Maker Pro
Maker Pro

Easy question about AC adaptor/battery



Jan 1, 1970
As the rectifier is inside you don't have to care about the pins at
the plug. (And don't have to open it to search for the regulator which
is not present in all speakers). A 12V (13.8V) accumulator should work
fine. Capacity should be 1Ah per operating hour (worst case).


Jan 1, 1970
When you go to tie in the battery source of power, consider adding a
switch to select between either the rectified power from the AC/DC
converter or battery power.
Alternately you can add two rectifying diodes that can handle the
current, ex. a 1N4001 diode. The rectifying diodes only allow current
flow in one direction. So without needing to throw a switch, power to
the speakers can come from the AC/DC or batteries. In this
configuration, the pair of diodes are referred to as ORing diodes.

If a switching method similar to one of the two mentioned above is not
done, there is risk of damaging the output of the existing AC/DC
rectifier *if* the rectification is done with a 3-terminal voltage
regulator such as the LM338. The LM338 has a low output impedance
(resistance). Current from the battery would flow to the speakers and
into the output of the LM338 and potentially damage the part.

Take a look and see if there is a 3-terminal device or just a resistor
and zener diode used for the rectifying. If it's just a resistor and
zener, then you'll just end up wasting a portion of the battery energy
in the zener.

Hopefully you can see better what I am talking about with the text
diagram "drawn" below. Anode-Cathode shows the connections of the
positive and negative sides of the diodes.

AC power-->AC/DC rectifier-->Anode-Cathode--\
/ (if any)
Battery power--------------->Anode-Cathode--/

Adding an switch or pair of rectifier diodes would require cutting the
existing connection between the AC/DC rectifier and the

N. Thornton

Jan 1, 1970
have a set of PC speakers that have an AC adaptor for power. It is
9vAC @ 1000ma. I know little about electronics, but I would like to be
able to make these speakers battery powered, even if only for a couple
of hours. What batteries/parts should I look for to put this together?
Thanks in advance

Its a simple question. The simple answer is you'll want a 12v battery,
or 8x D cells in series. And a plug to fit into your speaker power

Regards, NT