Re: compound variable power supplies--possible?

Some devices have connectors that put the - voltage on the center pin, others put + on the center pin. (For center pin, you can substitute big pin/socket, funny looking pin/socket, yellow pin/socket, etc.)

In your PC, the power supply is generating both +12 and -12 volts - there's an instance where both voltages are needed - rather than just swapping the + and - pins.

It doesn't make much sense to talk of DC peak voltages; ideally,
DC voltage is smooth and doesn't have peaks. AC voltage, on the other
hand, can be measured in several ways (Average, RMS, Peak).

Are you sure that both of your scanners need DC? You said one required
15 volts, the other 16. In all likelihood you could use the same power
supply for both. I'd buy 1 power supply (perhaps from the scanner mfr)
and use it for both. Which to buy 15V or 16V? - whichever is cheaper.




whyzard@xxxxxxxx wrote:
Dave D wrote:
"Bennett Price" <bjpriceNOSPAM@xxxxxxxxxxxxx> wrote in message
news:XsZYf.64870$Jd.38622@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
You can connect two DC adapters in series (not paralle), plus of one to
negative of the other; then add the two voltages together. In your
example, a 6V and 3V will yield 9V If one is turned off, you will not
warp the universe.
No, but it will damage the smoothing capacitor of the adaptor that is not
powered because reverse voltge will be presented across it. It will be
limited to 1.4-ish volts by the bridge rectifier being forward biased, but
it's still not good news.

Dave




this shouldn't be a problem. The variable would have serviceable parts.
the fixed switcheable universal probably isn't serviceable cause all
the parts are in those plastic cases and they are tightly manufactured,
but these are also quite cheap. I can just replace the switcheable and
fix the variable if needs be.

by the way, looking into power supplies more,
why would someone need negative DC volts. They are below the 0 v line
on a scope right?
What uses negative DC? A 50 dollar elenco variable had a spec of -1 to
-15 dc v

seems to me like -15v is still 15 v (0 to peak). Don't really know of
course, that's why i'm asking you...

.

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