What LEDs and batteries to buy, and where?

January 25, 2012 8:15 AM

I'm doing a craft project and would like to install two red LEDs that are powered by a battery pack with an on/off switch. I would love your opinion-advice on what to buy and where to buy it.

- Handiness level: good to very good. Specialized tool ownership: novice. I have used soldering irons and been competent with them, but I've not had one for years and have had no need for it since. I'd really rather not buy one just to complete this project, so anything I can assemble with twisted wire and black electrical tape is a winner.

- LEDs: red. Their size doesn't really matter - in my mind I'm thinking of the LEDs the size of the ones used in throwies but really, whatever works best.

- I would prefer LEDs be diffused with more of an omnidirectional output as opposed to clear. It will be almost impossible to mount them so that they're pointing to the exact same place and I'm worried about the viewer seeing them as one brighter than the other based on their viewing position. Strength over distance is not as important as visual consistency.

- I need two feet of wire between the battery pack with on/off switch and the LEDs themselves.

- These will need to stay lit for at least 4-5 hours. I don't know if I can just use a few CR batteries or if I'm going to need a 4-AA box, or what. The instructable on throwies says they'll last a week off of a CR2032. I'm thinking I'd prefer a little black box for some AAs with an on/off switch built in, just so there's less for me to tape and assemble. Ease of battery replacement is important. I don't want to have to fight tape to stick in another CR or use a screwdriver to open a plastic box to put in another 9v.

- Durability: short-term. Doesn't have to last for years, only days.

- Buying all of this in one place would be great. If you think my local RadioShack has everything I need, then awesome. I'd love recommendations for particular part numbers to seek out so that I can call them and ask in advance of arrival. If RS is out, then where would you go to buy such things? I have a little time, so buying online is fine.

posted by komara to sports, hobbies, & recreation (12 answers total)

If your local RadioShack doesn't have what you need, the two main go-to shops online for this sort of thing are Mouser and Digi-Key, though their websites can be somewhat daunting unless you know precisely what it is you're looking for.

Here is a simple LED circuit that includes the use of a resistor, so you might want to add that to your parts list.
posted by jquinby at 8:23 AM on January 25

this is the type of thing Radio Shack is very good with. I'd suggest going in to one of the retail locations and asking for help.
posted by txmon at 8:24 AM on January 25

You could accomplish the diffusion with a ping-pong ball. I don't see why you need anything more elaborate than LEDs attached to watch batteries.
posted by odinsdream at 8:34 AM on January 25

Seconding the use of a resistor, else it will only light very briefly.
Calculations in jquinby's link.
posted by MtDewd at 8:41 AM on January 25

I can't speak for ratshack's ability to help.

You'll need to figure out the voltage for the two LEDs, if you want them serial or parallel. I think you'll need 3 AA batteries. Then use a resistor calculator (eg this one or google your own) to figure out your resistor, and have at it.

LEDs come in a variety of sizes, voltages, angles of view/lenses. I like mouser electronics, but find what meets your needs (size, leads for wiring, lens, color, etc)
posted by k5.user at 8:41 AM on January 25

I don't see why you need anything more elaborate than LEDs attached to watch batteries.

Because the LEDs themselves are going to be mounted to something semi-transparent, so I don't want the entire battery mount sitting behind it and visible, not to mention that area will be harder to access than the back of the project, so running wire away from the LEDs is what I'd prefer to do.
posted by komara at 9:01 AM on January 25

Looking around Radio Shack's site (in part to see what's available in-store here) I found this which is almost exactly what I want, already in one single package - except it blinks. Dangit.

But that. That's what I'm looking to make, if I can't find one to buy.
posted by komara at 9:16 AM on January 25

You know what? I may just buy something like this and tape over all the others so that they're not exposed.

Still glad to listen to recommendations, though, and I'll stop thread-sitting now.
posted by komara at 9:28 AM on January 25

for $5 bucks, that pre-made is cheaper than anything you'd wire together yourself..
posted by k5.user at 9:40 AM on January 25

I've been using LEDs for halloween lighting projects so here are a couple of things to know:
-Ebay. You can get literally hundreds of LEDs for a few bucks. I ordered 50 packs for a buck each and paid a couple of bucks shipping. These came with matched resistors too.
-You gotta use resistors
-Polarity. LEDs are not like lightbulbs - they have a polarity
-Wall warts are great for static projects. You can run a lot of LEDs off of one with appropriately voltage, and you can buy them a local thrift shops for super cheap.
-wire: Use the thinnest cheapest stuff you can find. This usually turns into the most expensive part of my projects.
posted by Big_B at 12:43 PM on January 25

I'm gonna go ahead and take k5.user's answer as best. Product ordered, done thinking about it. Thanks for all the advice!

If I'd known that such a product existed and was so cheap I probably wouldn't have bothered asking - but now I know even better what will be required for a similar project in the future.
posted by komara at 1:15 PM on January 25

Follow-up: I bought the thing I linked to, it arrived, I installed it (and taped out the other lights) and it works exactly like I wanted it to. Thanks for all your help and for letting me know I wouldn't find anything better and cheaper in the DIY realm.
posted by komara at 1:30 PM on February 14