OT-ish: Build-it stuff

Tony Duell ard at p850ug1.demon.co.uk
Tue Jun 13 17:58:12 CDT 2006


[Resistors]

> When I need a value I don't have, I usually order a strip of 50 or 100 of=
>  the=20
> 0.25W metal-film variant. =A31 +VAT for fifty resistors - certainly beats=
> =20
> 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=
>  it=20

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=
> y=20
> 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=
> .=20
> Mainline were great up until their warehouse caught fire, Greenweld have=20
> disappeared (good riddance, their Innovations-catalogue wares will not be=
> =20

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=
> hey=20
> 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=
> o=20
> > 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...

> When=20
> I need to put a particularly fussy chip onto a breadboard, I make an adap=
> ter=20
> in Autotrax and etch it. It takes longer, but it beats dead-bugging fine-=
> pitch=20
> chips.
> 
> 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 =
> about=20
> how cheap their ICs were. I asked how much the development software was, =
> and=20
> got the answer "sorry, we can't tell you unless you sign an NDA." Sorry, =
> wrong=20
> 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)=
>  -=20
> 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 
it. 
> I don't really do wirewrap or Roadrunner wiring much these days. My last =
> three=20
> 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.

-tony




More information about the cctech mailing list