Half a YAPP - mini-mast display

I have implemented some backlight stuff. I don't know why I didn't think of it before, but the easiest way to control the backlight without an external button is to use the incoming light control messages via Seatalk. So now when you change the brightness on any of your other displays it changes the brightness on this one too. The now defunct mast display project does just that, so I don't know why I didn't think of of for this one.



(Well that video is just pants, but it does work really. All 3 lighting levels are fairly low as needed on boat instruments and the camera just isn't really capturing it.)

The backlight is controlled by a PWM output from the processor driving a MOSFET. Now I don't have the MOSFET I am intending using and I don't want to make a RS order for one part costing 13p, so if someone else would like to try it I'd be grateful. The MOSFET I am proposing using is RS part 719-2881.

I have also noticed and fixed some copy and paste errors in last week's effort. I sent it out too soon - bug in the schematic and now the software as well. I'll send updates. The schematic will have the new backlight stuff, but it will still work without the extra circuitry.
 
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I do PCB design work when no-one is looking at work... Then it will take a month to get them.
What software do you use?

I can make SS boards at home, in low quantities. The most time-consuming part is drilling the holes; one reason why I'm moving to SM components where possible; I can just about manage an 0805, but 1206 is easier.
 
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Update - finally got round to building it:

http://i1168.photobucket.com/albums...3CD95AE-2085-00000358729A0684_zps9d30361e.jpg
(flying green wires are for a pushbutton to control backlight power, nothing to do with the YAPP circuit as such)

Also managed to build the code (had to tweak a few things to work on MPLAB X on Mac) and program the chip, which appears to be running (according to what the debugger seems to be saying).

Sadly, nowt displayed on the screen :(

I assume this would be due to a mistake in converting from the circuit diagram to the board layout, or a fault in soldering the board, but I don't really know where to start looking. Unfortunately, not being a real electronics person, I don't have any diagnostic kit more sophisticated than a basic multimeter.

Pete
 
Where you have removed a Veroboard track section check with a multimeter that there is no continuity across the hole. Also check that there is no continuity between neighbouring tracks. It's very easy for a sliver of copper to cause a short. Then check that there is continuity between each processor pin and display pin. If that doesn't work you will have to wait for this to come back from China...

67156791.jpg
 
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