Advise requested on complex PCB layouts - Can't get it with ExpressPCB

T&E Engineer · 2009-10-11 14:41

I am working on a new design of 6 RGB LED matrixes interfaced to 3 HT1632C LED drivers (52 pin QFP). Each of the HT1632C chips have 24 cathode outputs (columns) and 16 anode outputs (rows). Basically it will be an expanded version of the SURE Electronics 2416 board: http://www.sureelectronics.net/goods.php?id=142 but this will require 3 chips for red, green and blue.

I started using ExpressPCB (which I have used many times before) with designing the RGB LED matrix displays first and then designing a 52 pin QFP layout to the design specs of each. I then layed out the RGB LED matrixes how I want them and started to connect them in ExpressPCB. I brought all the connections out and then it was time to lay down the 3 HT1632C chips.

The problem is that "each" of the 3 chips has 24+16 connections to the 6 RGB LED matrixes. I can't seem to get it right in the layout to make it work. I am constantly having to add through holes to connect the top / bottom layers and I don't think I will be able to get it layed out right.

My other option is to hand wire it on a perf board - which I may have to do. However, I would really like a PCB layout so I can expand it later and make it bigger. I spent many hours yesterday just with ExpressPCB to see that it may not work for me.

Is there any other PCB software that is free preferably that can automatically draw the PCB if I was to use it's schematic portion first to lay it out in a drawing? I don't beleive ExpressPCB can do this with nodes but not sure.

Any ideas on how to handle this complex mess - or should I just make a perf board with hand wiring (30 guage wire). I have also attached my started ExpressPCB layout too.

Thanks for your help!

mctrivia · 2009-10-11 15:44

eagle and most other software have the ability to auto route but i have never had much luck with any of them working and just wrote all by hand.

don't be afraid to run traces on both sides. you may have to use tighter width/clearance values to get what you need done. how far apart are you trying to keep your traces? can you run them closer together and get it to work?

try using surface mount parts when ever reasonable. don't be afraid of them many are easy to solder and they will make routing easier because they take up no space on the other side of the board.

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T&E Engineer · 2009-10-11 15:56

I am using both sides with via holes to connect. I am also running a tight as I can as seen by the PCB file I attached before. There are just alot of traces in very tight areas to work around. I haven't even considered surface mount parts yet which will most likely happen. I am just concerned at all of the row and columns going to 3 QFP chips.

I hate having to go to a perf board if multiple boards "may" be made in the future but I was hoping to hear about an automatic routing solution. I also tried the linking feature in ExpressPCB and ExpressSCH and all it did was highlight which pads needed to be connected. Well that's not hard but somewhat convinient - but it makes you have to create a schematic first also. Ugh.

Other ideas - anyone?

mctrivia · 2009-10-11 17:38

There is always an option. My current board uses 4mil clearance and 4 mil spacing with 8 mil via to handle the 200 traces going to a 256mbga ic.

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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

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T&E Engineer · 2009-10-11 18:22

Yea thats true. I just rethought the layout and was able to move the "Green" LED handled HT1632C closer to the top left RGB display which allowed me to connect ALL the connections. 1/3 the way done now. Now where to place the "Red" and "Blue" LED handled HT1632 chips.

Thanks again.

Searider · 2009-10-12 18:07

Have you looked at DipTrace. It is a great pro/simi-pro intigrated Schematic and PCB layout suite with Autoroute. I have used the autoroute feature but have done several PCBs starting with the Schematic.

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Searider

T&E Engineer · 2009-10-12 18:16

I actually download DipTrace last night and also uninstalled it later after reading some other forum posts on the subject (not parallax forum) about that PCB designers almost always do it by hand and can not trust the autorouting capabilites of·the big name·PCB software. It was after reading that, when I decided to rethink another layout and currently now have 2 of the 3 chips placed and wired using ExpressPCB. Tonight I will figure out where to place the last chip and run the traces.

Thanks.

mctrivia · 2009-10-12 19:42

Problem with express pcb is you will pay a fortune to get boards made since you can only get from them

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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

WBA Consulting · 2009-10-12 21:55

I use DipTrace and don't have any trouble with autorouting per schematic. The posts you mention are more than likely related to people looking for a quick-fix, out-of-the-box PCB software. But, as with any autorouter, you need to set it up properly for your design needs. Most people try to use the default autorouter setup in DipTrace and then complain when it doesn't work to their satisfaction. I was one until I took the time to make some adjustments in the autorouter setup. It works great now. My only issue left is that sometimes I want traces routed differently for cosmetic appearance reasons, so I do some smaller designs by hand.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010

T&E Engineer · 2009-10-13 18:50

I went to calculate the cost of my board for (2) and it was $128 (or $64 each). Even if I bought 100, it would still be over $32 each using ExpressPCB. Sure Electronics sells a smaller board with all components (for just RED LED Matrix not RGB like mine) for about $12. How can they do this as the price of the PCB would have to be under $1 or so?

I'm too the point right now that I forgot to add in the 24 * 3 resistors in surface mount (or 1/8W regular) that I will have to redesign the board again to make everything fit OR just hand wire it on a perf board.

Am I really just going about this the wrong way.

Comments...Thoughts?

mctrivia · 2009-10-13 18:54

For 2 layer boards I usually pay about $1 each including shiping. I keep the boards small and get 100 or so made at a time in china.

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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

T&E Engineer · 2009-10-13 18:57

OK Great. Can you share your source or PM me? I'm thinking about giving Eagle a try also. I've only really used ExpressSCH and ExpressPCB so it will be a learning curve.

mctrivia · 2009-10-13 19:01

Gold phoenix

$110 for 155 sq inch

I pay extra for silver coat and testing. Silver or gold coat is only needed if you want to be rohs compliant.

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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.