First ever PCB design - take a peek?

[ScottM]

I've used PCBExpress to design my first ever board (not quite accurate
- back in the sixties I played with copper clad boards and ferric
chloride solutions, but the results weren't great.)

Before I spend money on having this commercially cut, I'm hoping
someone will take pity on a relative newbie and point out any errors
and stupidities in the board layout. I'm not asking for circuit
analysis - just someone who has the time to look at how I laid the
traces, and point up obvious problems. I've never done two layer
before. It's been a lot of years since I did one layer.

Especially, there are a couple of points at which I have a component's
leg going through the board, and a trace connecting to it on both the
top and bottom layer. I'd like the top and bottom trace connected
whether or not the component is installed, but PCBExpress wasn't
totally clear on whether all holes for components are really cut as
vias. It makes sense that they would be, but I'd rather not find out
the hard way.

Anyway, it's all connectors, DIPs, resistors and caps, and hopefully
not difficult for someone who does this for real to grok and comment
on. Many thanks in advance. I promise to learn from my mistakes.

www.obsessionaudio.com/dimmer2.pcb [if you have PCBExpress]
www.obsessionaudio.com/dimmer2.dxf [which I hope is readable - I
can't tell]

 

[martin griffith]

I've used PCBExpress to design my first ever board (not quite accurate
- back in the sixties I played with copper clad boards and ferric
chloride solutions, but the results weren't great.)

Before I spend money on having this commercially cut, I'm hoping
someone will take pity on a relative newbie and point out any errors
and stupidities in the board layout. I'm not asking for circuit
analysis - just someone who has the time to look at how I laid the
traces, and point up obvious problems. I've never done two layer
before. It's been a lot of years since I did one layer.

Especially, there are a couple of points at which I have a component's
leg going through the board, and a trace connecting to it on both the
top and bottom layer. I'd like the top and bottom trace connected
whether or not the component is installed, but PCBExpress wasn't
totally clear on whether all holes for components are really cut as
vias. It makes sense that they would be, but I'd rather not find out
the hard way.

Anyway, it's all connectors, DIPs, resistors and caps, and hopefully
not difficult for someone who does this for real to grok and comment
on. Many thanks in advance. I promise to learn from my mistakes.

www.obsessionaudio.com/dimmer2.pcb [if you have PCBExpress]
www.obsessionaudio.com/dimmer2.dxf [which I hope is readable - I
can't tell]

haven't had a look, since my dxf prog is on another PC, but maybe a
printscreen in gif format would be a better way to "show it off"


martin

 

[John Fields]

I've used PCBExpress to design my first ever board (not quite accurate
- back in the sixties I played with copper clad boards and ferric
chloride solutions, but the results weren't great.)

Before I spend money on having this commercially cut, I'm hoping
someone will take pity on a relative newbie and point out any errors
and stupidities in the board layout. I'm not asking for circuit
analysis - just someone who has the time to look at how I laid the
traces, and point up obvious problems. I've never done two layer
before. It's been a lot of years since I did one layer.

Especially, there are a couple of points at which I have a component's
leg going through the board, and a trace connecting to it on both the
top and bottom layer. I'd like the top and bottom trace connected
whether or not the component is installed, but PCBExpress wasn't
totally clear on whether all holes for components are really cut as
vias. It makes sense that they would be, but I'd rather not find out
the hard way.

---
Specify "plated through holes" and the traces will be connected
where the hole pierces them.
---

Anyway, it's all connectors, DIPs, resistors and caps, and hopefully
not difficult for someone who does this for real to grok and comment
on. Many thanks in advance. I promise to learn from my mistakes.

www.obsessionaudio.com/dimmer2.pcb [if you have PCBExpress]
www.obsessionaudio.com/dimmer2.dxf [which I hope is readable - I
can't tell]

 

[petrus bitbyter]

I've used PCBExpress to design my first ever board (not quite accurate
- back in the sixties I played with copper clad boards and ferric
chloride solutions, but the results weren't great.)

Before I spend money on having this commercially cut, I'm hoping
someone will take pity on a relative newbie and point out any errors
and stupidities in the board layout. I'm not asking for circuit
analysis - just someone who has the time to look at how I laid the
traces, and point up obvious problems. I've never done two layer
before. It's been a lot of years since I did one layer.

Especially, there are a couple of points at which I have a component's
leg going through the board, and a trace connecting to it on both the
top and bottom layer. I'd like the top and bottom trace connected
whether or not the component is installed, but PCBExpress wasn't
totally clear on whether all holes for components are really cut as
vias. It makes sense that they would be, but I'd rather not find out
the hard way.

Anyway, it's all connectors, DIPs, resistors and caps, and hopefully
not difficult for someone who does this for real to grok and comment
on. Many thanks in advance. I promise to learn from my mistakes.

www.obsessionaudio.com/dimmer2.pcb [if you have PCBExpress]
www.obsessionaudio.com/dimmer2.dxf [which I hope is readable - I
can't tell]

Having a quick view, I saw no spectacular things. Some components/holes are
pretty close to the edge but if ExpressPCB (not PCBExpress) does not
complain why worry? Did you forget to draw mounting holes or do you have
another method to fasten the pcb?

petrus bitbyter

 

[linnix]

I've used PCBExpress to design my first ever board (not quite accurate
- back in the sixties I played with copper clad boards and ferric
chloride solutions, but the results weren't great.)

Before I spend money on having this commercially cut, I'm hoping
someone will take pity on a relative newbie and point out any errors
and stupidities in the board layout. I'm not asking for circuit
analysis - just someone who has the time to look at how I laid the
traces, and point up obvious problems. I've never done two layer
before. It's been a lot of years since I did one layer.

Especially, there are a couple of points at which I have a component's
leg going through the board, and a trace connecting to it on both the
top and bottom layer. I'd like the top and bottom trace connected
whether or not the component is installed, but PCBExpress wasn't
totally clear on whether all holes for components are really cut as
vias. It makes sense that they would be, but I'd rather not find out
the hard way.

Anyway, it's all connectors, DIPs, resistors and caps, and hopefully
not difficult for someone who does this for real to grok and comment
on. Many thanks in advance. I promise to learn from my mistakes.

www.obsessionaudio.com/dimmer2.pcb [if you have PCBExpress]
www.obsessionaudio.com/dimmer2.dxf [which I hope is readable - I
can't tell]

haven't had a look, since my dxf prog is on another PC, but maybe a
printscreen in gif format would be a better way to "show it off"

I vote for a jpg "screen capture" and gerber files for details.
I can't read .pcb or .dxf.

 

[Spehro Pefhany]

I vote for a jpg "screen capture" and gerber files for details.
I can't read .pcb or .dxf.

..gif (or png) is better for that kind of screen capture.


Best regards,
Spehro Pefhany

 

[ScottM]

http://www.obsessionaudio.com/dimmer2.jpg

Red is top, green is bottom, board size is 3.8x2.5". Especially comment
on what I'm letting myself in for in terms of soldering effort. It
occurs to me that soldering points 0.1" apart is going to be difficult;
is there a clever way to do this?

ExpressPCB did let me get the board laid out fairly quickly, and
without solder mask and silkscreen I can get this done for $51. What's
cheaper and better? I will need 2-3 custom boards, and if things go
well, a number of copies of each down the road.

 

[Spehro Pefhany]

http://www.obsessionaudio.com/dimmer2.jpg

The power connections to the (obsolete) LM3900 appear to be reversed.
You should probably have some bypass capacitors across the 5V & 12V
supplies. I didn't attempt to understand all that you're doing-- but
running CMOS input pins off the board directly is often not wise.

Checking hole sizes and noting clearances on each footprint/padstack
is often not a waste of time.

Red is top, green is bottom, board size is 3.8x2.5". Especially comment
on what I'm letting myself in for in terms of soldering effort. It
occurs to me that soldering points 0.1" apart is going to be difficult;
is there a clever way to do this?

No, just spend the 10 minutes and do it perfectly the first time,
d*mmit.

ExpressPCB did let me get the board laid out fairly quickly, and
without solder mask and silkscreen I can get this done for $51. What's
cheaper and better? I will need 2-3 custom boards, and if things go
well, a number of copies of each down the road.

Best regards,
Spehro Pefhany

 

[Homer.Simpson]

ScottM said

I've used PCBExpress to design my first ever board (not quite

ExpressPCB is great, IMHO.

Before I spend money on having this commercially cut, I'm hoping
someone will take pity on a relative newbie and point out any
errors and stupidities in the board layout.

I'd alter the ~90deg bends to two ~45deg bends. See LM3900 pin 4 as
an example.

I'd like the top and
bottom trace connected whether or not the component is installed,
but PCBExpress wasn't totally clear on whether all holes for
components are really cut as vias.

Component pads will connect the top/bottom layers even without the
component installed.

Since you are ordering MiniBoard's you won't get the silkscreen. I'd
recommend lowering the text "Spot", "Exit", "Beep", etc to the top
(red) layer. Ditto for any other text you'd find useful.

Later

 

[Winfield Hill]

ScottM wrote...

It occurs to me that soldering points 0.1" apart is going
to be difficult ...

No, you'll find that's easy, we've all been doing it for
more than 50 years. It's 0.05" that begins to show real
issues, and 0.5mm (about 0.020") that raises your eyebrows.
After that you can go for the really-miniature stuff.

 

[linnix]

The power connections to the (obsolete) LM3900 appear to be reversed.

Yes, unless the chip is mounted upside down, but then some other wires
might be wrong.

You should probably have some bypass capacitors across the 5V & 12V
supplies. I didn't attempt to understand all that you're doing-- but
running CMOS input pins off the board directly is often not wise.

Checking hole sizes and noting clearances on each footprint/padstack
is often not a waste of time.

I would use bigger holes/pads, especially if you need to rework
without damaging the parts/board.

No kidding, we sometime have to do 0.5mm (0.02").

 

[David L. Jones]

http://www.obsessionaudio.com/dimmer2.jpg

Red is top, green is bottom, board size is 3.8x2.5". Especially comment
on what I'm letting myself in for in terms of soldering effort. It
occurs to me that soldering points 0.1" apart is going to be difficult;
is there a clever way to do this?

ExpressPCB did let me get the board laid out fairly quickly, and
without solder mask and silkscreen I can get this done for $51. What's
cheaper and better? I will need 2-3 custom boards, and if things go
well, a number of copies of each down the road.

General comments from a quick glance...
- Take out the right angles
- Use only 45deg angles (like the Exit & Beep tracks)
- I can't see why you need a double sided board for this, it could be
done single sided with a few links at most.
- The pads are a bit small, make them bigger and oval shaped.
- You've put tracks on the top when you could have put them on the
bottom. The top connector for example, the tracks should all be on the
bottom, and only needed ones on the top.

Note these these are really just esthetics. Electrically I can't
comment at a quick glance.

My PCB Turtorial might help:
http://alternatezone.com/electronics/pcbdesign.htm

Other than that, not a bad first effort.

Regards
Dave

 

[James Thompson]

I've used PCBExpress to design my first ever board (not quite accurate
- back in the sixties I played with copper clad boards and ferric
chloride solutions, but the results weren't great.)

Before I spend money on having this commercially cut, I'm hoping
someone will take pity on a relative newbie and point out any errors
and stupidities in the board layout. I'm not asking for circuit
analysis - just someone who has the time to look at how I laid the
traces, and point up obvious problems. I've never done two layer
before. It's been a lot of years since I did one layer.

Especially, there are a couple of points at which I have a component's
leg going through the board, and a trace connecting to it on both the
top and bottom layer. I'd like the top and bottom trace connected
whether or not the component is installed, but PCBExpress wasn't
totally clear on whether all holes for components are really cut as
vias. It makes sense that they would be, but I'd rather not find out
the hard way.

Anyway, it's all connectors, DIPs, resistors and caps, and hopefully
not difficult for someone who does this for real to grok and comment
on. Many thanks in advance. I promise to learn from my mistakes.

www.obsessionaudio.com/dimmer2.pcb [if you have PCBExpress]
www.obsessionaudio.com/dimmer2.dxf [which I hope is readable - I
can't tell]

If you would include your .sch we could tweak it for you. Also this is such
a simple board, you can do this yourself. save a bundle.. If you want to
explore a simple method, go to teknics web site and order the press-n-peel
blue toner transfer sheets. Makes it simple to make prototype simple boards.
I believe on your board you have a gnd and supply tied together also on the
right side of the board.
Jtt...

 

[Deefoo]

I've used PCBExpress to design my first ever board (not quite accurate
- back in the sixties I played with copper clad boards and ferric
chloride solutions, but the results weren't great.)

Before I spend money on having this commercially cut, I'm hoping
someone will take pity on a relative newbie and point out any errors
and stupidities in the board layout. I'm not asking for circuit
analysis - just someone who has the time to look at how I laid the
traces, and point up obvious problems. I've never done two layer
before. It's been a lot of years since I did one layer.

Especially, there are a couple of points at which I have a component's
leg going through the board, and a trace connecting to it on both the
top and bottom layer. I'd like the top and bottom trace connected
whether or not the component is installed, but PCBExpress wasn't
totally clear on whether all holes for components are really cut as
vias. It makes sense that they would be, but I'd rather not find out
the hard way.

Anyway, it's all connectors, DIPs, resistors and caps, and hopefully
not difficult for someone who does this for real to grok and comment
on. Many thanks in advance. I promise to learn from my mistakes.

www.obsessionaudio.com/dimmer2.pcb [if you have PCBExpress]
www.obsessionaudio.com/dimmer2.dxf [which I hope is readable - I
can't tell]

Make it single sided.

--DF

 

[ScottM]

If you would include your .sch we could tweak it for you.

I've posted a .bmp to www/obsessionaudio.com/dimmer2.bmp - I don't
promise it's lovely. The .sch tool and I had some disagreements.

The idea is to get output from PWM generators (9 of them) and use them
as follows:

3 are generating (varying) audio frequencies. I want to combine these
(using XOR, for simplicity) into a single signal, bump up the voltage
(ULN2003A), and put it across a small cap to grind off the square
edges. Then it can go into a speaker or a small amp. I realise that
XORing square waves doesn't exactly preserve the frequencies, but
that's ok. I just need a rich source of different, simple sounds.
(Usually, some or all all PWMs are turned off).

4 are generating output (probably at around 400kHz) for a commercial
dimmer. I want to end up with 4 lines, each adjustable to 0 to +10v
output, based on duty cycle. (The dimmer demands 4 lines varying
between 0 to +10v and a common ground.)

I didn't know of a simpler way to boost the square wave from off/on to
0/+10v, so I'm using a norton op amp with a 12v input, and then a
voltage divider to get the output down to 0-10v, and then a cap to
smooth out the waveform. I have something like this running on a
breadboard and it works reasonably well. But I don't like using an op
amp for this, because it means extra resistors, to pull up the (-) leg.
And the part is apparently obsolete now. Can I safely use some simpler
device for this? What's the right way?

2 are generating output for an array of LEDs, which I want to "dim by
brute force". But since the LEDs are common anode, I can use a ULN2003
to amplify the square wave, and just put it through a resistor and
across a cap to get a little smoothing and current control.

All the PWM is coming off a PC104 card and the available current is
typically 2ma on each output pin. I worry about drawing too much
current and blowing a $200 card. I also worry about radiating noise by
sending a 400kHz square wave over a ribbon cable. And I wonder if (as
someone mentioned) bringing signals over from another board is just
going to create a lot of noise problems.


So, some questions:

1) Is there a better way to do this. My design skills... well, I'm a
software guy. My code looks gorgeous. I doubt those circuits look as
good.

2) Several people have recommended avoiding right angles in traces.
Because they fail? Because they are ugly? Because electrons don't
corner well?

I've noted the advice about going single layer, and I'm thinking about
it. I don't want to do my own boards though - I don't have a drill
press and I really do want to mount through holes, given my soldering
skills. Speaking of which, what's a good soldering iron? My "radio
Shack special" has too blunt a tip to get into 0.1" places, and the
fancy "Cold heat" portable I got is a pain to use.

Many thanks to all those kicking in suggestions.

 

[ScottM]

OK, the LM3900 looks like a bad idea. Would this work instead?

TC4468:
http://rocky.digikey.com/WebLib/Telcom/Web Data/TC4467,68,69.pdf

All I want to do is take the output of a PWM (which has very little
current available) and raise it up to 0-12v; it looks like this chip
will handle up to 16V, and from the looks of things, only draws 10uA,
so connecting it directly to a source-2ma-at-most pin ought to be very
safe, yes?

 

[linnix]

I've posted a .bmp to www/obsessionaudio.com/dimmer2.bmp - I don't
promise it's lovely. The .sch tool and I had some disagreements.

The idea is to get output from PWM generators (9 of them) and use them
as follows:

3 are generating (varying) audio frequencies. I want to combine these
(using XOR, for simplicity) into a single signal, bump up the voltage
(ULN2003A), and put it across a small cap to grind off the square
edges. Then it can go into a speaker or a small amp. I realise that
XORing square waves doesn't exactly preserve the frequencies, but
that's ok. I just need a rich source of different, simple sounds.
(Usually, some or all all PWMs are turned off).

How about an op amp summing junction? It would be cheaper and easier,
just resistors.

4 are generating output (probably at around 400kHz) for a commercial
dimmer. I want to end up with 4 lines, each adjustable to 0 to +10v
output, based on duty cycle. (The dimmer demands 4 lines varying
between 0 to +10v and a common ground.)

I didn't know of a simpler way to boost the square wave from off/on to
0/+10v, so I'm using a norton op amp with a 12v input, and then a
voltage divider to get the output down to 0-10v, and then a cap to
smooth out the waveform. I have something like this running on a
breadboard and it works reasonably well. But I don't like using an op
amp for this, because it means extra resistors, to pull up the (-) leg.
And the part is apparently obsolete now. Can I safely use some simpler
device for this? What's the right way?

How about MOSFET or darlington?

2 are generating output for an array of LEDs, which I want to "dim by
brute force". But since the LEDs are common anode, I can use a ULN2003
to amplify the square wave, and just put it through a resistor and
across a cap to get a little smoothing and current control.

All the PWM is coming off a PC104 card and the available current is
typically 2ma on each output pin. I worry about drawing too much
current and blowing a $200 card. I also worry about radiating noise by
sending a 400kHz square wave over a ribbon cable. And I wonder if (as
someone mentioned) bringing signals over from another board is just
going to create a lot of noise problems.

I would have to look at your PC104 output stage.

So, some questions:

1) Is there a better way to do this. My design skills... well, I'm a
software guy. My code looks gorgeous. I doubt those circuits look as
good.

Not if you are making thousands of them.

2) Several people have recommended avoiding right angles in traces.
Because they fail? Because they are ugly? Because electrons don't
corner well?

Because they are discontinuity to high frequence signals, i.e. antenna.

I've noted the advice about going single layer, and I'm thinking about
it. I don't want to do my own boards though - I don't have a drill
press and I really do want to mount through holes, given my soldering
skills. Speaking of which, what's a good soldering iron? My "radio
Shack special" has too blunt a tip to get into 0.1" places, and the
fancy "Cold heat" portable I got is a pain to use.

I would put components on both sides, using 0805 SMD parts. The board
can fit in perhaps 1/4 of your exisiting design.

 

[ScottM]

I can't imagine hand-soldering SMD components. I always assumed special
machines were used to mount that stuff...

 

[Rich Grise]

http://www.obsessionaudio.com/dimmer2.jpg

Red is top, green is bottom, board size is 3.8x2.5". Especially comment on
what I'm letting myself in for in terms of soldering effort. It occurs to
me that soldering points 0.1" apart is going to be difficult; is there a
clever way to do this?

ExpressPCB did let me get the board laid out fairly quickly, and without
solder mask and silkscreen I can get this done for $51. What's cheaper and
better? I will need 2-3 custom boards, and if things go well, a number of
copies of each down the road.

OK, you did ask, so here goes! ;-)

Looks good, except I'd double the power and ground traces - put +V on
the top, and put them opposite each other, and go all the way around the
perimeter of the board, plus - well, heck - just fill up the whole
rest of the top of the board with ground plane. (wherever there isn't
circuitry, of course! ;-) )

Assuming it's still just data, that shouldn't take long at all.

Good Luck!
Rich

 

[DJ Delorie]

I can't imagine hand-soldering SMD components. I always assumed special
machines were used to mount that stuff...

Hand-soldering larger SMD parts is *easy*. In fact, somewhat easier
than through-hole parts. To solder an 0805 resistor, for example:

Pre-tin one of the pads with a little solder.

Put 0805 part in the right place over the pads, hold down with
something pointy (I use pointy tweezers, you could use a toothpick).

Touch the pre-tinned pad to melt the solder. Make sure you're pushing
down (lightly) on the part at this point; it will settle onto the pad
as soon as the solder melts, but it's really easy to move it around
with the surface tension of the solder at this point. Pressing down
on it makes it stay in place.

Solder the other pad.

You can use this technique for parts with a small number of pins. For
larger parts (SOJ or QFP), you tack down opposite corners using the
pre-tin method, then drag a blob of solder across the pins to solder
them all down quickly. A little desoldering braid cleans up any
shorts, if any.