OT: Advice on making power supply

[347sixtyseven]

Guys, i need a bit of advice onmaking a power supply to run a few chargers for rechargeable torches at work.

The torches came from the US with 110v wall warts that power a charging dock thingy.

I want to run an Aussie 240v wallwart to power 4 or 5 of the charger units at the same time. The input requirements of the chargers are: 12v dc 500mA.

I want to make a regulated power supply to go between the wall wart and the chargers, it will have 4 or 5 output sockets to power the chargers.

Can anyone recommend what current output i will need from my wall wart to feed 500mA to each of 4 or 5 outputs?

Will there need to be regulation of the current?

I am assuming that current doesn't work the same as voltage when in parrallel. Therefore i will possibly need 500mA x 4 or 5 to provide the necessary total current needed.  Or will i? 

Any advice/recommendations greatly appreciated

Cheers

Gary

[R.G.]

Hi, Gary.

Yes, you'll need the number of chargers times 500ma to run the maximum setup. That gets you to 12Vdc, 2.5A, which is beginning to be a pretty big wall wart. Or you can use 12Vdc / 500ma for each one; 12Vdc 1A would power two, and so on.

There is another way. The total is only a bit over 30W. You could just wire up a box with a step-down transformer, even an autotransformer, in it and put USA-style outlets on the box, then use the original wall warts.

You'll have to wire the AC power box to do this. I normally don't suggest that people do AC power wiring for safety reasons. If you decide to try this path, do not do so unless you already know how to wire AC power circuits safely for yourself and anyone who'll use the thing after you leave. Or get skilled help to do so. There are many ways to die with AC power wiring, including dying in a fire years later, which is one that many people don't think about.

[347sixtyseven]

Thanks for the advice RG,

The fire risk is one thing i do think of as i earn my wages putting them out

Cheers

Gary

[brett]

 I bought a step-down transformer (240 to 110V, Arlec) for about $25 (if I recall correctly).  I use it quite often because most valve testers come from the US and run on 110 V.
cheers

[347sixtyseven]

Got hold of an old ibm laptop power supply last night. 16v and 3.36A.

Would it be possible to use this through a regulator of some sort to provide 5 outputs at 12v 500mA?

Cheers

Gary