[Fwd: AW: The merlin project. Update and tip.]

[The Dark force of dance]

Y-ellow Robin and Diodes.

At 01:55 PM 2/10/98 +0000, robin bussell wrote:

>Well metal films are (or at least *were*) ceramic tubes, coated on the
>outside with the resistive film. Sometimes , for the higher values I suppose, 
>this film would have a helical groove etched into it so that the resistive 
>film actually ended up being like a ribbon wrapped round the tubular substrate.
>Filing one of these at the wrong angle or in the wrong spot could give you an
>open circuit fairly quickly.. so you can file 'em but sometimes you might get
>a bit too much extra resistance all of a sudden :-)

hmmm. Point taken. I guess what I need to do is pull a resistor apart more
carefully and take a look. But having said that, whilst I found that metal
films were a harder material to file than carbons, I was still applying very
little preasure to the file. Just saving off a little of the surface at a
time. And it should be worthy of note thus.

Unless you're really stuck for a resistor value, you should chose a value
that is as close as possible to the ideal value but less than it. Thus you
onlyneed to file a little bit to bring it up to the target value. I'll do a
little more investigation on this when I get the chance. I'm bit more
facinated by the mechanical nature of these beasties now. 

>What you're doing is essentially the same as the automated 'laser trimming' you
>see boasted about quite often.. I wonder if we can come up with a suitably
bombastic
>term for filing... something like "individually hand trimmed by frictive
attrition"
>:-)

Heh Heh. Actually I had also previously mentioned this but you got in first.
I actually wrote it yesterday but by the time I got to log in and post it
you'd beaten me to the line. I remembered where I'd seen this in a
technology I actually use. That's in NSC's digital controlled graphic
equalizer chips. They have a string of laser trimmed resistance ladders for
each EQ band.

>P.S. talking of silly putty... what's it like as a dielectric? have you
thought 
>of making a foil sandwich and seeing what sort of sensor/controller it'd make?

Oooooo. I wonder if you could make some kind of plyable capacitive element?
You could use it as a sensor in a power glove. Or what about instead of a
strain gague, what about a "bounce gague"? :) You could use it to see how
many "G"s your crockery could withstand before it breaks. :) This could be a
whole new field of science. Err. Consumer Science? I think we've just
invented the Brittleometer! Race you to the patent office. :)

Anyway thanks for that. "Careful with that file Eugene." :)

be absolutely ICebox.
 _ __        _                              
| "_ \      | |         batzman at gist.net.au / aek at gist.net.au
| |_)/  __ _| |_ ____           ALL ELECTRIC KITCHEN               
|  _ \ / _` | __|___ |  The new AEK CD, Elementary Urban sanity    
| |_) | (_| | |_  / /   is out now on Transmission Communications from
|_,__/ \__,_|\__|/ /    http://brisbane.dialix.com.au:80/~com11
                / ,__   and check out http://www.all-electric.com
Goodfortune    |_____|       Let your SANITY wear thin.