Monday, July 18, 2005

Re-comencement & front-panel design

Well, it been a long time since I've made an update and whilst there hasn't been much progress there has been some.

Back in March I was stating to try and choose the PIC and I had to make a decision about the method for selecting the MIDI channel. Clearly Omni mode is useless in a set-up with a few different MIDI instruments. Also, I didn't want to have a fixed channel as this too can cause complications. So I was trying to decide how best to make the channel selectable - would I have a rotary switch or a pushbutton and LED display arrangement. There was problems with both and I decided I needed to see what space was left on the front panel. I also wanted to get the mock-up front panel in place so that I could fix the PCBs in place.

I had decided to get an aluminium panel cut and engraved by Schaeffer (http://www.schaeffer-ag.de ) and so I set about laying out the panel using their excellent free program. I soon ran into problems though.

In order to produce a pleasing and profesional looking final panel I don't want to put screws through the front panel. Nor do I want to fix pots to the front panel. The correct way to do this is to have a sub-panel behind the front-panel with all the controls fixed to that and then the frontpanel is kept clear for all the text and markers. Schaeffer can fix bushes (clinch nuts) to the rear of the panel so I can fit the sub-panel(s) to the back of front panel. Great! Let's designing.

If you look at the pictures below you can see that the pot's are already fitted to sub-panels. This is how the SS30 was built and is another reason to go with the sub-panel idea. When I sat down to try and lay-out the front panel I had to ensure that the holes for the pots were kept in line with these sub-panels. Also the position of the bushes has to be lined up with the fixing holes. This was starting to get tricky as the positions had to be relative to each other. On top of this the space on the front panel is tight if I want to use the orignal chunky tablet switches so the placement of the sub panels and switches needed some fine tuning. I needed templates for the sub-panels that I could move around and line up. This a bit of stretch for Schaeffer's Front Panel Designer (FPD) program so I decided design templates for the subpanels in AutoCAD and then I could slide everything around till it fitted. Luckily my partner is a dab hand at AutoCAD and she had me up and running in no time.

It took some time but eventually I had all the SS30 sub-panels and switches placed. I could then take the co-ordinates of all the holes from AutoCAD and transfer them to FPD. Finally I put all the text and marker engravings on the design too, using teh original SS30 panel as a guide.

So this is where I've got to. I'd like to post up an image of the panel but I need to do a screen grab as you can't print to file or anything like that in FPD. Eventually I'll put up the screen grab and a link to the actual FPD file.

That all took me a couple of months but I've done nothing for the last two months owing to other things taking priority.

Next : I need to get a print out of the design from FPD then paste that onto a piece of MDF. I can then drill and cut all the holes to a) check the measurmenets and b) have a mock-up that I can use until I take the plunge and get the real panel made.

But what about the MIDI channel control? Is what room is there? Well, I'm 90% sure that I'm going to for a push-button and LED arrangement but I need to check whether the PIC has Non-volatile that can remeber the setting. If not, then it'll have to be some sort of mechanical switch.

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