Can i take two wallwart power supplies (the AC to DC variety) and just
tie them together in series and parallel to make a cheap diy variable
powersupply.

I am thinking of getting a cheap variable DC 12V ($20 at Fry's), and
then adding a universal DC adapter with up to 12 v also. So if i wire
these in series or parallel or whatever, can i say add 3 v DC to 6 v Dc
to get a usable 9v DC? Or is there gonna be some law of electronics
broken?

thanks for your very expert consulting

Consider this instead - $19 from Radio Shack
http://tinyurl.com/l8tjv


wrote:
Can i take two wallwart power supplies (the AC to DC variety) and just
tie them together in series and parallel to make a cheap diy variable
powersupply.

I am thinking of getting a cheap variable DC 12V ($20 at Fry's), and
then adding a universal DC adapter with up to 12 v also. So if i wire
these in series or parallel or whatever, can i say add 3 v DC to 6 v Dc
to get a usable 9v DC? Or is there gonna be some law of electronics
broken?

thanks for your very expert consulting

Bennett Price wrote:
Consider this instead - $19 from Radio Shack
http://tinyurl.com/l8tjv






my story is that i need 15v and 16v to power 2 different pc scanners.
Local stores only have up to 12 v pot variable or 12v universal
variable/switchable. So I figure buy the pot variable and just tie it
to the various adapters I already have laying around the house.
So i am planning to get my variable and wire it to say a 9v adapter and
add 6v with the variable. In theory that should add up to 15v to power
my flatbed scanner. I am thinking though that compound ripples off the
rectifiers or something like that would cause a quantum superstring
superorder megaohmachronicle power surge. I am very wary of these
non-linear chaos electron interactions. Or perhaps synergistic effects
from reactance and dilitheum crystal interactions might blow the power
core. Not that i care about the power core, i more concerned about our
rations of scotch.






wrote:
Can i take two wallwart power supplies (the AC to DC variety) and just
tie them together in series and parallel to make a cheap diy variable
powersupply.

I am thinking of getting a cheap variable DC 12V ($20 at Fry's), and
then adding a universal DC adapter with up to 12 v also. So if i wire
these in series or parallel or whatever, can i say add 3 v DC to 6 v Dc
to get a usable 9v DC? Or is there gonna be some law of electronics
broken?

thanks for your very expert consulting

Sam Goldwasser wrote:
writes:

Can i take two wallwart power supplies (the AC to DC variety) and just
tie them together in series and parallel to make a cheap diy variable
powersupply.

I am thinking of getting a cheap variable DC 12V ($20 at Fry's), and
then adding a universal DC adapter with up to 12 v also. So if i wire
these in series or parallel or whatever, can i say add 3 v DC to 6 v Dc
to get a usable 9v DC? Or is there gonna be some law of electronics
broken?

If they are in series and both on, then it may work within their current
ratings.

But think about what happens if one of them is not powered on.





would primary coil windings get blown open if the second unit was off?
Would any power surge happen to the total output? I wouldn't want to
blow the device powered off my budget diy supply. I know i can make one
diy for the same money, but i am too lazy and the variable at fry's had
something like 2 or 3 amps which i need.

i don't want to buy a real variable now cause i don't know anything
about electronics yet and i don't know what is a good investment for my
needs.

is there any ripple off AC adapters? Do i have to worry about compound
inductance, reactance, stuff like that which i don't know anything
about. Now i am scaring myself. I guess i would have to research this
myself. I suppose that I could use as a reference two batteries tied in
parrallel or series, then compare the waveforms to the compound
adapters. Shouldn't take too long.

I hope this never blows up my guitar effects boxes!





--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

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.

wrote:
Sam Goldwasser wrote:
writes:

Can i take two wallwart power supplies (the AC to DC variety) and just
tie them together in series and parallel to make a cheap diy variable
powersupply.

I am thinking of getting a cheap variable DC 12V ($20 at Fry's), and
then adding a universal DC adapter with up to 12 v also. So if i wire
these in series or parallel or whatever, can i say add 3 v DC to 6 v Dc
to get a usable 9v DC? Or is there gonna be some law of electronics
broken?
If they are in series and both on, then it may work within their current
ratings.

But think about what happens if one of them is not powered on.





would primary coil windings get blown open if the second unit was off?
Would any power surge happen to the total output? I wouldn't want to
blow the device powered off my budget diy supply. I know i can make one
diy for the same money, but i am too lazy and the variable at fry's had
something like 2 or 3 amps which i need.

i don't want to buy a real variable now cause i don't know anything
about electronics yet and i don't know what is a good investment for my
needs.

is there any ripple off AC adapters? Do i have to worry about compound
inductance, reactance, stuff like that which i don't know anything
about. Now i am scaring myself. I guess i would have to research this
myself. I suppose that I could use as a reference two batteries tied in
parrallel or series, then compare the waveforms to the compound
adapters. Shouldn't take too long.

I hope this never blows up my guitar effects boxes!





--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

"Bennett Price" wrote in message
et...
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

Dave D wrote:
"Bennett Price" wrote in message
et...
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...

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.




wrote:
Dave D wrote:
"Bennett Price" wrote in message
et...
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...

Bennett Price wrote:
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.





you can probably just reverse the leads on one of the connections. So a
parallel circuit/device goes minus plus, the other parallel device goes
plus minus. The classic reverse parallel dive. Guess though these would
have to share current. Maybe those professional power supplies devices
are isolating the ground for some reason. Perhaps for less noisy
signals. Is it possible to have a positive ground? Or is that just as
Seussian as DC peaks? Thanks for your replies by the way.

I ordered a book by Witte on electronics instruments. Keeps on getting
canceled and now the shipping is slow cause i am buying one of those
limited distributed (illegal to possess in the west) Hindu pulp mass
copies of copyrighted western textbooks. You can often find them at
bookfinder4u.com.




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.






i thought about that but decided on the variable 12 v cause its only 20
dollars and a 16v adapter would cost at least that much. Although i
risk burning my house down with bad soldering connections, i also gain
not having to buy all these little wallwarts i have. I think i'm gonna
need a 6v soon too.







wrote:
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

wrote:
Bennett Price wrote:
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.

Distintinguish between ground and minus. Ground in electronic equipment
like
radios and PCs can be either positive or negative. If the negative pole
of a power supply in a radio is tied to the metal chassis (or the common
areas of a PC board, then you can say ground is negative. Alternately,
if the supply's positive voltage is connected to the chassis or the
common areas of a PC board, you can talk about a positive ground.
In a PC, which uses both positive and negative 12 volts, each is
measured in relation to ground (chassis/common) - thus if you connect a
voltmeter's black/negative lead to the chassis, you'll measure +12 at
certain points and -12 at others. If you clip the voltmeter to the +
and - wires, you'll measure 24 volts.

Have you considered a trip to your local public library for an
elementary book on electricity?



you can probably just reverse the leads on one of the connections. So a
parallel circuit/device goes minus plus, the other parallel device goes
plus minus. The classic reverse parallel dive. Guess though these would
have to share current. Maybe those professional power supplies devices
are isolating the ground for some reason. Perhaps for less noisy
signals. Is it possible to have a positive ground? Or is that just as
Seussian as DC peaks? Thanks for your replies by the way.

I ordered a book by Witte on electronics instruments. Keeps on getting
canceled and now the shipping is slow cause i am buying one of those
limited distributed (illegal to possess in the west) Hindu pulp mass
copies of copyrighted western textbooks. You can often find them at
bookfinder4u.com.



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.






i thought about that but decided on the variable 12 v cause its only 20
dollars and a 16v adapter would cost at least that much. Although i
risk burning my house down with bad soldering connections, i also gain
not having to buy all these little wallwarts i have. I think i'm gonna
need a 6v soon too.







wrote:
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

Bennett Price wrote:
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.

Distintinguish between ground and minus. Ground in electronic equipment
like
radios and PCs can be either positive or negative. If the negative pole
of a power supply in a radio is tied to the metal chassis (or the common
areas of a PC board, then you can say ground is negative. Alternately,
if the supply's positive voltage is connected to the chassis or the
common areas of a PC board, you can talk about a positive ground.
In a PC, which uses both positive and negative 12 volts, each is
measured in relation to ground (chassis/common) - thus if you connect a
voltmeter's black/negative lead to the chassis, you'll measure +12 at
certain points and -12 at others. If you clip the voltmeter to the +
and - wires, you'll measure 24 volts.

Have you considered a trip to your local public library for an
elementary book on electricity?






sorry for all the chat, I have already purchased some 12 textbooks on
electronics but i am avoiding my basic electronics book that i had more
than 15 years ago already cause basic electronics is more difficult
than advanced electronics to me. I am pretty much using Electronics
Workbench to get me past all the math and common sense. Sure i'm gonna
get electrocuted some day......but if i ground myself at all times, the
most i'll lose are a few eyebrows and maybe a few tongue taste buds and
ear follicles. I just won't do electrical that's all. Stick to digital
low volts stuff for now. Avoid industrial robotics.

at any rate, i ended up parchasing a cheap switcheable universal cause
the variable at fry's turned out to be a switcheable. So i just went
cheap and will save my money for a good Elenco or something affordable
yet professional. I'm gonna run this through my scope and tell you all
what the ripple is on single then coupled power supplies.

thanks for your help. Really appreciated it cause i did in fact review
my basic electronics book (among others) and it didn't have anything on
DC designs.








you can probably just reverse the leads on one of the connections. So a
parallel circuit/device goes minus plus, the other parallel device goes
plus minus. The classic reverse parallel dive. Guess though these would
have to share current. Maybe those professional power supplies devices
are isolating the ground for some reason. Perhaps for less noisy
signals. Is it possible to have a positive ground? Or is that just as
Seussian as DC peaks? Thanks for your replies by the way.