# Wall Wart Power Supply query.

#### biferi

Joined Apr 14, 2017
394
I Live in the USA so My House Outlet is Rated 120 VAC at 15 Amps.

I have a Project I Made and I need a Wall Wart that will Turn the 120 VAC 15 Amps into 12 VDC 2. Amps.

And I Find a lot of these on Amazon but they are some what Big.

Can You help Me Find any that are Small in Size?

Do they Make Mini or Micro ones?

#### MrChips

Joined Oct 2, 2009
31,067
It would appear that you are still struggling with understanding this 15A thing.
Forget the 15A. Calculate the power requirement.

Your house wiring is designed to handle 15A.
Power = I x V = 15A x 120V = 1800W
That kind of power will burn your house down.

You only need 2A x 12V = 24W
(24W is still quite a lot of power. You can burn your fingers badly on a 24W soldering iron.)
Look for a wallwart that supplies 12V and 2A max.
The current rating is the maximum that it can supply. You take whatever current you need from 0A to 2A.

#### Ramussons

Joined May 3, 2013
1,417
And I Find a lot of these on Amazon but they are some what Big.
What are the "these" you searched for? Can you please elaborate?

Joined Feb 20, 2016
4,503
Can You help Me Find any that are Small in Size?
That is a very vague statement.
What physical size do you need?
And a 12V 2A supply will draw about 0.2A from the 120V mains, so you could run about 75 of them from a 120V 15A supply.

#### crutschow

Joined Mar 14, 2008
34,827
The size is somewhat constrained by the required output power.
Why do you need it small?

Joined Jul 18, 2013
28,820
And I Find a lot of these on Amazon but they are some what Big.

Can You help Me Find any that are Small in Size?
I suspect you are not going to get anything smaller than the 12v. 2a. AMAMAX versions see Amazon etc.
If it is plugged into the wall, why do you need it miniature?

#### ronsimpson

Joined Oct 7, 2019
3,203

#### Audioguru again

Joined Oct 21, 2019
6,782
I made a little amplifier for my TV. This amplifier is powered from a very small switching 12V/2A wall wart that came with a modem. The wall wart is the same small size and has a similar circuit as a charger for a cell phone.

#### biferi

Joined Apr 14, 2017
394
Well any AC to DC Transformer is Fat and Big and I get this they have Coils of Wire to Convert the High Voltage to a Low Voltage.

So do they not make any the Size of a CellPhone Charger?

Your CellPhone Plugs into a Charger that is Small and Plugs into the Wall.

And the CellPhone Charger Converts the 120 VAC to 5. VDC at 1. Amp for Charging.

Am I Right on this?

#### crutschow

Joined Mar 14, 2008
34,827
So do they not make any the Size of a CellPhone Charger?

Your CellPhone Plugs into a Charger that is Small and Plugs into the Wall.

And the CellPhone Charger Converts the 120 VAC to 5. VDC at 1. Amp for Charging.

Am I Right on this?
You are not considering the power difference.
A 12V, 2A charger outputs 24W of power, nearly 5 times the 5W of the cellphone charger.
You can't get that much extra power without increasing the size.
This is probably about as small as they get.

Joined Jul 18, 2013
28,820
This is probably about as small as they get.
About the same size as the Amazon Amamax one I referred to.

#### Audioguru again

Joined Oct 21, 2019
6,782
I have a cell phone charger rated at 5V/1A and a wide AC voltage range. It is the same size as the small 12V/2A one shown in post #11. I have some tiny cell phone chargers that are 5V/1A.

#### MrChips

Joined Oct 2, 2009
31,067
There are different wall adapter designs.

A transformer is big and heavy and usually designed for a fixed AC line voltage, e.g. 110/120VAC.

A transformerless adapter is smaller and lighter. It usually is able to accept a range of AC line voltages from 80-240VAC.

#### LowQCab

Joined Nov 6, 2012
4,290
The tiny Phone-Charger type Power-Supplies are usually a "Switching" design,
rather than a big fat, heavy, Iron-Cored-Transformer type.

Sometimes the Switching-type can be very crude and electrically "noisy",
which is a trait that You do not want in an Audio-Amplifier Power-Supply.

I would use a much higher quality "Laptop-Computer Power-Supply"
and then build a nice Filtering/Regulating Circuit for it.
They're usually right around ~20-Volts, and ~2 to ~3 Amps, ( ~50 to ~75 Watts ),
and they are probably around ~$1.oo each at your local Goodwill Thrift Shop. The ~20-Volt Output rating provides plenty of headroom for Voltage-Regulation. They are usually isolated from the Mains-Voltage, and so, they may be easily used to create a "Split-Supply" by using 2 of them in series. These will also make a great, low Current, Car-Battery-Charger. . . . #### dendad Joined Feb 20, 2016 4,503 EDIT: wrt post #9.... The transformers in a switch mode supply are a lot smaller because they operate at a much higher frequency. The lower the frequency, the larger the core needs to be so, no, they cannot make a 60hz power transformer as small as the 100khz (or even 1Mhz) transformers used in some switch mode supplies. In fact, a 60hz transformer can be a bit smaller than a 50hz of similar power rating. The result of all that is if you need really small, you will need to look into switch mode supplies. Last edited: #### MaxHeadRoom Joined Jul 18, 2013 28,820 The posts #6,#7,#10,#11,#13 all refer or show SMPS supplies. #### bassbindevil Joined Jan 23, 2014 838 Visit some thrift stores. There are usually plenty of power bricks there. I paid$1 at "Bibles For Missions" for a Wii brick that does 12V at 3.7 amps, and presumably is much better quality than the alphabet-soup-brand black boxes from Amazon.
Other sources are yard sales, flea markets, recycling yards.

Joined Jan 15, 2015
7,577
I have a Project I Made and I need a Wall Wart that will Turn the 120 VAC 15 Amps into 12 VDC 2. Amps.
Aside from everything mentioned there should be another consideration. If your load is 2.0 amps you will want your supply to have the ability of supplying a current in excess of 2.0 amps. You really do not want to draw 2.0 amps from a supply rated at a maximum current of 2.0 amps. You want a little overhead in there. You want about a 20% comfort or overhead. For a continuous 2.0 amp load I would be looking for a 2.5 amp rated supply.

Ron

#### Audioguru again

Joined Oct 21, 2019
6,782
My home has 120VAC/15A outlets. My clock radio is plugged into one of them and does not use the entire 120 x 15= 1800W, Instead it uses about 1W (9VDC at 0.11A).

#### ThePanMan

Joined Mar 13, 2020
803
The ones I've seen capable of 12VDC @ 2A are typically 1 1/4" x 2 1/2" x 5".

Someone on this website recommended going to Xfinity stores and asking them for one of their returned 12V wall warts. I've done exactly that. However, Xfinity is starting to go to units that run on 110VAC, not 12VDC. Generally, their return units come back with PS's and they don't reuse them, they just toss them.

If you can't find one at Xfinity then try one of the local satellite stores. There's a chance they might have some units that are 12V powered.

Just so you know, a PS capable of supplying 2A doesn't mean it's going to force your equipment to draw 2 amps. Only means that your equipment can draw UP TO 2 amps. Not more. At least not reliably.