Replacing batteries with power supply

[clearchris]

Hi.

I am looking at replacing 4 C cells with a wall wart, because I'm tired of going to the store for C batteries. There's a wrinkle here, the unit pulls ground and voltage off 4 batteries in series, and also two in series. So, 4 batteries, three wires.

(GND)--[- +]---[- +]-(3v tap here)-[- +]---[- +]-- (VCC 6v)

I figure I can replace it with a 6v wall wart and a dc-dc buck step down converter for the 3v circuit.

Is there anything I should be concerned with here? I think it might be a good idea to put a 12v MOV in there to protect against spikes, I imagine that batteries don't have that particular problem, so there would be no protections against it on the board.

It drives a board, an actuator and an LED display. I assume the LED is running at 3v, the rest at 6v.

Thanks!

[Agent24]

Re: Replacing batteries with power supply

You might want to use a linear regulator for the 3v rail, a DC-DC converter may be too noisy, if the unit expects batteries.

For the same reason, you might want a linear transformer for your wall-wart too.

Or maybe I'm just being paranoid... lol

[stj]

Re: Replacing batteries with power supply

you need to work out how much current you need on each voltage first.
and how exactly is this 3v used?
keeping in mind the 3v supply may be referenced to the + rather than the ground.

it could even be running +/-3v centertapped.

can you foto or draw the circuit?