OT-ish: Build-it stuff
ard at p850ug1.demon.co.uk
Tue Jun 13 17:58:12 CDT 2006
> When I need a value I don't have, I usually order a strip of 50 or 100 of=
> 0.25W metal-film variant. =A31 +VAT for fifty resistors - certainly beats=
> Maplin's extortionate 70p for ten.
You're missing the point. If I know I am short of a particular value, or
will need a lot of them (like the time I needed about 100 33 Ohm
resistors when I was filling up a Unibus memory board...) then I order
them from RS or Farnell, or somewhere.
But I have, on serveral occasions, been designing anf prototyping
something and found at the last minute that I need, say, a 390 ohm
resistor. I don't have one in the junk box. In the old days, either in
London or Bristol, I'd hop on a bus and get 10 from Maplin. And be
designing again within the hour. Now I have to send an order to RS or
Farnell and make it large enough to meet the latter's minimum order
charge or so that the former's postage charge doesn't exceed the value of
the components. OK, there are always components I can use, but finding
the money every few days gets a bit much!
> I've still yet to find a place that sells nickel shim stock though (I use=
I don't know of anywhere off the top of my head, but I'd look in Model
Engineer magazine (and its companion Model Engineer's Workshop). Both
should be in Smiths. The advantage of model engineering suppliers is that
they're used to dealing with hobbyists who want small-ish qunatities (the
place I get metal rod from -- GLR Distribution -- cuts it to the nearest
foot (or 30 cm, or something like that). Yes, it's more expensive per
unit length than an industrial metal supplier, but I don't want several
hundred feet of the stuff!
> for battery welding strips). I used to get it from McMaster-Carr, but the=
> won't do export orders any more.
That's another thin that annoys me. Companies who won't ship to the UK
when there's no good reason that they can't (no import restrictions on
the goods, no problem in posting them, etc).
> Now what I would like to find is a decent supplier of electronics surplus=
> Mainline were great up until their warehouse caught fire, Greenweld have=20
> disappeared (good riddance, their Innovations-catalogue wares will not be=
I rememebr when Greenweld were down in Southampton and had some
interesting surplus. Every year they had the half-price summer sale, I'd
get on the train from Bristol (a nice ride though the country, down
through Bradford-on-Avon, Romsey and Salisbury), and come back with as
much stuff as I could sensibly carry. I can't rememebr all I bought from
them, but I know my first HX20 came from there. As did some interesting
6809-based Microvitec colour terminals
> missed) and WCN don't seem to have much useful stock these days. Nor do t=
> seem to want to send me a copy of the current catalogue...
But is there much surplus stuff still around? We've already discussed
the fact that modern stuff is not really repairable. It doesn't contain
many recognisable componets. What are you goign to do with a PCB
containing a few PQFP (or worse BGA) packaged ASICs?
> > One thing that's not helped are that ICs now come in hacker-unfriendly=20
> > pacakges, and may require expensice programming software and hardware t=
> > do anything with.=20
> I've got a box full of homebrew adapter PCBs and turned-pin solder pins. =
Hmmm.. I don't fancy doing that for a BGA pacakge...
> I need to put a particularly fussy chip onto a breadboard, I make an adap=
> in Autotrax and etch it. It takes longer, but it beats dead-bugging fine-=
> On the software front, I just ignore anything that needs expensive softwa=
> re. I=20
> once had the 'pleasure' of dealing with an FPGA vendor who was screaming =
> how cheap their ICs were. I asked how much the development software was, =
> got the answer "sorry, we can't tell you unless you sign an NDA." Sorry, =
> answer, you lose, thanks for playing.
> There's a reason all the microcontrollers in my junkbox are Microchip PIC=
> s and=20
> 8051 derivatives (mostly Dallas Semiconductor "Speed It uP" series chips)=
> free or cheap dev software. MPLAB is free, MetaLink Assembler is free too=
> , and=20
> the Dallas chips are programmed with a MAX232 and a toggle switch. All my=
Microcontrollers are not the problem here. For most (if not all) of the
popular ones, the machine code is docuements. You could, if pushed,
hand-assemble the firmware (although even I, a confirmed non-programmer,
would probably write a cross-asssembler). Quite a few have documented
programming algorithms (you can make your own programmer), or can run
from external EPROM (and you can make your own EPROM programmer...)
No, the problem is programmable logic chips. I've yet to find one of any
complexity above a simple PAL/GAL where you can go from logic equations
to chip without either a proprietary compiler (which even if free, will
run on a most definitely non-free operating system that I don't have), or
a proprietary programmer, or both.
Actually, I don't need, or even want, programmable logic, but since a lot
of interesting TTL is no more, I guess I'll have to do something about
> I don't really do wirewrap or Roadrunner wiring much these days. My last =
> projects were built straight onto PCBs, then I patched the inevitable bug=
I guess you design differently to me. I like to build a bit, test it,
build a bit more, and so on. That's a lot easier to do with hand-wiring
than with a PCB.
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