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Help with PCB creation


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http://i66.tinypic.com/34r6ko3.jpg

 

I want to have a small run of PCB's produced and would appreciate some guidance.

 

Looking at using pcbway for the production.

 

Using FreePCB software.

 

Have 6 gerber files plus drill file prepared.

 

Wondering if my layout pictured above is okay?

 

Not sure if the trace from the R1 pad going to the 2nd top left pin on the 14 pin socket is acceptable?

 

Basically trying to create a small PCB with a 14 pin socket to house a 14 pin PIC, with traces going to various holes where I can add some single pin headers or wires with a couple of resistors in the mix.

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Looks good - I would make each leg coming from the termination pads much thicker so they don't potentially crack at the pad.

 

How about mounting holes?

 

You should also add a small cap across the power rails as close as possible to the chip. Maybe a 0.01 or 0.1uf

 

Also pin4 (master clear) should either be tied high or take it high with a resistor (47K?)

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Don't striclty need mounting holes but thanks for the reminder.

 

I've imported it into KiCad as it has a nice 3D viewer and it looks good. Will do a small run and tweak from there.

 

This is all very new to me but I'm eager to learn.

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Looks good - I would make each leg coming from the termination pads much thicker so they don't potentially crack at the pad.

 

How about mounting holes?

 

You should also add a small cap across the power rails as close as possible to the chip. Maybe a 0.01 or 0.1uf

 

Also pin4 (master clear) should either be tied high or take it high with a resistor (47K?)

 

 

It is recommended to tie MCLR pin4 high with a 1K or higher resistor. and its recommended to use a 0.1uf cap across VDD and VSS as close as possible to the PIC.

 

- - - Updated - - -

 

don't forget the pin 4 or the PIC won't run.

 

Not entirely true. You can enable the MCLRE bit which ties MCLR to VDD internally.

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Not real familiar with PIC pinouts so I will ask the question.

 

This IS the reverse image as in the solder side, isn't it?.

 

Wouldn't be the first time someone has drawn out a PC artwork and it is the reverse of what they want.

 

The layout looks nice to me, I hate unnecessary links when simple re-orientation of parts can remove them and it looks like you have done that.

 

Simple things like leaving enough spacing between the resistor holes so it can sit neatly, IC pin spacing so it actually suits the IC and socket.

 

If you are attaching to the board with connectors, why not use just one connector and certainly don't use individual connectors that require individual markings.

 

I much agree with Mike though, you should allow for PC board mount holes even when you don't think you may need them.

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Not real familiar with PIC pinouts so I will ask the question.

 

This IS the reverse image as in the solder side, isn't it?.

 

Wouldn't be the first time someone has drawn out a PC artwork and it is the reverse of what they want.

 

The layout looks nice to me, I hate unnecessary links when simple re-orientation of parts can remove them and it looks like you have done that.

 

Simple things like leaving enough spacing between the resistor holes so it can sit neatly, IC pin spacing so it actually suits the IC and socket.

 

If you are attaching to the board with connectors, why not use just one connector and certainly don't use individual connectors that require individual markings.

 

I much agree with Mike though, you should allow for PC board mount holes even when you don't think you may need them.

 

All PCB programs draw the layout as if you are looking down on the board from the top - the parts side.

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Top of board:

 

http://i64.tinypic.com/2ykcoxc.jpg

 

Bottom of board:

 

http://i66.tinypic.com/jshd3m.jpg

 

So silk screen on top, traces on bottom.

 

I plan on soldering in the socket, resistors and headers myself, inserting from top and soldering to bottom.

 

I used single headers to allow for more room. Also couldn't find a single row 7 pin header in the parts list of the FreePCB software. As mentioned I'm still very new to this.

 

I've already prototyped and tested the board with stripboard from Jaycar.

 

http://i67.tinypic.com/ixfeo4.jpg

 

http://i68.tinypic.com/2ywydm9.jpg

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FreePCB is the absolute easiest program to draw new footprints with. I do it almost daily.

 

You have chosen an absolutely fantastic program with very few bugs and only two (for me) negatives.

 

It doesn't allow components to be placed at angles and you can't draw curved board outlines. For that we use Altium but it is hugely painful to use.

 

One comment about making boards - it is usually no different price wise to make a board double sided with plated through holes than a single sided board.

 

A bonus is that plated through holes create a much stronger board (electronically).

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All PCB programs draw the layout as if you are looking down on the board from the top - the parts side.

 

Ow that is just cheating. I must be showing my age doing all this stuff by hand aye.

 

Still, I do get great satisfaction making my own boards except when I need multiples of the same board.

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Thanks Mike, I stumbled across FreePCB from a suggestion of yours to another member on a different forum post.

 

I find importing into KiCad is handy for me to better visualise the finished product. The renders above are from the KiCad 3D viewer.

 

Have sent the 6 gerber files plus drill file to pcbway, will see what happens next.

 

- - - Updated - - -

 

http://i65.tinypic.com/qyh0nc.jpg

 

http://i66.tinypic.com/33p4wuw.jpg

 

For reference, the files that were sent and specs of the order.

 

I'll update here if/when I receive a final product.

 

It's for switchless region changing of a Sega Master System console. Holding down the reset button cycles through 50/60Hz and changes the power LED colour from green to blue to indicate mode.

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The capacitor is there in case of ripples on the +5 line I would think. You don't need a very powerful capacitor for the job, but it can prevent issues down the line caused by not having a clean +5 signal.
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The capacitor is indeed a highly recommended part of the design. Without it you may get unreliable operation.

 

Its job is to lower the effective impedance of the 5V supply for the micro. The tracks and wires from the 5V supply are thin and can quite high impedance (AC resistance) at higher frequencies.

 

TLDR version; You should have it because ... electronics reasons.

 

As Mike said, you should also use thicker traces, especially going to the connector pads.

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Cheers guys, learning heaps.

 

I was just using the software's default trace size so appreciate the advice re using thicker lines.

 

Re power, so I can just bridge a cap across pins 1 and 14 which are the PIC's ground and voltage pins?

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You could tack the capacitor right onto the PIC, but it's not critical for your application. Just add the capacitor footprint to the board up that end of the PIC.

 

Ideally the 0V and 5V traces should go to the capacitor's pads, then continue on to the respective IC pads.

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If you look at any arcade game board from the past chockka with chips you will see (usually) a 0.1uf cap - often a disc ceramic but that's not important, across the power rails at EVERY chip on the board.

 

I.C.s draw a huge current on output switching but for a microscopic time. This cap enables the chip to suck as much current as it needs for that tiny instant. That's a simplistic description as there is a LOT more to it - if you have a half hour to spare watch this: (I learned a few tips from this guy)

 

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http://i66.tinypic.com/15pqpme.jpg

 

So I've widened the traces to 25 mils and incorporated the power cap. Am I on the right track?

 

Not sure what I've done wrong but I now get a design rule error, stating that the cap negative pad is 0mm.

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The footprint used is for a radial electro cap, where as a bypass or ceramic type is more appropriate.

 

Change the track coming out of the cap +ve so that it at right angles to the one coming in.

 

You can also move the other tracks away from each other a bit. You have plenty of room.

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