Getting By

Getting By

Getting By

A simple repository of largely nonsensical wittering. It may (or may not) be to do with what the Batsocks lot are currently using their Idle cycles for.

Packaging Pleasure

ElectronicsPosted by condemned Fri, March 16, 2012 14:55:39
In the past few weeks, I've received a couple of parcels which tickled me. They demonstrate the different ends of the packaging spectrum, so I thought I'd share some pictures.

Firstly, some Mega8A tqfp's that I bought on eBay from a Hong Kong seller. The are the cheapest Mega8's I've ever bought - superb value at around 80p each (including postage). As you can see, they're minimally packaged. A padded envelope containing a zip-top plastic bag with the bare chips loose inside. Amazingly, all the legs look undamaged and relatively flat (important for reflowing).


Secondly, a couple of XMegaA3's I bought from Farnell - one XMega192A3U and one XMega256A3U. These are 64 pin 0.8mm pitch tqfp's. Farnell aren't the cheapest supplier of these chips (especially in small quantities), but they have a low minimum order limit and have a UK base, so are pretty quick to deliver (a couple of days). These arrived in a huge cardboard box. In the cardboard box, surrounded by crumpled brown paper, were two waffle-trays, each vacuum packed in metallised plastic anti-static bags.
vacuum packed metallised bags.

desiccating bag

Just one chip per waffle tray


I am NOT complaining about inappropriate packaging here - quite the opposite. Each supplier delivered exactly as I expected. I'm delighted to have these diverse sources of parts available to me.

Re-sealing the metallised plastic bags
Since I'm not going to be using the XMegas for a couple of weeks (I'm waiting on a set of boards from iTead), I re-sealed them in their bags using a smooth-tipped soldering iron on high. Running the iron along a metal ruler gives a nice straight edge.

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Paste. Populate. Reflow.

ElectronicsPosted by condemned Thu, February 02, 2012 20:42:26
I took some photos whilst doing a recent batch of XMega PDI boards.
I was pleasantly surprised how well my camera caught the action...

Paste applied by stencil:
Notice the advanced (and purely by chance) side-lighting used to capture the depth of the paste. The polyester stencil was supplied by http://www.smtstencil.co.uk - who I'd recommend highly; lightning fast-turn around and a superb price.

Components populated:
You might think that the general mashing and smudgyness of the paste (caused by shaky-handed parts placement) would cause problems upon reflow, but that's not the case at all.

Reflowed:
I just wish that I'd got a way of videoing the reflow process. It's magical the way all the parts shuffle and hunker down to the middle of the pads by the force of surface tension.


In case that's not enough close-ups for you, here's a couple of bonus 1:1 pictures, unmolested from the camera:
The grainyness to the paste is the individual balls of solder. Bear in mind that these pads are 0.8mm apart.


Not bad for home reflowing!

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greyscale POV!

ElectronicsPosted by condemned Mon, December 19, 2011 22:12:47

I've just thrown together a little demo for an XMega...

It's a 4bpp (bits per pixel), 16 pixel high POV (persistence of vision) image generator.

It's just 16 LEDs connected to an XMega32A4.

The program steps through each slice of a bitmap (held in flash memory). For each slice, it toggles the 16 LEDs rapidly on/off to produce the light intensity required for each pixel. For gamma correction, it maps the 4bpp source brightness to a 6bpp output. The output is encoded as binary-coded-modulation.The whole pattern repeats itself when it gets to the end of the bitmap.

Here's a picture of the resulting effect:

And here's the original bitmap I used (before adding a strange blob for testing purposes)

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Amstrad NC100 fuse

ElectronicsPosted by condemned Wed, May 25, 2011 12:51:26
After throwing out my Amstrad NC100 in a big loft-clear out several years ago, I decided that I wanted one to play with again! Ebay came to the rescue with a (non-working) replacement. Fixing my new nc100 was relatively easy - the internal fuse had blown. As a temporary fix, a 0R 1206 worked very nicely. However, I've recently had to order some parts from Mouser, so included a suitable fuse...

Here are a couple of pictures of the new fuse being put in place...

Old 0R "fuse" removed...

New 0.8A fuse in place...

I can now sleep easy.

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Tiny ISP Adapter

ElectronicsPosted by condemned Mon, March 07, 2011 11:07:13
A quick and easy ISP adapter for an 8-pin AVR (Tiny13/25/45/85s)

I'm in the middle of designing a simple 8 LED meter/cylon sweep/POV kit.
At it's heart is a socketed Tiny13 (although I'll probably end up with a T85).
Because there's no room for an ISP header, I've been pulling the chip out of the socket each time I want to reprogram it (and I do that a lot when I'm developing code).

That was getting rather tiresome, so I've made myself a daughter-board that plugs into the socket...



It's just a normal turned-pin IC socket. I've drilled the holes in the board larger than normal, so the socket sits flush with the board (they usually sit proud). That means the legs extend just far enough on the underside to insert into the main board's socket...


It works nicely, and has significantly reduced my code / compile / reflash / find_stupid_error development lifecycle.

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Trust your instincts...

ElectronicsPosted by condemned Fri, April 02, 2010 09:54:20
I recently ordered some parts from Farnell, including some 10k 0603 resistors.

Normally I'd just peel back the tape and use the resistors, but something about these didn't seem right... So I measured them...



They're about 0.1ohm instead! Oops.

[edit: Farnell sorted it out very quickly - I had the correct resistors in my hands within a couple of days]
[edit: and here's a picture of what they should look like :]

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Smoking isn't good...

ElectronicsPosted by condemned Sat, March 13, 2010 14:44:25
I ordered a very cheap Nintendo Wii power supply last weekend.
I think it was a little too cheap.

I don't think power supplies are supposed to spark and smoke...


I'm glad it wasn't plugged into the Wii on it's first power-up.
I've asked the retailer to send me a replacement. I'm not sure that's wise!

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