I've been told by several who are "in-the-know" that for RF work, resistors in the high-tens-of-K to hundreds-of-K range have lower stray capacitance. I've been unable to discern any difference myself (note that I'm obviously excluding myself from the "in-the-know" camp.)
Catalog house pricing is increasingly showing higher prices for Megohm-and-bigger resistances. In a couple of cases they've just stopped carrying them in leaded packages. They're not all gone but the trend is a bit worrying (I don't trust any of them since the CA3046 was discontinued!)
When I'm not using tinned or untinned copper PCB for enclosueres/partitions I'm using brass sheet and occasionally short sections of 1" diameter thin-wall brass tubing.
Where does brass fall into the grand scheme of things? I kinda like it because it bends (unlike most PCB) and it doesn't corrode/oxidize nearly as fast as bare copper does.
I looked into that for my current project. When I actually flow charted the program and looked at it with my moldy oldy "ands and ors" mind I could do this with a few chips and there might be a chance in
10 years that someone else on the planet could figure out what I did. Anybody can plug in a chip, all they have to do is line it up right. How many "service" people have the means, skill and equipment to reprogram a PIC?
To support a component junction, you solder a 10-meg 1/4w resistor to the copperclad, and use its free end as a tie point. This is just a leaky spacer. Caps work well too, especially if the node needs bypassing anyhow.
OK, everybody post pics of their prettiest/ugliest breadboards to a.b.s.e.
For RF, "manhattan construction" Example (not mine):
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You punch pads of PC board. These are glued or soldered on to an unetched PC board, giving a 100% ground plane. Components are connected at the pads. Page 23 of
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shows the idea, and the article is a "how to".
For "try it out" items, whatever. Prefer pad per hole. For "keep it" I etch a board.
For high current, I make a board using copper flashing made for roofing. It's thicker than a PC board trace, and I cut wide strips. Contact cement the strips to the board where I need "traces".
Yes... a 10-meg resistor is basically an antistatic spacer, right?
As I understand it, the resistance between 2 random unconnected points on a circuit board, maybe 1 cm apart, is likely to be 20 to 100 megohms, right? So a 22-meg resistor really is a spacer.
Sheet brass is pretty good. Its conductivity isn't as high as copper, by quite a bit, but on the other hand you use much thicker sections. Its thermal conductivity is low enough that you don't need a Godzilla soldering iron. For RF shields, it avoids the problem of having to make the shields continuous on both sides of the copper--how many of us here have been bitten by leaky shield boxes caused by soldering the wrong side of the copper clad board someplace?
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The prototype box that I've used the most over the years has a bunch of tip jacks and a socket for a zero-power 22V10Z PAL, plus one BNC jack for clock and a LEMO for power.. I'm forever doing some gizmo that needs really accurate timing with mildly complicated sequencing, and zero-power PALs are the cat's pajamas for that. It's sort of an intermediate state between random logic and PICs, and is very useful for those awkward interleaved control and data acq tasks that take *forever* using DAQ boards.
One project I particularly liked was an endpoint sensor for post-exposure bake of chemically-amplified photoresist for chipmaking--it used the bake time as a process parameter to improve the critical dimension control in memory chips. The idea was to look at the diffraction pattern from the latent image in the photoresist, and stop the bake when the pattern was just right. This improved the process window for 4 Mb memory chips significantly. (Okay, it was a while ago, sue me.) The diffraction pattern was hexagonal in structure, but could be oriented at any angle.
All it had in it was a 22V10Z, seven small solar cells, an op amp TIA, and a LED, plus a DAQ board. All the solar cell cathodes were connected to the op amp's summing junction The 22V10Z's tri-state outputs went to the solar cell anodes. The 22V10 went round the solar cells, connecting one to the TIA by grounding its anode while leaving the others open-circuited, then triggering the DAQ board. A common-base stage on the input of the TIA allowed the solar cells to work up to about 20 kHz bandwidth, which is pretty radical for a solar cell.
Using seven solar cells meant that we wouldn't ever have all the diffraction spots split between two solar cells, which would have happened a lot if we'd only used 6 solar cells.
Thanks to all who answered. I have been following the links and I think I am going with the boards with the horizontal rows of connected pads extending from DIP pads. That looks like the easiest and I found AllElectronics.com has them for a few bucks each.
I don't do PCB layout for a living either. But at work I've laid out about
6 simple boards using their software. It's very easy to use. They even have a hokey little schematic entry program, and you can link the schematic to the layout so that connection information is available. They don't actually have a rat's nest, or a design rule checker, but you can click on any pin or pad and highlight the whole net.
Of course, you don't get Gerbers from them, and so you can't easily switch to a new vendor or get anybody else to bid on the PCB fab. But for simple boards and low volumes that isn't really a problem.
Personally, I don't really do prototypes any other way at work. It's just too easy to get the PCB straightaway.
Sometimes we later give the layout to some local guys and have them do a real board with Gerbers and everything.
Anyway, ExpressPCB has always delivered boards as specified and on time for us.
Until very recently I used tagboards and tagstrips.
The smallest size of tagboard supplied by R.S. Components had enogh room between the two rows of tags for me to drill a pattern of holes to take IC sockets. The pins were then brought out onto the tags. These could be wired lengthways and across the board and on the diagonal; with components on both sides of the board..
The result was often quite a bit smaller than I could achieve with a PC board, because I was working in three dimensions. My best ever was six microphone preamps in a space 1" x 1" x 4", complete with all DC and RF blocking components.
Sadly, R.S.Components have discontinued all their tagboards and all their tagstrips, so I have been forced to use Veroboard (or short-circuit board, as I now call it). The space required for simple equipment has increased enormously, at least half my construction time is now spent tracing and clearing shorts or open circuits ...and I have a steadily-growing pile of damaged components because of it.
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