Replacing Batteries with DC Power Supplies: What to Consider

[ZPlayer]

Hi, Everyone!

Is it possible to replace regular AA (or other) batteries with external DC power supplies (in general) or are there fundamental differences between these two sources of power? For example, my X-Box 360 joysticks (controllers) require two AA batteries each. I have Nokia power adaptor (old), 5V and 890mA. With appropriate voltage divider, I should be able to connect power-carrying wires to the joystick, so it will get 3V. I understand that it will practically immobilize my joystick and make its wireless connection useless, but I did not choose wireless joystick anyway. Also, I know about power kits for X-Box 360, but they include a rechargeable battery, so that solution is applicable for X-Box 360 alone, and does not answer the general question.

What happens in case if the joystick (or whatever the load is) draws more current than 890mA? Also, should I be concerned about the waveform of the voltage from Nokia adapter (DC source) and its compatibility with other battery-driven appliances?

Thanks to all who reply.

 

[berkeman]

You can replace batteries with an equivalent DC power source. It's best to measure the current consumption first with the batteries, to be sure that you've sized the DC source correctly. I doubt that the joyostick draws anywhere near 890mA. You could also estimate the current consumption by how long the batteries last, and checking the AmpHour rating of the batteries.

Be sure to get the polarity right...

 

[rolerbe]

Battery voltage tails off as the batteries drain, so I would expect the controller to be tolerant of any voltage variations due to ripple on the DC supply. I don't know the specs, but am quite sure the controller will not draw anything near 800mA. Better than a voltage divider would be to use a voltage regulator to get down to 3V. Look for a 78M33. That and two cap's and you're good to go.