Altronics Colour Maximite - Mystery Cap


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Geoffg

Guru

Joined: 06/06/2011
Location: Australia
Posts: 2953
Posted: 04:32pm 08 Dec 2012      

Ah, all excellent points and I think that you will have to blame me for that.

Firstly, it had to be an SMD capacitor.

That particular capacitor (connected to Vcap on the PIC32) is critical to the smooth running of the PIC32 and has caused a lot of grief for constructors. Microchip originally specified it as 10uF tantalum or ceramic so in the original Maximite I used a 10uF tantalum. You might remember that it did not work for some constructors and there was a debate on this forum about adding extra capacitors (some wired to +3.3V) to get the PIC32 running.

In the mini Maximite I tried a higher valued tantalum but the real solution is to use a ceramic as they have a much lower internal impedance. The trouble is that 10uF ceramics are only available in SMD packages - so that was why the Colour Maximite has an SMD capacitor.

I should have made a bigger point on soldering that cap in the article but, because I assumed that the constructor had soldered the PIC32, I thought that the cap would be easy. The other point is, if Altronics soldered the PIC32 why did they not solder the 10uF cap?

A few years ago I was leery of SMD components but I have no problems now, in fact I find them easy (http://geoffg.net/SurfaceMount.html). Obviously I need to keep in mind that SMD is still new to some.

Your comments are interesting in another way. I am currently designing a GPS tracking device which will probably find its way into Silicon Chip and I have been debating the package to use for a low Rdson FET. The SMD version costs about 20 cents while a thru hole version (in a huge TO-220 package) costs $2.80. After your comments I think that I will design the board to suit either.

It must have been a thrill when you got the Colour Maximite going and your logo came up on the screen. I hope that you enjoy colour and I bet that there will be a lot of people looking forward to MaxMan in colour and other stuff.

Geoff

Geoff Graham - http://geoffg.net