Date   : Sat, 03 Oct 2009 18:31:25 +0200
From   : rick@... (Rick Murray)
Subject: RR09 Photos (Day 2)

Jonathan Graham Harston wrote:

> Have you looked inside a central heating boiler nowadays? 

:-) Our "central heating" as a log fuelled fire and lots of hot water 
bottles.


> When I  helped my dad put his in in 1975, central heating control
 > was effectively three switches in serial controlling a gas valve:

That's what I remember from the unit back in England. The overheat 
cutout was never 'right'...


> It's a veritable computer in there. The plumber had to take the
 > PCB back to the supplier because a microcrack on the board
> kept causing it to crash on startup. (!)

Not what you want in a heater!

But - question - is it any better? For all of the complexity in the 
doors at work, if you walk through the door while it is up, such 
activity does *not* reset the internal timer. The yellow lamps will 
flash, the door will go down a few inches, THEN it will notice traffic 
and go back up again. Whole g***amn computer and something so basic is 
still wrong...

There IS an argument with car ignition controls, it "shapes" the spark 
and works out how best to do the mixtures for engine temperature, speed, 
blah blah.

But your central heating - does it do something special that a simpler 
mechanical system couldn't do? Our old heater's timer had ON/TIME/OFF, 
it could run two on/off zones per day (like 8-10am, 4-8pm or whatever), 
plus the option of water/heat/both. Simple mechanical timer. The ONE 
time it failed, I took it off the wall. I cleaned off a little gear 
wheel, a dab of three-in-one oil, fine. Oh, I was about 12 at the time.


You'll see this a lot in my methodology of thinking. Things that are 
complicated should be "simple enough", rather than "complex enough". 
We've already been here with the ideas of making a homebrew teletext 
inserter (any progress there?).


Best wishes,

Rick.

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...