Small 120vac to 12vdc transformer

Status
Not open for further replies.

Thread Starter

bd525

Joined Nov 11, 2009
28
What is the smallest transformer (step down) that I can use to take 120VAC to 12VDC? I have project that needs 12vdc, but I am told as one of the requirements is not to use a standard wall wart transformer... Can I use a miniature PCB transmformer? Is there a better way to do this?

Thanks!
 

t06afre

Joined May 11, 2009
5,934
Is this a school project? Because perhaps then your teacher want you to build a simple power supply as part of the learning process. A simple power is made by a transformer,rectifier, filter cap, and linear regulator(s).
Also do not feel afraid to admit that it is a school project. You are welcome to ask your questions here in this forum
 

Thread Starter

bd525

Joined Nov 11, 2009
28
Hey Guys,
Thanks for all your replies!!

No this isnt a school project. I have been playing with electronics as a hobby and one of my personal projects caught wind of my boss and now had become part of a work project. I am learning as I do this so thats why I am asking questions here to get expert input.

I will check out the link here in a few.
 

Thread Starter

bd525

Joined Nov 11, 2009
28
Thanks for the KMoffet, that might work... also I am going to start hunting some wall warts to see what I can find...
 

Audioguru

Joined Dec 20, 2007
11,248
A cheap wall-wart AC-DC adapter has horrible voltage regulation. its output might be 12V with lots of ripple at its rated load current but might have an output voltage of 24VDC at a low current.
 

jls667

Joined Jun 5, 2013
35
Although this is an old thread, I am looking to build or buy a transformer from 120vac to 12vdc. It would need to be relatively small to fit in an outdoor project box. It would need to run a few relays, so it only needs about 100mA. Any ideas?
 

KMoffett

Joined Dec 19, 2007
2,918
Check thrift stores or your friends' junk drawers. Orphan wall plug charger transformers will likely serve your purpose. It they are a little too big, I just "carefully" cut off the plastic case off.

Ken
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
If it is just for relays then presumably you do not really need regulated?
As already mentioned, the older wall warts are unregulated, so don't go by the voltage stated on the cover, the O.C. voltage is usually 60% higher.
You can usually tell them apart by the weight, the older ones have a 50/60 hz mains transformer rather than regulated switching supply.
Regulated wall wart supplies can be had for around $5.00 now, so often it is not worth the effort to make for this size.
Max.
 

jls667

Joined Jun 5, 2013
35
I am not sure how important a regulated supply would be to relays. My relays are 12vdc relays, but they are switching 120vac 7amp motor.
 

Wendy

Joined Mar 24, 2008
23,415
What has happened here is called hijacking. A thread belongs to the OP (original poster). Hijacking is not allowed at AAC. Please start your own thread.
 
Status
Not open for further replies.
Top