PCB cost vs protoboard wiring

T&E Engineer

I started designing a PCB using ExpressPCB for my 16x16 Matrix LED (4 - 8x8 LED modules) with a few driver chips.

I saw that the cost was going to be over $100 for just 2 boards!!

I understand that there is a lot of work that goes into making them. Trust me I spent all day yesterday just working on the design layout (which is still going to need a few jumper wires).

I decided to buy one of the etching kits from Radio Shack and do it myself. However, they give you a thick sharpie pen and 2 doublesided boards. After spending a few hours drawing very fine lines and drilling holes, I found out that the board·was too small and I needed to use a larger one. I also had to use a smaller drill bit than the 1/8" provided (1/16" I think but it was even a bit big) AND a thin sharpie pen.

Is this the right approach to take?

It would be easier to just use a protoboard but then there is a "rats nest" in wires. What do hobbiest do? I have already developed this on 4-5 Radio Shack solderless breadboards (as you can see this is getting expensive at $15 a board). I have already dumped over $200 into this "project". The solderless breadboards are nice but I have to use more of them because the (4) 8x8 LED modules don't line up well.

What are your thoughts on how to handle this problem on a small quantity of maybe 2-3?

I have already purchased 1/8" smoked plexiglass (to cover the 16x16 LED display) but this seems to be a bit thick - but may be ok. I also have pushbuttons and a·Radio Shack case too.

Thanks.

stamptrol

No question that a factory made board will give the best looking job in the end. But, as you're finding out, there is a price to pay to get there.

Etching your own boards has its own learning curve. I've used the Pulsar toner-transfer method for a couple of prototypes, but even so there was considerable labour and time to layout, etch, drill, etc. Perhaps you've got 8 - 10 hours a week for your hobby/after supper corporation so time spent etching, etc is time away from actual fabrication/experimentation/programming.

I've come to realize that if you estimate the cost of doing a board layout, etching, drilling, etc at say $35/hr you'll get a feel for whether it makes sense to do it yourself or use a service. With this as a guideline, I've been very happy with ExpressPCB.

As for a wired prototype, I use some of the pre-drilled, pre-etched experimenter's boards from RS just as you have done. They're the type that have traces already laid down for IC's, plus bus, neg bus, etc. When interconnections are required, I use #30 wire-wrap wire on the bottom surface.
Never as slick as a factory board, but serviceable.

An alternative is to visit a local university or college to see if they do small runs. Sometimes, students are willing to help out just to build experience. Also, is there a chance some of your friends might want to have a couple of boards as well? If you can get up to 10 or 15 boards, the costs come down substantially.

As with many things....if it was easy or cheap, you'd just get it at Wal-Mart!

Cheers,

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Tom Sisk

http://www.siskconsult.com
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T&E Engineer

Thank you Stamptrol.

I had forgotten about the protoboards that have the soldering pads on the bottom. I had been using the protoboards with only holes in them. For soldering I have either 22 guage stranded or solid wire OR 30 guage solid wire from Radio Shack. Since this project has ~300-600 mA running, I was was concerned if 30 guage would be able to handle it or not. I think I will give the 30 guage a try.

I have a couple of friends that have shown interest in the project but not sure if they would be willing to purchase one or not - certainly not if the PCB alone is $50.

I have time to work on these projects - just getting fustrated a bit at the cost factor.

Thanks again.

parts-man73

How big are these boards? I have some about to be manufactured, I could throw them on the same panel and split some of the cost with you.

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Brian Meade

"They who dream by day are cognizant of many things which escape those who dream only by night" - Edgar Poe

T&E Engineer

My board is not completely finished using ExpressPCB. I thank you for the offer but I will try the solderable protoboard concept first and see if it gets too difficult before I start spending more.

Thanks.

T&E Engineer

Surprisingly, all I needed to do was a different layout for the current limiting resistors to the (4) 8x8 LED modules AND the key was to use a Radio Shack perfboard (not protoboard) - the one with no solder pads but lots of holes with also using Radio Shack·30 guage wire. I finished the soldering tonight and tested it. I am using (32) 20 ohm resistors for the red and green cathode current limiting resistors. I am also using (4) 2803s for the cathodes and (2) 2982s for the 16 common anodes. All that is left is to solder this 5"x3.5" perfboard to my SX52 Protoboard which already has a DS1302 connected to RA.0-RA.2 (leaving RA.3-RA.7 free for push buttons to set the clock).

Tomorrow I will solder the SX52 protoboard to the perfboard and it should work (as I have tested every red and green LED).


I will post some pictures after the finished project is done - in case and all.

Eventually I want to replace the UDN2803s and / or ULN2982s with serial versions such as A6821s and TPIC6HC595s I have. This way it may be possible to do it all on an SX28. All that I/O down to a few lines. But for tonight...one step and day at a time!

Thanks again!

bobledoux

I use ExpressPCB to make my boards.

1. Layout on the green layer.
2. Display only the green layer and holes.
3. Change color of green layer to darkest black, background white, no grid.
4. Enlarge panel to full screen size.
5. Do a print screen.
6. Drop it into Microsoft Word as a picture and reduce to correct size.
7. Print it out.
8. Tape piece of toner transfer paper, using laser label, over printout and print again.
9. Apply toner transfer to board and run through $29 laminator.
10. Etch using 1-2 ounces of etchant and bitty piece of sponge.
11. Drill as necessary.
12. Remove toner with acetone.
13. Fill the board.

See here for more details:

http://www.pulsarprofx.com/PCB/a_Pages/1_Menu/overview.html

T&E Engineer

This is certainly good news.

However, why do I need a print screen to Word if ExpressPCB already prints it out to the right size?

One·problem I see with ExpressPCB is that when you print it out it also "may" need to be mirrored or flipped·so perhaps if a screen print is done, it can be taken in PAINT or something to do this.

I·am very concerned about having to resize this as I had to do a lot of trial and error to get all (4) 8x8 LED modules to line up perfectly next to each other.

Can you also explain steps 8 and 9 further. What is toner transfer paper and a laser label? Do I have to buy a $29 laminator? Office Depot? Walmart? I have a Brother MFC4800 laser all-in-one unit that can be used from home.

I have attached an unfinished version on my circuit if you want to play arround with it.

Forrest

>>Can you also explain steps 8 and 9 further. What is toner transfer paper and a laser label? Do I have to buy a $29 laminator? Office Depot? Walmart? I have a Brother MFC4800 laser all-in-one unit that can be used from home.

There are many ways to tranfer the image to the copper clad board. One is to use a very specific type of toner transfer paper and use the process outlined in steps 8 and 9. Another method that I've used is to use a laser printer/photocopier to print the image pattern onto inkjet photopaper and then using a regular cloths iron to transfer the image from the photopaper to the copper clad board as shown here www.veys.com/index.php/Making_Home-Made_Printed_Circuit_Boards

T&E Engineer

Thank you Forrest. I have both a photo inkjet HP7960 printer and an old Brother MFC4800 laser all in one. It wasn't clear if I needed to use either a photocopied image or use glossy paper on an inkjet printer.

I have seen something like this in the past but I thank you for this too.

Forrest

The important part is to use inkjet photopaper in a laser printer or xerox machine - because you need to tranfer toner to the copper clad board.