Supply Power

AtomSoft

Well-Known Member

• Feb 16, 2010

• #1

Hello people im back heh...

I need to power a pic which is the simplest thing in the world when using a normal AC/DC Adapter. The issue i have here is this will be placed in my wall..

I want to use a transformer or some way stepping down our 125v POWER LINES. I will be placing the pic in a box :

**broken link removed**

It takes about have that box for my circuit.. I need the transformer or step down power stuff to fit in the other half.. i have about 3sq in left for it.... do you think its possible to make the step down supply or buy a transformer to fit in there for under $10 USD...

The circuit i have already has a LM7805 so it can handle up to 20v DC input i think...

 

K

KMoffett

Well-Known Member

• Feb 16, 2010

• #2

How much current?

Ken

 

AtomSoft

Well-Known Member

• Feb 16, 2010

• #3

the 7805 supply 1A so i would like it to be 1A but 500-800mA would do

 

AtomSoft

Well-Known Member

• Feb 16, 2010

• #4

let me run a test and measure max current usage 1min

 

Last edited: Feb 16, 2010

AtomSoft

Well-Known Member

• Feb 16, 2010

• #5

300mA max is used so to be safe 400mA - 500mA

 

G

gerty

Member

• Feb 16, 2010

• #6

How about an old cellphone charger? it might be small enough. The box you show is called a single gang handy box, you could go to a 4x4 , or a 4 11/16 square. They are also available in cast aluminum or pvc.

 

AtomSoft

Well-Known Member

• Feb 16, 2010

• #7

i was thinking about that but the issue is i might have this mass produced like 100 so i wanted a good source for parts

 

AtomSoft

Well-Known Member

• Feb 16, 2010

• #8

ill make that my last resort heh.. if it cost too much to do ill buy 100 chargers and take apart and incorp it into my design

 

K

KMoffett

Well-Known Member

• Feb 16, 2010

• #9

The only thing I can think of is to gut a 5v SMPS cellphone charger, and bypass the 7805. All the ones I've found are regulated. They run between $.99 and $2.99 at thrift stores around here. The current ratings are usually 700mA for the smallest ones and up to 2.0A for the slightly larger ones. I use a coping saw to cut "almost through" the case at the glue lines, then use a big flat blade screwdriver to pop them open.

Ken

 

Hero999

Banned

• Feb 16, 2010

• #10

What size is the box?

How much power do you need?

Does it need to be isolated? Would a transformerless power supply do?

Obviously that metal box will have to be earthed.

 

AtomSoft

Well-Known Member

• Feb 16, 2010

• #11

Thats what ill have to do then.. found this:

**broken link removed**

or

**broken link removed**

 

AtomSoft

Well-Known Member

• Feb 16, 2010

• #12

Hero999 said:

What size is the box?

How much power do you need?

Does it need to be isolated? Would a transformerless power supply do?

Obviously that metal box will have to be earthed.

Click to expand...

I have 3 square inches at a height of 1inch... for the power supply.
I need 5v 500mA as the final outcome...
Transformerless is fine.
Earthed? (grounded)?

The main idea or outcome is 5v @ 300mA minimum needed.

EDIT:

Going to pharmacy be back in 30min

 

Last edited: Feb 16, 2010

K

KMoffett

Well-Known Member

• Feb 16, 2010

• #13

That second one looks like it has screws to hold on the back. That would make disassembly easy.

Ken

 

Hero999

Banned

• Feb 16, 2010

• #14

The current is too high for a transformerless PSU and it's too small for a linear PSU so you're restricted to an SMPS.

The most cost effective option is probably to buy a small plug-top SMPS and use the PCB, as mentioned about.

Earthed = grounded.