Phillip Pearson - Second p0st

tech notes and web hackery from the guy that brought you bzero, python community server, the blogging ecosystem, the new zealand coffee review and the internet topic exchange

2004-1-7

Microcontrollers

Here's another couple of CPU possibilities: one from Atmel, and one from Microchip:

First, the South Island Component Centre stocks a bunch of Atmel CPUs, including the $4.77 ATTINY12-8PI, an 8MHz 8-pin micro with 1kB of flash and 6 I/O pins. You can program these with an Atmel port of GCC if you don't like their assembly language.

Second, from Microchip, I can get the PIC12F629 chip, in the guise of the PICAXE-08. Also the 12F675 is available. The cool thing about the PICAXE-08 is that it has an ultra-cheap prototype board to make playing around easier. CPU + board = $15 incl GST. It might need a $10 download cable too. The disadvantage is that it only has 128 bytes of program memory, so only really small programs will fit.

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Home automation notes

The PIC16F628 seriously fails to suck. All the features of the 16F84 and then some, and US$1.80 each for 25+ at Digikey. By the time a batch of 25 would make it to New Zealand, that's about NZ$5 each. I may be out of date, but this seems about 20-50% of the cost of comparable AVR chips. They don't look as efficient or easy to program as the AVRs, though. [The AVRs execute one instruction per clock, and I built a parallel cable to program them a while back that only needed two transistors.]

OpenPic.Net is a complete DIY home automation system that uses the 16F84 (or 16F628). It's controlled by a PC, and uses a star-connected serial bus for communications (very simple protocol, at about 500 bps).

Now what I need is a slightly safer / better equivalent of the OpenPic.Net switched power plug. I don't like the look of the solid-state relays they're using; I'd prefer an optocoupled magnetic relay, to make things less catastropic in case of a fault and to allow switching beefier devices.

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Camera choices

Just before Christmas, I managed to destroy my Casio Exilim EX-S2 camera. The repair will cost either about $150 or about $600, depending whether the main circuit board is screwed or not. I'm not sure if I want to risk the latter bill, so I've been cameraless for the past few months.

Now I'm looking for a replacement. Here are the choices so far:

  1. another EX-S2 (off eBay; 2MP; small) - about NZ$300
  2. an EX-S3 (new; 3MP; small) - NZ$580
  3. an EX-Z3 (new; 3MP; optical zoom) - NZ$650
  4. a Pentax Optio S (new; 3MP; optical zoom; smaller than EX-Z3) - NZ$700

I can't decide whether I want to go for another small/slim camera (EX-S2 or EX-S3), or for something with optical zoom (EX-Z3 or Optio S). My father has an Optio S, and it looks good, but it's quite big compared to my old EX-S2. The EX-S2 permanently lived in my shirt pocket, so it was always there when I wanted to take a picture, but I'm not sure if I could do that with either of the EX-Z3 or the Optio S.

(Note: NZ$1 is about US$0.50-0.70, depending).

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