# 9 + 9 = 18 ?

Discussion in 'Misc Electronics' started by Virginia Belle, Nov 19, 2003.

1. ### Virginia BelleGuest

I Know that this is a dumb question but, I am curious anyway.

Lets just say that I need an 18 volt DC power source and that the source
has to come from one of those transformers? that plug into the wall and
change AC to DC.

What if I only have two of those transformer devices that are 9 Volts
DC each.

Now, If I cut the insulation off of the ends of both of those
transformers, take the two wire ends from each and twist the 4 ends
together to make two again, plug them in, will THAT make me the 18 volts
that I need?

9 + 9 makes 18 doesn't it?

Thank You
Brenda

2. ### Rein WiehlerGuest

no, that will be 9 volts only.
you cann cut the connectors of and wire the negative of on 9v adapter
to the positve of the other adapter. remember you have to "add" the
voltages

3. ### Fritz SchoerghuberGuest

yes, but ONLY THIS WAY:

source#1 +9V --------------------------------- +18V out
-9V -----+
|
| (connect the wires)
source#2 +9V -----+
-9V --------------------------------- GROUND
HTH fritz

what i think you are talking about is paralel connection. this would double
the power but woudlnt increse the voltage.
you need to make a serial conection. each power adapter has a positive and
negative wire. you need to connect positive wire
of one adapter to negative wire of the other.the voltage betven two
remaining(unconected) wires will be 18.

5. ### CWattersGuest

You need to connect them together in series not paralel.....but first ...

If the mains adaptor has an earth pin you need to check that neither of the
output wires is connected to the earth pin.

If it is connected then you will damage one of the power supplies.

6. ### Byron A JeffGuest

-I Know that this is a dumb question but, I am curious anyway.
-
-Lets just say that I need an 18 volt DC power source and that the source
-has to come from one of those transformers?

A bit more than just a transformer.

- that plug into the wall and
-change AC to DC.

Commonly known as a "wall wart"

-
-What if I only have two of those transformer devices that are 9 Volts
-DC each.

The you probably have a problem.

-
-Now, If I cut the insulation off of the ends of both of those
-transformers, take the two wire ends from each and twist the 4 ends
-together to make two again, plug them in, will THAT make me the 18 volts
-that I need?

No. It'll most likely blow one or the other of the wall warts depending on
how you wired it.

Your best bet is to get the correct supply for what you need. 18V is commonly
used by laptops so finding such a supply shouldn't be difficult.

BAJ