PCB Overlay Artwork on a 9 Pin Printer  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  Bob Mitchell   ¿? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿? The aim of this article is not to advocate the use of a 9 pin printer as the best method of outputting high quality printed circuit overlay artwork, but to show that in a pinch, it is possible.  - - - - - - - - - - After reading the article on the "Joyswitch" by john Olsen in issue 31 of MegaDisc, I thought that it was such a good idea that I would build one for myself. I could have just put one together on a piece of veroboard, as suggested by John, but I thought that with all the power of the mighty Amiga at my fingertips, producing such a simple board overlay would be a breeze. Hmmmm. OK firstly, I don't own a $X,000.00 PCB CAD programme. Well its only a black and white drawing, surely an art package like Deluxe Paint could handle such a simple task? After loading up DPaint, ready to make a start, I realised that I had no way of accurately estimating the size of the resultant printout. So if the pins on the IC's were going to line up with the PCB holes this major difficulty would have to be overcome. A few test printouts later I also realized that the resolution of the printouts, even in high res, was not up to the task. (you can't have jaggies on PCB's it looks RS) That's when I remembered a programme, from MegaDisc Topix Disk 20, called GPrint written by a Canadian named Peter Cherna. GPrint is a black and white graphics print utility for Epson FX printers. It uses a special print smoothing algorithym which produces exceptional quality printouts from a 9 pin printer. Back to DPaint! What I now needed to do was to draw a matrix of dots in the Hi Res mode at varying intervals so that I could determine the appropriate pin spacings for the IC's after the artwork was printed, relevent to which mode for GPrint is used. To cut a long story short, after much trial and error, I found that if I used a matrix of 24X by 22Y on DPaint, and printed out in GPrint's Ultra mode I could match the pin spacings on standard IC's up to about 10 pins. After this the error starts to become too great, and you start to get alignment problems. This is not really a problem though, because if you want to make boards for IC's with more than 20 pins, you should be using a proper PCB CAD proggy, and a plotter or laser printer for the job anyway. If you set the grid function coordinates in DPaint to 24X by 22Y, and use the grid tool, it becomes a simple task to place PCB pads in the correct positions to match up with the IC pins. ie the IC pin pitch is 24 pixels in horizontal direction, or 22 pixels apart in the vertical direction. Also, when routing angled traces to the pads, if you stick to 45° angles you will find that the lines will be much smoother when printed, because of the single pixel deviation (ie. smoother jaggies). Another thing that can have a fairly dramatic effect on the printout quality, is the actual condition of your printer ribbon. When I made my boards, my printer ribbon was fairly dry, so that there was minimal smudging, or bleeding of the image. This problem can be overcome in most cases by simply using smaller pads, and finer traces, So that ther is greater separation between conductors. Making a photocopy of the image can also help to sharpen the edges a bit as well. If you want to see for youself how good the print quality is, try using the example board design, with GPrint in Ultra mode.  ie. >GPrint J_M_Board.pic U C The images produced by this method can then be used with any of the photo resist products available from places like Jaycar or Dick Smiths in the same manner as the artwork you find in any of the electronics magazines. This method worked so well, that I was able to produce the artwork for the JoySwitch PCB on my Epson LX-400 9 pin printer. It was printed to actual size, and of a high enough quality to be used to manufacture the actual PCB's. The resolution is so good that I was able to have some traces running between the IC pins, and there were only a couple of minor separations required on three out of seven boards produced. I have subsequently made a JoySwitch, using one of the boards, and it is currently fitted to my Amiga and works perfectly. Also I have included one of the boards, and some example printouts with this submission to Tim, for him to verify the results of all this messing about. As with all these type of projects, all the warnings about stuffing up your computer due to not paying enough attention to detail, or not posessing the required skills apply. Also, if you do decide to use the particular design described, and end up stuffing your computer for the afformentioned reasons, or others, be it on your own head. But like I said, it works for me. By the way, GPrint is shareware, and if you use it you are asked to forward a registration fee to the author. Last but not least, full credit to John Olsen for his design. But I am just a small bit curious on the legitimacy of a copyright on a circuit using basic generic components assembled in a perfectly normal manner. It's a bit like taking out a patent on the idea of attaching a sprinkler to your garden hose. On the other hand it would be perfectly normal to obtain a copyright (patent?) on the design for a PCB, there being much greater leeway for design improvement with regards to size, ease of manufactur etc. ( no mines not copyright, or patented )  ____oOOo____oOOo____  L____L____L____L____L  ___L____L____L____L__  L____L____L____L____L  Tks.  ¿? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿*? 35 ¿?