Help on circuit layout

C

Chris

Jan 1, 1970
0
I have drawm up a power supply on eagle, on bread board it all works
fine, but when i did a single layer pcb it didn't. Now one thing i
noticed if i use autoroute the current doesn't seem to take the same
path as it does on breadboard, it seems to run here and there... does
this matter?

Schematic: http://chrispol.ath.cx:8080/power.jpg

Board Layout: http://chrispol.ath.cx:8080/powerboard.jpg

C

Clarence

Jan 1, 1970
0
Your AC input, "X1" should be connected to pin 2, not as shown on pin 3!

C

Clarence

Jan 1, 1970
0
Just curious:
If your qualified to write a (really) basic book on electronics, shouldn't you
at least be able to trouble-shoot a simple power supply?

G

Graham Knott

Jan 1, 1970
0
Clarence said:
Just curious:
If your qualified to write a (really) basic book on electronics,
shouldn't you at least be able to trouble-shoot a simple power supply?

He didn't ask for help troubleshooting!

the current doesn't seem to take the same
Try to be more positive with you criticisms and life can only get better.
Best regards.

C

Clarence

Jan 1, 1970
0
Graham Knott said:
He didn't ask for help troubleshooting!

the current doesn't seem to take the same

Other than the lines should probably be a little wider so a Power Supply to
minimize resistance it should have only a minimal effect?
Try to be more positive with you criticisms and life can only get better.
Best regards.

" I have drawn up a power supply on eagle, on bread board it all works
fine, but when I did a single layer pcb it didn't."

Sounds like a trouble shooting problem to me.
Also, the Schematic showed the input AC connector connected wrong!

Besides it was a valid question, not criticism.

While we are at it, why are 'YOU' so RUDE?

C

Clarence

Jan 1, 1970
0
Clarence said:
Other than the lines should probably be a little wider so a Power Supply to
minimize resistance it should have only a minimal effect?

" I have drawn up a power supply on eagle, on bread board it all works
fine, but when I did a single layer pcb it didn't."

Sounds like a trouble shooting problem to me.
Also, the Schematic showed the input AC connector connected wrong!

Besides it was a valid question, not criticism.

While we are at it, why are 'YOU' so RUDE?

I see that I was not replying directly to the OP due to the poor cropping of
the post you replied to with a curt "NO". Sorry about that. and your tag line
was in the way. Checking it made me question the need for the original post. I
see now that your RUDE response was because you missed the problem and wanted
to strike out in anger at someone.

I didn't mean to get in the line of fire.

BTW, there are a lot of GOOD books for beginners!

G

Graham Knott

Jan 1, 1970
0
Clarence said:
Other than the lines should probably be a little wider so a Power
Supply to minimize resistance it should have only a minimal effect?

" I have drawn up a power supply on eagle, on bread board it all works
fine, but when I did a single layer pcb it didn't."

Sounds like a trouble shooting problem to me.
Also, the Schematic showed the input AC connector connected wrong!

Besides it was a valid question, not criticism.

While we are at it, why are 'YOU' so RUDE?

Oh dear,another troll.
I always give my best regards to trolls hoping that it makes their life
just a little bit happier.
Best regards Clarence.

C

Clarence

Jan 1, 1970
0
Oh dear,another troll.
I always give my best regards to trolls hoping that it makes their life
just a little bit happier.
Best regards Clarence.

No, I'm not, but I know one when I encounter one!

You seem to have a problem relating to people.

P

petrus bitbyter

Jan 1, 1970
0
Chris said:
I have drawm up a power supply on eagle, on bread board it all works fine,
but when i did a single layer pcb it didn't. Now one thing i noticed if i
use autoroute the current doesn't seem to take the same path as it does on
breadboard, it seems to run here and there... does this matter?

Schematic: http://chrispol.ath.cx:8080/power.jpg

Board Layout: http://chrispol.ath.cx:8080/powerboard.jpg

Printlayout is almost an art in itself and an autorouter is all but an
artist. This print is bad in two ways: The placement of some components is
wrong and the traces are improperly drawn and to thin. I don't want to
cover the whole print but I'll give some examples.

- The trace from the cathode D1 branches. One trace goes to the capacitors,
the other to the regulator. That's wrong. The trace should go from the diode
to the capacitors and then from the capacitors to the regulator.
- The 100nF decoupling capacitors should be near the regulators. Especially
a 7912 can go oscillate like hell when not carefully decoupled. Check the
datasheets for it.

An autorouter is not the correct tool to design printed circuit boards like
this. Its rules do not care for the rules of even this simple power suply
design.

petrus bitbyter

C

Clarence

Jan 1, 1970
0
My name is Graham Knott and I teach Electronics and Microcomputing in a third
rate school at Cambridge Regional College, situated in the city of Cambridge,
England. I need you money so send me $20 USD for my little reader. Send money to: Graham Knott 27, Edinburgh Road Cambridge CB4 1QR UK phone 01223 502751 Graham, Did I understand this right? J James T. White Jan 1, 1970 0 Chris said: I have drawm up a power supply on eagle, on bread board it all works fine, but when i did a single layer pcb it didn't. Now one thing i noticed if i use autoroute the current doesn't seem to take the same path as it does on breadboard, it seems to run here and there... does this matter? Schematic: http://chrispol.ath.cx:8080/power.jpg Board Layout: http://chrispol.ath.cx:8080/powerboard.jpg Chris, Some observations: 1) Your schematic and board don't seem to match. For example there are 6 diodes on the board and only 4 on the schematic. Also, the input power connector seems to have all three pins connected on the board and only 2 connected on the schematic. 2) Have you verified the schematic and layout pin connections for all the library components you have used against the component data sheets for the parts you are using? It might seem strange, but I have seen an error here cause lots of problems. 3) As some of the other responders have indicated, you should be using larger traces for a power supply. You would also have better luck keeping the traces short, by manually routing something this simple. You might have to add a wire jumper here or there, but that is better than letting the autorouter run a trace all around the board as it did for the input to your 7812. If you really must use Eagle's autorouter, you should define a Net Class for your power traces before turning the autorouter loose. 4) You might also try the Eagle news groups (eagle.support.eng or eagle.userchat.eng). Since your circuit isn't a top secret design, consider posting copies of your Eagle .brd and .sch files to make it easier for other Eagle users to help you. At least that way, one could turn off the silkscreen layer to see where the traces really go. Good luck. I'd be interested to hear what the problem was when you find it. J Jonathan Kirwan Jan 1, 1970 0 Oh dear,another troll. I always give my best regards to trolls hoping that it makes their life just a little bit happier. I've long since permanently killfiled him. When I get to read him quoted by others, though, I continue to see the sharp wisdom of that decision. Jon D David Harmon Jan 1, 1970 0 On Sat, 6 Nov 2004 17:26:21 -0600 in sci.electronics.basics, "James T. White said: Some observations: 1) Your schematic and board don't seem to match. For example there are 6 diodes on the board and only 4 on the schematic. Also, the input power connector seems to have all three pins connected on the board and only 2 connected on the schematic. This strikes me as very odd. In my experience, that's the sort of thing Eagle gets right 100% of the time. You draw the schematic, then tell Eagle to "create board from schematic". It gives you a created board file with all the parts, and airwires for all the net-connections. However you proceed to move the parts around and route the connections, the airwires don't go away until you are done. C Clarence Jan 1, 1970 0 wrote: That is funny. I kill filed him and haven't seen him until I cleared my Kill file after the election. But he is so sure I can't see him, because he was so objectionable. So he is still being a jerk? Right? P Peter Bennett Jan 1, 1970 0 I have drawm up a power supply on eagle, on bread board it all works fine, but when i did a single layer pcb it didn't. Now one thing i noticed if i use autoroute the current doesn't seem to take the same path as it does on breadboard, it seems to run here and there... does this matter? Possibly... Schematic: http://chrispol.ath.cx:8080/power.jpg Board Layout: http://chrispol.ath.cx:8080/powerboard.jpg First, I see an error on the schematic - the AC ground should come from pin 2 of the connector, not pin 3. The board layout seems to have six diodes, but there are only four on the schematic??? The board layout is poor - the capacitors at the input and output of the regulators should be placed very close to the regulators - you want short fat tracks between the hot side of the capacitors and the regulator, and between the ground side of the capacitors and the regulator. I can't see how you get from C2+ to IC2-in. Autorouters can be useful, but they can also seriously mess up the routing - things may be connected, but the tracks will go all over the countryside. Strangely, they will often do a worse job on a simple board like this than on a more complex board. I don't know if Eagle has an auto-placer - but if so, don't bother with it. Autoplacers were invented to appease the marketing department, and rarely do anything useful, even on high-end CAD systems. I don't know what currents you expect to have on this board, but as a matter of course, I would use .050, or even .100, tracks in a power supply. There is lots of room on the board for Really Big tracks. A comment on schematic drawing conventions - I consider it Bad Practice to have 4-way junctions on a schematic - if the connection dots go fuzzy (as they will after a few photocopies), it will be unclear whether C1- and C5+ are just connected to each other, or if they are also connected to ground. I would move the whole -12 regulator section right one grid position, so that you only have 3-way connections - that would make it perfectly clear that C1- and C5+ connect to ground. -- Peter Bennett, VE7CEI peterbb4 (at) interchange.ubc.ca new newsgroup users info : http://vancouver-webpages.com/nnq GPS and NMEA info: http://vancouver-webpages.com/peter Vancouver Power Squadron: http://vancouver.powersquadron.ca G Graham Knott Jan 1, 1970 0 Clarence said: My name is Graham Knott and I teach Electronics and Microcomputing in a third rate school at Cambridge Regional College, situated in the city of Cambridge, England. I need you money so send me$20 USD for

Send money to:

Graham Knott 27, Edinburgh Road Cambridge CB4 1QR UK phone 01223
502751

Graham, Did I understand this right?
PLONK!

J

JeffM

Jan 1, 1970
0
3)As some of the other responders have indicated, you should be using
larger traces for a power supply. You would also have better luck keeping
the traces short, by manually routing something this simple.
You might have to add a wire jumper here or there, but that is better than
letting the autorouter run a trace all around the board as it did for the
input to your 7812. If you really must use Eagle's autorouter, you should
define a Net Class for your power traces before turning the autorouter loose.

4)You might also try the Eagle news groups (eagle.support.eng or
eagle.userchat.eng). Since your circuit isn't a top secret design,
consider posting copies of your Eagle .brd and .sch files to make it easier
for other Eagle users to help you. At least that way, one could turn off
the silkscreen layer to see where the traces really go.
James T. White

Chris,
A lot of good stuff from James.
There is a school of thought on etching PCBs
that says the less copper you etch away, the more ecomomical the design;
make 'em as fat as clearance allows. (Your etchant lasts longer.)
Beefier copper is rarely a bad idea.

BTW, the EAGLE Autorouter never impressed me
--not even on a shortest-route basis.
As petrus said, to do a good job,
an autorouter has to know a lot of rules about physics
and the more you do before turning it loose, the better it does.

Replies
16
Views
757
Replies
4
Views
330
Replies
5
Views
890
Replies
25
Views
1K
Replies
6
Views
878