[Robotgroup] Printing PCBs

[Gray Mack]

I highly recommend the photo etch process, once you get the development process down the results are very good. It requires pre-sensitized boards.  Frys sells them for I think $13 for a 6x9 +$2 for double sided. You need a bottle of developer (maybe $10) and the development light kit (maybe $30). print the tracings onto a transparency. Expose the board to light with the transparency on it. Develop the board and wash it. Then it etches in ferric chloride just like any other trace resist etching.
I have a dremel press, the only thing I dont have is a way to cut the boards (best done after etching since you cant expose this kind of board to light before hand).
If you want to defray the costs I recommend getting a signup list of who wants the boards beforehand. Its hard to tell how many H-Bridges are needed by TRG folks.

My experience with this chip is that it will drive a 6v battery/motor from a 5v logic supply and run cordless screwdriver motors. I didnt try letting the battery sag down below that or stalling the motor outputs to see if it went over 2 amps or whatever the max was. To use the sense feedback on the chip you have to use a current shunt, I dont know if something like a fuse will work for this. Overall it seems like a good circuit to have laying around on your bench.

-Gray

----- Original Message ----
From: Clendon Gibson <bsandyman at yahoo.com>
To: Austin Robotgroup Mailing List <robotgroup at puremagic.com>
Sent: Monday, May 7, 2007 9:54:27 AM
Subject: [Robotgroup] Printing PCBs


I am thinking of getting the gear together to make single or maybe double sided PCB boards. The techniques I was taught back in the day was to use copper boards coated with photo-resist. It looks like I can get a complete kit of this including some starter boards for $70-$80. 

In particular I am wanting to make this board for the L298 dual H-Bridge:

http://www.dprg.org/projects/1998-04a/

I am thinking that if I can sell 7 or 8 of these boards to interested RG members for maybe $10 a piece I can cover my costs and provide a useful service to the group.

What I don't have is a drill press or a means of cutting the finished boards. So would anyone be willing to provide the drilling and cutting in return for a board or two, or some fee?

Of course some members may be happy to do the cutting and drilling themselves.

If there is interest please let me know. I would also be open to printing boards from anything you can print on a transparency.


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