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Topic: Hapless noob has one day to make an animated Christmas display on a van (Read 3900 times) previous topic - next topic


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!!


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:-

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.


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?
There are 10 types of people in the world, those who understand binary, and those that don't.


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).


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  :P )


I don't need the Arduino anymore.

What a shame!  I'd look for another reason!
There are 10 types of people in the world, those who understand binary, and those that don't.


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.


I don't think you need relays for that.

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

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)



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

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