am also trying but in my case I am searching for a thin wire. I bought some batteries Cr 2032 and the LEDs. I don't know how to get the wires yet but some SMD LEDs don't need resistors

Depending on what you want to do, there are already a number of ready-made products available with various power, light, and integration options. Here's one ready-to-go example (which could be easily re-wired for a different power source:

http://www.liteupblock.com/unlimitshop/index.php?cPath=36

ALL LEDS needs resistors to limit the current consumption. Yes, you can just slap a white LED on a CR2032 but it will not last forever and if you have more than one LED. chances are they'll emit different amounts of light

I'd not recommend SMD LEDs (0805 etc) unless you need exactly that small size. They're hard to to solder on, especially if you don't have much/any experience

3/5mm types are much easier to work with and 5mm fits in most LEGO holes/beams etc

That article about picking the right resistor is not good

You do not want - or need - to run the LED at the edge. You'll shorten the life heat could be a problem, not to mention power consumption

Most LEDs are 20mA types, they'll work perfect with 10mA (0,01A)

Basic formula : (LED Voltage - battery Voltage) / LED Current = R .... (3-9) / 0.01A = 600R .. 620R is standard and just fine

I allways use one resistor for each LED

Cheers,

Ole

Ok what should I do with this LED?

http://www.radioshack.com/5mm-red-led/2760041.html#prefn1=productType&prefv1=4-7+mm+lens&start=6&tab=tab1

To me it looks pretty expensive for an ordinary LED lamp that has have a pretty low brightness (10mcd) ! Note also that 5mm LED may not fit well a Technic hole (whose diameter is 4.8mm). Some LEDs have a slightly conical shape that make them better suited than pure cylindrical ones like this one (Radio-Shack should provide a mechanical drawing!)

That said... Here is how to calculate resistor:

- Maximum current is 28mA, let's use 25mA to be safe

- Nominal supply is 9V and typical LED voltage is 2.25V. Resistor will thus have to drop 9-2.25 = 6.75V

- Resistor is then 6.75 / 0.025 = 270 ohm. By chance this is a standard value...

- I also suggest that you use a protection diode (1N4148, 1N914, 1N4151...) across LED terminals. LEDs don't like to be powered in reverse!

(edit): I missed 1974 comments that describe solution quite well too!

Edited January 19, 201510 yr by Philo

Whoa, that is a lot of information. What is a diode going to do?? Do i need it. I just figured LED, resistor, switch, battery pack would be my set up. Do i need more??

Why not just use Lifelites? They fit through a Technic pin, they are prewired with resistors, and they are pretty cheap. I am using them for my new project and am pretty happy with them.

Yair, I've used Lifelites LEDs. I've also soldered my own LEDS, resistors and cables, then heatshrink-wrapped the bare metal parts and cable.

$2 per Lifelite LED isn't cheap, but comparing it to the work of soldering, heatshrinking and testing it's not actually too bad

Also solder and flux fumes are not good, nor are burnt fingers

Probably someone who solders all day every day could prep a batch of LEDs in minutes, but I solder once every 3 years

Considering using Lifelites for a project, mostly because they have flashing amber LEDs. Has anyone used their 9v adapter with a Lego PF battery box? Looks like it should work, maybe needs PF extension cable and a 9v system jumper plate?

Edited January 19, 201510 yr by andythenorth

Blakbird, thanks for the Lifelights link, didn't know the existed. When I wanted to add alot of led's to a project I went out and bought everything. Solder, Gun, heatshrink, LED's, Holder, blah, blah. That led to alot of coin and tons of frustration. My fingers are too damn big. Now I use most of what I bought for the homemade LED project, for re-wiring my jeep so all in all not bad.

I will be buying some lifelights. Any pictures of a project they've been used on here?

8275 Bulldozer fully-lit: https://www.flickr.c...157624355112320

This uses the now-discontinued PF brick from Lifelites. (With apologies to Rob @ Lifelites who is a very nice guy) the PF brick sounded better than the reality. You can use the IR remote to cycle through different lighting sequences (emergency vehicle, train, spaceship etc). Actually it's chore to cycle through the sequences, and not something that you need to do via a remote anyway - set it once, leave it set. Interesting experiment though.

https://www.flickr.c...rth/4732750063/

https://www.flickr.c...rth/4733394658/

Lifelites are a great product from a nice company.

Edited January 20, 201510 yr by andythenorth

I just want to build my own set-up. I am good with a solder gun and what not. but I needed to know what all I needed to buy

What country are you in? It would not be hard for me to find links if you're shopping at one of the large outfits (Farnell, Conrad, Digikey etc)

But it's really basic stuff, 500-1k resistors, 5mm white/red LEDs, some thin wire and heatshrink. Not rocket surgery

Im from the USA.

I know it is not rocket science, but i did not need to start a fire or something And well with my past... nevermind

So the resistor number does not really have to be an exact number, but greater than 500.

Also someone said i needed a diode, do i??

And just checking, but i need a resistor for each LED i use, correct?

Diode not needed, unless you want to continuously apply voltage the wrong way for eons of time

I would advice a resistor for each LED, yes

You can also get flashing LEDs btw, but hey have internal circutry and need 5-12V (depending on type)

I think I will just stick with the regular LED, but thanks for telling me.

I know seems like i dont know anything, but what gauge wire would you recommend

I'm building custom LED lighting too.

I need a little help. Should I add resistors anyway if my LED is rated at I_f = 30 mA, U_f = 3,3 V, but the actual current it uses is about 1,7 mA when connected directly to two AA accumulators in series (voltage 2,6 V)? Would resistor give some additional protection or is it unnecessary in this case?

Edited January 20, 201510 yr by sonar

I am not sure how to answer that question sorry, but when you finish can you post some pictures

Resistor give some additional protection IF you change your power supply.

2 AA = just 2.6V, you are using rechargeable batteries or you are using non-fresh or cheap alkaline batteries? With 2 AA good alkaline batteries you should get 3.0~3.2 Volt. Still less than those Uf=3.3V but pretty close. LEDs are cheap, you may try. But resistors are also very cheap :)

Resistor give some additional protection IF you change your power supply.

2 AA = just 2.6V, you are using rechargeable batteries or you are using non-fresh or cheap alkaline batteries? With 2 AA good alkaline batteries you should get 3.0~3.2 Volt. Still less than those Uf=3.3V but pretty close. LEDs are cheap, you may try. But resistors are also very cheap :)

I am using rechargeable batteries (accumulators?) that each supply about 1,2 - 1,3 V. That's why I get the odd 2,6 V voltage instead of 3 - 3,2 V if I used alkaline batteries.

Now that I think of it I will use LEDs without any resistors since the current is 30 times lower than maximum allowed. Which is even better because the whole assembly without resistor is smaller, easier to make and can fit every tiny corner on a Lego model.

Edited January 21, 201510 yr by sonar

So I knowwhatiam going to do now, thanks to all of your help. Thank you

But now I have ne last question, series or parallel circuit?