Where can I get a 12 volt to 3 volt power adapter?

Question

I want to use a electronic 3 volt device from a 12 volt car battery so it will run much longer. I am going to install a air bubbler in my boat (the portable type with a few feet of hose and a air stone on the end to be placed in any minnow bucket and keep them alive). They sell a 12 volt aerator for $40 but I am trying to go with the cheaper $10 style so I can just pitch it when it no longer works and replace it without taking a $40 loss each time. Where do I buy one?

Answer 1

I not promise this will work, but, if it done correct, it should. May need to buy a very small motorcycle battery for this and just recharge it. May use a 6 volt if they have them and only two resistors.
First shop around for that pump. I bought one at Wal-Wort less than $10 and it use the D-Cell Flashlight battery. Which I see you found, but, I bought the big Yellow one and it works after a year!
As mentioned you may try radio shack. IF, you want you can make something cheap. I not know how to explain all the technicals but here the basic idea.
When you place a resistor on a battery(One side to + and one side to -) you can measure voltage across the resistor and it show 12 volts. Now place four resistors in series, this when they in a row end to end and the two open ends to +/- on the battery. I would use power resistors that are ceramic, looks like it made from stone. When you measure across one you get 3 volts, two give 6 volts, three give 9 volts and all four give 12 volts. They are cheap if they free. They all need to be the same size, so, look at the color bands and be sure the colors are all in the same order. You may need some big resistors. Radio Shack also sell them and you sure to have the correct and same size. If, the person know what they doing (which I doubt) they may be able to help you figure this out.

Read here;
http://www.tpub.com/neets/book1/chapter3/1-12.htm

In the first picture the two resistors are the same size and it have a 20 volt battery. Measure across one resistor and you get 10 volts, measure across both and you get 20 volts.

Answer 2

Try Radio Shack

Answer 3

Radio shack may be you best bet. I have never heard of an adaptor that will do a 12v DC to 3v DC conversion.I would just use two 1.5v D cells in tandem,but that's what you want to get away from,right?

Answer 4

radio shack