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My boss just told me that by close of business Thursday (12-06-12) I have to decorate the company van with animated lights. When I asked what my budget was she told me "We'll see". I chose to be optimistic and interpret this to mean $20, despite historical evidence indicating it means $0.

By the way, I don't really know what I am doing. I am coming here in need of help!

I did some poking around and found a rechargable lead-acid 12V, 0.28A/H battery. I don't even know if its charged or how to recharge it (though presumably I can find someone at my job who does). I have an Arduino Uno, some wires, a half breadboard, and precious little else. Currently I am powering the Uno via USB, and will probably just have a laptop to power it.

I read that the small Christmas lights are 2.5V. Correct me if I am wrong, but if I connect 5 of the lights in a series that should work with the 12V battery. If I attach many of these sets of 5 in parallel then I am only limited by how much charge the battery has. I can hopefully get away with putting 6 in a set and make some sort of snowflake design.

I see that 12V relays are $10 a piece at Radio Shack, and I obviously do not have time to wait for shipping from a cheaper place. There may be some alternative places in town. If I wanted to be able to animate 6 different groups of lights independently does that mean I would need to use 6 relays?

Assuming that I magically had 6 relays, I could attach them in parallel to my battery, then have each relay control several sets of 5(6?) lights (where each set is in parallel). Is that correct?



How best do I solve this problem? I appreciate all the (much needed) help!!

[Reply #1 on:]

The bit on your diagram that says relay should actually be the relay contacts. The relay coil would be connected to a transistor and then to your arduino. Like the first diagram here:-
http://www.thebox.myzen.co.uk/Workshop/Motors_1.html

I read that the small Christmas lights are 2.5V.

No it depends on what type of lights they are. I am assuming you mean filament lights not LEDs

However, if it were me I would go to a thrift shop and get a cheap string of LED lights that could be operated off 12V.

[Reply #2 on:]

Can you "overlap" them and just use 3 columns of LEDs and 3 relays?  Just enable the ones you need to make the I, II, and III symbols.

Sorry. I just read that you're trying to make a snowflake pattern... You'll need all of them.  What kind of animation are you liking for?

[Reply #3 on:]

Don't you just love bosses that give you complex projects with no budget?

If it is a van, why not use the 12v from the power panel/cigarette lighter?  It would save you from having to buy a 12v battery.  If you are going to use commercial A/C lights, you could use a voltage inverter on the power panel, but unless you already have one, it will blow your (non-existant) budget.

I would think going with cheaper light strings that have their own batteries (using coin cells) would be the way to go, and if you want to add programming, put a relay between the lights and the battery.  Locally, I've seen such strings at the Paper Store and Hallmark stores (check drug stores as well).

[Reply #4 on:]

Oh, the glories of working for a not-for-profit.

Just talked with my boss and she told me that "oh its animated now?", despite having asked for animation. Agh! Thankfully without animation this becomes a lot simpler: namely, I don't need the Arduino anymore.

I already have the 12V battery. Our maintenance guy is going to charge it overnight for me. I did not think about using the cigarette lighter, and I am not sure how to safely utilize it without going out and buying something. Plus, I already have the battery.

I am about to go out hunting for 12V light strings, etc at Hobby Lobby, Walgreens, and where-ever else I have time for. Hopefully I will be able to make this work (electrically) and hand the actual decorating off to someone else.

Thought I do not need to use relays for the project as is, would my circuit above have worked? It is my understanding that the Arduino pin out activates a transistor that completes the circuit to the relay, I just did not draw that part of the diagram. (or even bother to use the correct symbols  )

[Reply #5 on:]

I don't need the Arduino anymore.

What a shame!  I'd look for another reason!

[Reply #6 on:]

That's the spirit!

I don't know how it would be useful in this project without an investment no one is willing to make. I've been wanting to make a delta robot, but since I have no money either, that has been postponed indefinitely. I have a couple of servos laying around, some LEDs, a transducer someone randomly gave me, and lots of LEGO NXT parts. I'm open to suggestions!

PS: To make things more hilarious, I just learned I am doing this because the van will be in a parade, and there is an award given for the best decorated vehicle.

[Reply #7 on:]

I don't think you need relays for that.

Ordinary transistors will be much cheaper/easier/less risky.

[Reply #8 on:]

Well it is Friday now.  How did it go?

[Reply #9 on:]

now its saturday, how about an update? curious minds want to know more!