Need second or 3rd set of eyes

[MrDEB]

I have a scheamatic and a pc board layout done in PCB123 files.
Am I asking too much for someone to ponder over?
may need to add a 1M resistor to 4030 input.
don't think I can upload PCB123 files??
any suggestions or Email direct?

 

[Optikon]

I have a scheamatic and a pc board layout done in PCB123 files.
Am I asking too much for someone to ponder over?
may need to add a 1M resistor to 4030 input.
don't think I can upload PCB123 files??
any suggestions or Email direct?

Can you make standard graphic images of the files? i.e. *.gif, *.png, *.jpg so that others can see? Heck, you can probably even save a screenshot and it would work well enough. Alot of people on here would be glad to see what you're up to and offer some advise if you need it. A schematic and a description of how it is supposed to operate would help alot also.

 

[MrDEB]

here are 2 pics, one of schamatic abnd other is circuit board copper traces
this is a starting tree for "pinewood derby dragracing"
it has 1 blue light, 3 yellow lights, 1 red light and one green light.
Relays 2 and 3 control the red lights-only first one on before the green light comes on.
the relays 1 & 4 control the 24 v solenoids and turns on the red light if enabled with the output from the 4030 (H + H = L which turns on the 2n3906
the diodes D1-D4 are ORed from output from the 4017 decade timmer configured as a count to N and stop.
circuit works but would like to clean up proto type - wires running rampant, cut wires, etc. a real mess.
present circuit is on 3 seperate boards.
the circuit diagram is a 5 x 5 board
J1-pcb = lights
J2-pcb = solenoids
J4-3 = driver control pushbuttons
J4 = enavles the 555 timer output to start counting


URL=http://i59.photobucket.com/albums/g291/Doug-in-the-woods/schamatic.gif]**broken link removed**[/URL]
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[MrDEB]

Oups got something screwed up
heres the right urls

**broken link removed**
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[TrevorP]

The PCB seems really spread out to me...like it seems like you could make it a lot smaller.

 

[Kingpin094]

Are you planning to have this board made or make it yourself?

Looks a lot like ExpressPCB software to me but maybe they are the same.

I would agree with TrevorP as the board seems really spread out. Just from personal experience it always helps to make the traces look nice as that usually helps to find errors.

 

[Optikon]

Have you simulated any of this logic? It could be helpful since it looks evry time consuming to study. Why so many jumpers and open circuit configurations? I dont know what all will be installed so I cannot say for sure that this circuit will work at all.

 

[ericgibbs]

I have a scheamatic and a pc board layout done in PCB123 files.
Am I asking too much for someone to ponder over?
may need to add a 1M resistor to 4030 input.
don't think I can upload PCB123 files??
any suggestions or Email direct?

hi,
Looking over the cct diagram, as you have R6, a 200K tied to 0V from the only used input pin of the 4030 I cannot see any reason for a 1M0 .

The gate is driven by the 4 diodes, wired as an OR from the 4017.

On the drawing I dont see any decoupling?

The quality of the artwork print is so poor its almost impossible to read it.

 

[MrDEB]

art work quality and spread out board

this is my first attempt at designing and etching a pc board. Reason why its spread out - just camo out like that. the board is 5x5 what with the relays??
on resistor R6 it was mentioned on this form that I have a floating input to the 4030.
circuit works and looked at schamatic several times and see that maybe it isn't floating.The output from the ORed diodes keeps the input (4030) tied low until a green light comes on then the input goes high .
Decoupling non existence. perhaps I need some??
I know ttl needs it but does cmos??
the schamatic does work, I have a working unit. Just want to make it look better what with all the cut wires etc.
As for all the jumpers, this is my first board designed from scratch. Yes I hope to etch it myself.

 

[ericgibbs]

this is my first attempt at designing and etching a pc board. Reason why its spread out - just camo out like that. the board is 5x5 what with the relays??
As you get more experience you will be able to optimise your layouts.

on resistor R6 it was mentioned on this form that I have a floating input to the 4030.
circuit works and looked at schamatic several times and see that maybe it isn't floating.The output from the ORed diodes keeps the input (4030) tied low until a green light comes on then the input goes high .

I can clearly see on your drawing R6,200K from the 4030 input pin to ground.

Decoupling non existence. perhaps I need some??
I know ttl needs it but does cmos??

Decoupling is essential for all logic devices, at least one 0.1uF/chip, also a 10uF on the power line.
the schamatic does work, I have a working unit.
It most likely will work, but without decoupling it could behave erratically.

Just want to make it look better what with all the cut wires etc.
As for all the jumpers, this is my first board designed from scratch. Yes I hope to etch it myself.

I hope all goes to plan.

 

[Optikon]

this is my first attempt at designing and etching a pc board. Reason why its spread out - just camo out like that. the board is 5x5 what with the relays??
on resistor R6 it was mentioned on this form that I have a floating input to the 4030.
circuit works and looked at schamatic several times and see that maybe it isn't floating.The output from the ORed diodes keeps the input (4030) tied low until a green light comes on then the input goes high .
Decoupling non existence. perhaps I need some??
I know ttl needs it but does cmos??
the schamatic does work, I have a working unit. Just want to make it look better what with all the cut wires etc.
As for all the jumpers, this is my first board designed from scratch. Yes I hope to etch it myself.

My initital impression was that I don't see anything grossly worng with it.. (like others have said, tough to trace through)

If you made only one of these boards for a one-off project then you probably don't need to add any decoupling.. however, as a general rule, for logic that contains transistors that switch states very fast (CMOS included!) you should provide local decoupling to the device. This will help eliminate potential parasitic oscillations (HF), ground bounce etc..

 

[MrDEB]

where to add caps

will add some caps .1uf between power and ground
have 2 caps between power and ground now.

 

[MrDEB]

How can one design a board that is easier to trace?
any rules or guidlines.
I want to learn by doing.

 

[ericgibbs]

How can one design a board that is easier to trace?
any rules or guidlines.
I want to learn by doing.

hi,

You have heard it before, good artworking is down to practice.

As the designer of the electronic part of your circuit you should have a mental image on how the finished pcb should look.

For instance, you have an idea what the finished size and shape of the pcb, sometimes you will not have a free choice,
if you are designing a pcb to fit an existing enclosure.

Points to consider when doing an artwork layout are:-

- the voltage on the tracks will determine the minimum spacing between tracks.

- the current carried by a track will determine is minimum width.

- a track, carrying a low level signal or a heavy noisy signal will require careful routing.

- a heat generating component will need clearance away from heat susceptable components.

- a heavy component fixed to a pcb may require fixing holes or large copper pads.

- the decoupling components should be considered as part of the circuit/artwork layout.

- ensure that the pad size, when its got the correct size holed drilled thru, has enough
copper remaining to enable a quality solder joint.

- some designers [I do] work on a X/Y layout, that is tracks on the back of the pcb, horizontal.
tracks on the front of the pcb vertical. [where possible]

- allow space and track for off board connections.

- don't forget the pcb mounting holes, at the corners and one in the middle, if its a big board.

- large blank areas of your pcb, can be used for dummy track/pads for later mods, or tracked over.
this will reduce your etchant usage, no point in etching copper from these areas.

- if possible, use pad/tracks for Test Points, identify them with lettering.

No two designers will layout an artwork the same way.

These a just a few points, there are lots more!.

Get a good artworking program, practice on 'dummy' layouts, create lots of component outlines,
prove them and use them as building bricks for your layouts.

SAVE you work on a regular basis, before you make an important change, SAVE the current artwork file,
rename the artwork and then modify the artwork, this way, if you screw up, you have not wasted all of your work.


Just a few links, bit deep, but you have to know some of the standards.


**broken link removed**

http://www.new-wave-concepts.com/files/PWtutor4.pdf

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[Optikon]

How can one design a board that is easier to trace?
any rules or guidlines.
I want to learn by doing.

Some things that help when drawing schematics:

1) Draw them left to right according to signal flow. Put power supply things off in their own area so as not to "mix" them into rest of circuit.

2) Give lots of room and provide node labels so that one doesnt have to follow a wire that zig-zags all over the place. If it looks like a tangled mess - it is not done right.

3) Try to draw circuits in such a way that showing what they are doing is evident. I.e. if some logic circuit operates relays then place the logic near the relays and make it clear which relays they drive. Anotehr example is drawing amplifiers in a way that clearly shows feedback or stages so that it is easy for someone to calculate gain etc..

These are just some ideas. Drawing easily understandable schematics is somewhat of an art. The biggest mistake I see people make is trying to fit their whole design on one page. There is no reason for that especially these days where you can make an electronic copy to avoid paper waste. use lots of space when doings schematics. I prefer a 4 page schematic with each page only half full over a one pager with everything crammed into it anyday.

 

[MrDEB]

WOW lots of good info
will play with redesigning pcb
thanks
I think my pwer traces are tooo wide.
using 2 oz copper clad boards. .050 seems kinda wide for power traces?
whole board with the lights hooked up only draws a max of 275ma. (using automotive clearance lights for the yellow lights). the red, blue and green are RS lights only draw 90ma each(have connected in parrell)

 

[ericgibbs]

WOW lots of good info
will play with redesigning pcb
thanks
I think my pwer traces are tooo wide.
using 2 oz copper clad boards. .050 seems kinda wide for power traces?
whole board with the lights hooked up only draws a max of 275ma. (using automotive clearance lights for the yellow lights). the red, blue and green are RS lights only draw 90ma each(have connected in parrell)

hi,
Its good idea to keep your power tracks [+5V/0V] as wide as practical, 0.05" or 0.1" if you have the space and as direct as possible.
A wider power track has a lower impedance, this is desirable in a layout.

Remember to position your 0.1uF caps as close as possible to the ic's.

At point to note, is if you are using tungsten filament lamps [automotive] is that the resistance of the lamp when 'cold'
is about 10% of the 'hot' value.

So the initial 'warm up' current can be upto 10 greater, for a few ten's of millisecs, than the steady running current.
These current pulses can pull the power rails down, which can cause mis-operation of the circuitry, due to electrical noise.

So to minimise this, your psu must be capable of dealing with these current pulses.
One way, is a large value capacitor on the output of the psu, 4700uF or so.

 

[mneary]

Wide ground and power traces also makes the board easier to trace. Sort of self-labeling.