# How to connect a linear power supply

Discussion in 'Electronic Basics' started by Ant_Magma, Mar 10, 2006.

1. ### Ant_MagmaGuest

I know this may sound like a dumb question but i have a Tracopower TML
5 Watt AC/DC power module and i don't know how to connect them to my
circuit.

The datasheet is available here
http://www.tracopower.com/products/index.htm

For the TML 5 Watt there are pins 1 2 3 at the input and 4 5 6 at the
output side.
1) What is FG? Where do i connect this?
2) Pin 2 and 3 are both AC inputs which do i connect to line, which do
i connect to neutral (from wall outlet)?
3) What is pin 5 (NC)? If i only want +5V do i connect to pin 6 and 5
and if i want +5V & -5V i connect pin 4 and 6?

2. ### DeefooGuest

Which TML do you have? Single 5V (05105) or double +/-5V (05205)?

1. FG means Frame Ground and should be connected to the earth.
2. The datasheet says pin 2 is AC N(eutral) and pin 3 is AC L(ine).
3. NC here means Not Connected. This is for the single supply version only
and you simply do not use this pin. In this case you will have +5V between
pin 6 and pin 4. Pin 4 will connect to your circuit's 0V. For the dual
supply version you will need pin 5 to have +5V between pin 6 and pin 5
and -5V between pin 4 and pin 5. Pin 5 will connect to your circuit's 0V.

--DF

3. ### ChrisGuest

Hi, Ant. I'm not sure if you actually found the data sheet:

http://www.tracopower.com/products/tml.pdf

If you look on page 4 of the datasheet, you see the pinout. On the
input side (pins 1, 2, 3),

1 = FG
2 = AC(N)
3 = AC (L)

On the wall outlet, you have Line (pin 3), Neutral (pin 2), and Ground
or Chassis/Frame Ground (Pin 1).

On the output side, it depends on the model you purchased. By looking
on page 1 of the data sheet, you can see that there are seven 5 watt
models. If you've got a TML05105, there's a single 5V output. Pin 5
is common, pin 6 is the +5V. Pin 4 is NC (No Connect). If you've got
a TML05205, it has both a +5V and -5V available. For the dual +/-5V
model, pin 5 is still common and pin 6 is still +5V. However, on that
model, pin 4 is -5V.

Good luck
Chris

5. ### Ant_MagmaGuest

Mine is a single TML05105.

I think i got the old datasheet coz mine did not have the (L) and (N).
So for my case i just connect the pin4 and pin6 to get 5V.

Now another problem. I'm using this PSU for this circuit:
http://www.belfuse.com/Data/DBObject/0557-7700-xx.pdf

It's Belfuse's powerline signal coupler. On page 3 (Ethernet product),
the PSU is connected parallely after the MOV to the L and N. Here, the
Earth of the wall outlet is not used.

So how do i connect FG?

Connect FG and pin2 together and connect them to N?

6. ### ChrisGuest

Hi, Ant. I would assume there's internal shielding and circuitry in
the switch-mode power supply connected to FG that helps reduce EMI/RFI
emissions. If this were an actual engineering project, you would have
to be very concerned with FCC emissions testing, and this seemingly
trivial question would take on a lot of significance. In the real
world, this can easily be a project killer, and is one major reason why
many engineers use canned switchers instead of just rolling their own
for low volume applications.

In a college lab, you won't have the equipment available to measure
emissions, and I guess you don't have the time to go down this rabbit
trail anyway, so just gloss it. For now, just use a 3-conductor line
cord, and connect GND on the line cord to FG.

Remember that, unless you've got a handful of these, you may want to
use another method of powering your prototype through the initial
stages. Although this switcher data sheet says it's got overload and
short circuit protection, a mistake is pretty expensive, particularly
if you've only got one of them (another lesson -- in a development
project, always get a couple of everything).

Good luck
Chris

7. ### Ant_MagmaGuest

But in the Belfuse coupler schematics they only use the L and N lines.
And the N line in this case is used as the reference potential or
ground.

I just want to be sure. Are you suggesting that i use the G line as
well just to connect it straight to FG?

Yes.

Chris

9. ### Ant_MagmaGuest

Thanks Chris.

Now another thing, in theory the electronics that i learn on paper,
there's always ground for the current to return.

Based on Bel's coupler diagram, i would assume the -Vout of the PSU
would be the current's return path where i connect all my grounds to,
correct?

If so, now with the extra G line connected to the FG of the power
supply, which would be my ground now?

10. ### ChrisGuest

Pin 1 is FG. That is added on the primary side of the switcher for
reasons stated above.

The switch-mode power supply has transformer isolation between the
primary and the secondary. For the 5V power supply on the secondary,
pin 5 is common or the current return path. There is no connection
between the primary side and the secondary side.

Ground means many things in electronics, including the return path for
the current from the power supply. FG means frame ground.

Since you're using Google groups, search the word "ground" in this
newsgroup for numerous discussions on this subject.

Chris

Chris

11. ### Ant_MagmaGuest

Thanks Chris, but since i'm using the SINGLE version and NC is not
connected i should use pin 4 correct?

12. ### ChrisGuest

Ant, it's all in the datasheet. Here's a sketch (view in fixed font or

|
| Ground .---------.
| (Green) FG| |
| >---------o 1 | +5V
| | 6 o--------> Your
|Neutral AC(N)| | Circuit
| >---------o 2 5 o-------->
|(White) | | COM
| AC(L)| 4 o No Connect (that means leave it open, don't
connect anything)
| >---------o 3 |
| Line | |
|(Black) '---------'
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

NC means No Connect. If you're making a perfboard, don't solder
anything to pin 4. If you're making a PC board, make a pad to allow
the pin to be soldered to the board, but don't connect anything to that

Frequently, NC pins will be used by the manufacturer as test points for
QC to check something inside the black box post-production. Sometimes
there's actually nothing connected to NC pins. But there's no law that
says they can't make another version that uses that NC pin for
something else, so always leave it alone. NC means No Connect.
Period.

Ant, read the data sheet. If you don't understand it, reread it until
you understand it.

Just do the work. There really isn't a substitute, unless you want to
subcontract the job to someone else.

Chris

13. ### Ant_MagmaGuest

Are we having the same datasheet? Mine only have the specifications and
the dimensions.

Sorry Chris, i did not intent look lazy or annoy anyone.

It's just that it's my first time doing such a project and i'm just
trying to get everything right before i start soldering and putting it
together.

14. ### ChrisGuest

Hi, Ant. Three days ago I gave you the link to the data sheet:

http://www.tracopower.com/products/tml.pdf

which requires two more mouse clicks from the page you referenced.
Just look at the posts above this one. Since it's a .pdf file, it also
you're using M\$ Windows, right-click on the link, and click "Save
Target As..." instead of just clicking on it.

This fairly complete data sheet goes into more detail than typical on
the power supply. There should be enough there to use the AC-to-DC
module.

No offense, Ant. Prototyping is a bit of a chicken-egg thing when
you're dealing with SMT components, I know. But you're also under

Chris