Step 3: What do you need? Parts and Tools

Picture of What do you need?  Parts and Tools
The parts you need to add an AC adapter are fairly simple, but harder to find than I expected. I ended up going to Radio Shack -- they carry specific-voltage adapters, individual tips, and panel-mount sockets to match the tips. At most places you have to by a "universal" adapter, and can't get the sockets at all.

For the TinyLove mobile, which uses 3 AA batteries, I bought

4.5V adapter (700 mA) 273-1765
Size "M" (2.1mm ID, 5.5mm OD) plug 273-1716
Size "M" panel-mount socket with switch 274-1582

For your application, choose an adapter with an output voltage that matches the type and number of battery your device uses.

You will also need lengths of thin (24 gauge or smaller) wire, one with black insulation and one with red. I cannibalized mine from some left-over four-conductor signal cable. Start with 6" lengths and trim them back when doing the soldering (Step 5). A wire stripper will be quite handy, but someone with some skill (not me) could use some small wire-cutters or scissors.

You'll need some tools: The TinyLove mobile is held together with weird triangular-bit screws. I found the bits at McMaster-Carr Industrial Supply (items 5941A11 through 5941A14).

A 21/64" bit will make the exact hole needed for the panel-mount socket. You could also use a 1/8" Dremel bit, followed by the Dremel ball grinder to enlarge the hole.

A soldering iron, solder and flux are needed to connect the wires. A solder-sucker might be helpful, too, when disconnecting the leads from the battery terminals.
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dbucher12 years ago
So if I were to convert a Hot Wheels Criss Cross Crash set that uses 4 D batteries, what adapter and parts should I buy?
Id like to know this as well!
cliffypop2 years ago
Many thanks for the helpful reply! The batteries are in series as they're connected in a daisy-chain. Also, the housing has "12v" printed in large characters. I tried to find any info about calculating wattage from volts and Ah without success. I found an equation for watts=volts*amps, but that's not the same ampere-hours.
kelseymh (author)  cliffypop2 years ago
Right. You can't calculate watts from volts and coulombs (== ampere*second). Watts are units of power, which is energy used per unit time (watt = joule/s). (And, since W = V*A, you have V*A = J/s, or J = V*A*s = volts * Ah/3600). To convert energy to power you need to know how fast you're discharging the batteries.

When you used the 1A and 2A wall warts, did they get hot when you were trying to use the vacuum? If so, the vacuum was trying to draw more current than those adapters were rated, and you'll need a higher amperage adapter.
cliffypop2 years ago
I have a (no-longer-very) rechargeable vacuum I'd love to convert to a wall wart but have been failing with various adapters I've tried. The vacuum uses ten 1.2v (1300mAh) batteries. So that equals 12v total. I thought a 12v adapter at 1.5Ah would do it, but the unit ran very low and kind of pulsed off and on every second or so in a very about-to-die way. I tried a 12v, 2Ah adapter with similar results. The batteries run in series so I know I need 12v. Do I have to multiply the mAh rating by the number of batteries too? That would be 13Ah but that doesn't make sense since mAh represents capacity and not amount of power which is voltage. Any help is much appreciated!
kelseymh (author)  cliffypop2 years ago
You need to know whether the vacuum was set up with the batteries wired in series (which would be 12V), all in parallel (which would be just 1.2V), or some combination of parallel and series. If you've already opened up the unit, then you "should" (depending on how it was built) be able to see the outside of the battery holder and trace how the terminals are wired together.

Also, mAh represents the total charge stored (ampere = coulomb/second). If you multiply by voltage you get total energy (joule = ampere*volt). That doesn't provide any information on the way the batteries are wired, just their total output.
redtux7773 years ago
I have 4 AA batteries in series in golden tee golf game I have. The batteries last 3 to 4 hours.
I am trying to do the math on that. Does that mean I would need 6v .5A power cord?
viv_virus064 years ago
i'm planning to run my remote controlled helicopter on ac adapter. i know that it use 9.0V but i don't know what mA should i buy. can you help me?
kelseymh (author)  viv_virus064 years ago
Do you mean you want to run the control box from an adapter? You obviously can't connect the helicopter itself to an AC adapter; it won't be able to fly :-) Did you read the manual? Usually toward the back there's a specifications sheet that should tell you the voltage and current usage.
i'm connecting the ac adapter to the remote, or the controls. it requires 6 1.5 volts batteries. the box only specify the voltage requirement and the mAh. i cant find the mA requirement. can i use any 9v adapter without taking note of the current usage requirement?
kelseymh (author)  viv_virus064 years ago
Hmmm....yeah, that's not enough information to solve the problem. In principle, you could measure the current draw with a multimeter and four-lead bridge, but it's not important. Choose an adapter with a high current rating. The remote will only draw as much current as it needs; as long as the adapter can supply at least that much current, it's fine.
thank you very much! you helped me a lot.
anyway, how can i set the polarity of the adapter to its correct setting?
jayhawk675 years ago
i have a fountain that requires 2 double a batteries what adpater should i use?
kelseymh (author)  jayhawk675 years ago
Each battery is 1.5V.  If they're connected in series, you'd need a 3V adapter.  If they're connected in parallel (unusual), you'd need a 1.5V adapter.
ty very much