Push Light Lite Brite?

December 27, 2006 6:13 PM

How can I wire a bunch of push lights together and run them off of regular power?

My plan is to take 100 push lights and somehow attach them to a board (or something similar) in a grid shape, so that people can turn them on and off and make patterns, kind of like a big Lite Brite.
They usually run on batteries, but this means I have to get my hands on 400 AAs, which isn't cheap, and from what I've read they tend to drain batteries pretty fast.
Is there any way to do this without electrocuting myself? I don't have much experience with electrical projects, but my brother does and I can get him to help me if there's like, soldering involved.

posted by exceptinsects to sports, hobbies, & recreation (11 comments total)

You can get 120v A/C push lights.

A friend of mine is using the battery powered lights for a photography project. We spent some time last week sourcing lights online and at places like Home Depot. We found far more A/C lights than battery powered lights.
posted by b1tr0t at 6:25 PM on December 27, 2006

Just to be clear, this is what I mean by a push light.

and unfortunately I already have 100 battery-operated lights, so getting the AC ones is less optimal.

It is a good idea--but how do you plug them all in?
posted by exceptinsects at 6:33 PM on December 27, 2006

Your link doesn't give specific power requirements but we can infer them by using the 8 hour battery life. A double-A battery has from 1100 to 2700 mAh of energy, depending on standard or alkaline types. So each light needs, say 200 mA. For 100 lights you need 20A. Thats a pretty big supply. Your cheapest route would be to get an old PC power supply for about $20. Then you can just wire all of the lights in parallel. No, you can't electrocute yourself with 5 volts.
posted by JackFlash at 6:51 PM on December 27, 2006

Get a step-down transformer that will convert 120 Volts AC to 6 volts DC (assuming each lamp takes 4 AAs), then wire the lamps off the DC side of the transformer. Wire them in parallel (get your brother to show you what that means, and teach you to solder).

If they're LED lamps (like the one you linked to), they draw very little power (lets say 70mA), so a 1.5 Amp (1500mA) model like the DCTX-615 on this page should power 10-20 of them, easily.

If they're incandescents (like flashlight bulbs), then they draw quite a bit more power, and you'll need to use additional transformers. Look for an amperage rating on the bulb. If it draws 200mA (milliamps), then five of them would draw 1000mA (1 amp) -- so put 5-6 on your 1.5 Amp transformer (leaving a little headroom). It's not uncommon to see bulbs that draw 500-750mA in flashlights/lanterns, so look at your bulb before blindly wiring 5 or six together because of something you read on the internet.

Another option would be to get a larger 6V Lead Acid battery, wire all of them to that single battery, and then put the battery on a slow charger. You'll get the buffer effect of the battery, which will keep you from overloading your transformer by turning on too many lamps, and you won't need dozens of transformers.
posted by toxic at 6:56 PM on December 27, 2006

The page you linked says they run on 4 AAAs and expect 4.5-6.5 volts, so it sounds like the batteries are probably wired up in the usual series configuration: there are two wires (positive and negative) going to the battery compartment, and inside the compartment the batteries are wired up end-to-end.

You could connect the negative connections from each light together to one wire, and the positive connections to another, and connect that pair of wires to ... something that can supply 5-6 volts at quite a lot of current.

How much current? The best way to find out is to measure the actual current (easy with a multimeter, which your brother presumably has). As a rough guess, divide the lifespan the website mentions (8 hours) into the capacity of a typical AA cell (2850 milliamp-hours) to get about 350 milliamps per push-light. A hundred of them would then draw 35 amps --- that's really a lot of current. A reasonably beefy desktop computer power supply would be able to handle it, though you sometimes need to jump through some hoops to get them to work outside a computer.

Alternately, you could wire up smaller groups of lights to individual power supplies that can supply less current. You could even wire them up to batteries, say 4 'D' cells to a group instead of 4 'A' cells per individual push-light.

This seems like a very doable project for someone new to electronics, esp. if you can get the occasional help from your brother. Soldering is not difficult, btw, once you've had someone show you what a good joint looks like vs. a bad joint.

[On preview: what they said.]
posted by hattifattener at 7:05 PM on December 27, 2006

Where did you get 100 pushlights? This sounds like a fun project (well, except all the soldering).
posted by phrontist at 8:12 PM on December 27, 2006

Get a step-down transformer that will convert 120 Volts AC to 6 volts DC...

A stepdown transformer yields AC. Something that produces DC is called a "power supply" and there's more to it than a transformer.

I think the idea of finding a scrap PC power supply is a good one. Coming up with one that can pump 20 amps shouldn't be too difficult.
posted by Steven C. Den Beste at 8:41 PM on December 27, 2006

And if you can't, you can wire power supplies together in parrallel.
posted by phrontist at 10:02 PM on December 27, 2006

I'm not sure that putting supplies in parallel is actually a very good idea, since their output voltages probably won't match exactly. It would be better simply to put separate circuits on each. Since the load is lots of small items, there's plenty of flexibility to create combined loads which match the specs of separate supplies.

It doesn't seem to me as if paralleling supplies actually would buy you anything for this particular application.
posted by Steven C. Den Beste at 11:04 PM on December 27, 2006

I got the lights on eBay--it was about $30 for 100!

Unfortunately, it doesn't say anywhere on it what the volts are--the page I linked to was not exactly the same as the ones I bought.

Here is the auction--however when I got them they were not in the box shown.
posted by exceptinsects at 9:38 AM on December 28, 2006

Well, a single AA cell is anywhere from 1.2 to 1.5 volts depending on the chemistry it's using, so if they use their batteries in series (which they almost certainly do) then my last post should still be valid. You'll want to actually measure the current draw, though it's probably in the same ballpark.
posted by hattifattener at 10:27 AM on December 28, 2006