I do a lot of one-off things (they're for my own use, not particularly anything the general public would find useful). A PCB would be a waste of time, and as Tony mentioned, not amenable to easy modification without doing a new run. I still use wire-wrap. The finished product is easily modifiable and will turn in reliable performance for as long as I care to use it. --Chuck

Chuck Guzis wrote: I've got the tools to do wire-wrap, but none of the boards, sockets or hardware (it seems WW IC sockets have become rather difficult to source). The long pins also tend to get in the way IMO... To be honest, I prefer the RoadRunner point-to-point wiring pens. They're a bit like wire-wrap, but you use enamelled copper wire which is soldered to the component (or socket) pins like a PCB "ratsnest". Though admittedly it is a good idea to use wiring guides (aka "wiring castellations" -- they look a bit like the battlements on top of castle towers) to keep the wires tidy. I usually have one of these between each row of ICs, then route all the wiring inside them -- it keeps things much tidier, though it's not as easy to trace a fault. Replacing resistors etc. is usually best done by nipping off the old component pins at the body of the part, and soldering the new part to the stubs... it's very much a one-shot prototyping system. One of these days I need to find some software that can take an CAD netlist and produce a wire-wrap wiring list using the "top and bottom" technique (that is, wires are "on top" at one end and "on the bottom" at the other, thus making any changes possible with the removal of at most one wire). I know this has been done in the past, though I don't think any of the EDA software that did it has survived... :( (Even if it was designed for Wire-Wrap, it might be useful for the Roadrunner system too) -- Phil. classiccmp at philpem.me.uk http://www.philpem.me.uk/

[Wire-wraped prototypes] ... and generate enough static to zap every MOS device in the system. -tony

From: "Philip Pemberton" Monday, April 26, 2010 2:32 PM I have a Perl script that can do this, from the Eagle exported netlist and partlist (to get the locations and package styles of the various parts). For each package style (DIL14, 0207/10, etc.), you must write a simple Perl function to specify the X and Y coordinates of each pin. What you get out is a list of level 1 wraps and their wire lengths, followed by a list of level 2 wraps and their wire lengths. It treats GND, VCC, etc. as signals, but generally you can just ignore those and route the power busses by hand. By way of example, here's a single signal excerpted from a run on the TC08 drawings (stuff wired to a pull-up resistor at A09.U1): Level Signal From To Length ----- ------ ---- -- ------ L1 +3V at A09U1 B13.U2 B13.R1 3in. L1 +3V at A09U1 A07.T2 A07.S2 1.5in. L1 +3V at A09U1 A08.K2 A08.F2 1.5in. L1 +3V at A09U1 A09.U1 A07.S1 2.5in. ... L2 +3V at A09U1 B13.R1 A07.T2 4.5in. L2 +3V at A09U1 A07.S2 A08.K2 2in. L2 +3V at A09U1 A08.F2 A09.U1 1.5in. L2 +3V at A09U1 A07.S1 A08.D1 3in. ... Where B13.U2 means pin U2 of component B13, etc. It shouldn't be too hard to fiddle the distance metrics for the type of wire routes you plan to use. Vince

On 4/26/2010 12:25 PM, Tony Duell wrote I'm not sure that's a valid reason. It's pretty easy to make mods on a PCB as well, unless the initial design is really FUBAR. If (and a big IF) someone is very good at reading pin numbers backwards, has good prototyping skills, and doesn;t get in a hurry, I'd say the prototype direction wins. But, I can see that swinging in favor of PCBs very easily: * It's easy to get messed up while looking at the back of a board as to pin numbers. Sure, they make guides for that, but then that's just another product you need to have in your kit. * You still have to design it in something (napkin, graph paper, etc.) For ultra simple (<10 major components) designs, I can see the napkin as OK, but beyond that, hand drawn schematics (that don't take as much time as a PCB app) get hard to read and prone to error. * Moving from idea to prototype can be addictive to the point that corners are cut, creation is done in haste, and then mistakes are made Probably the most important reason * wirewrapping and such don't work nearly as well with SMT. You either need to buy SMT->through hole adapter boards (another item to stock in the kit), or use kynar, glue, and a patient hand to solder a "dead bug style" SMT IC to your prototype The last item is what drove me to PCB for all my projects. Many newer parts only come in SMT variants. Jim

But it's certainly a lot hardwre to make an 'incremental design' on a PCB. Which viertually all my projects are. I have never hand any problems with this. But then I can easily read upside down and mirror-reflected text without really thinking about it. IC pins (at lest DIP and SOIC pacakages) are numbered anticlockwise (counterclockwise) starting from the 'notch'. There's a reason for this I beleive, it goes back to valves (vacuum tubes).s Vavle pins are also numbered anticlockwise from the locatro because most valveholders were wired on the underside. Looked at from that side, the numbers go clockwise, which seems more natural. So perhaps it's acutally easier to wire ICs from the underside :-) As I said, this has never bothered me. Do you/ I jeust grab a suitable bit of prototpying board (cut to fit whatever case it's going to end up in if it's going in a case), roughtly position the IC sockets (leaving room for others if possible) and start soldering. I design as I go, based o nthe results of testing the bits I've buiit and got working. Again this has never been a problem for me. Oh come on. You hve to buy the ICs, the other cvmponets, sockets, etc no matter what method you use. Buying the SMD adapters is not a problem. And having all major devices socketed is very useful on a prototype (you can easilty re-use the chips, you can remove them and force signals high or low for testing and so on). -tony

Note I said nothing about the value of documeting the final design. I do beleive that that is _essential_. But there's no reason that the schematic has to be drawn before you start to solder... It shoudln't take that long. I do, which is why I have schematics of everything I've designed, notes how why I did certain things, and the like. Of course I include things that are useful when I need to repair it, like wire colours, pinouts of all internal connectors, which gate in an IC is used where, etc. I include all diagrams (including PSUs). The only exception is when something is so totally obvious from looking at the device that a schematic would be a wast of time. It depends on what it is, just as with programming. Sometimes I will 'desk check' a section before wiring it. Obviously I may need to calculate component values used in analogue sections of the circuity. But I don't need to desk-check the address and data buses between (say) a Z80 and an EPROM. I'll just wire those and doucment them in the final version. It depends on what I am coding or building, as I said. I always start by thinking about it :-). Sometimes I then start by coding/soldering, sometimes I need to plan some sections (but only some sections) more carefully. But just as I wouldn't write the full documetation for a program before Iwrote one line of code, nor would I draw the complete scheamtic before I started soldering. With programming I often need to write a routine and make sure it behaves correctly before I write more of the program. Same with hardware. I'll build a bit, make sure that works, before I build the next bit. SInce the SMD adapters are esseitnally PCBs with header pins soldered to them, why not just lay out said adapter PCBS and get them etched, Should be cheaper than buying them. If you're such a good designer that your PCBs work first tine, then great. If you don't mind waiting server days betweencoming up with the design and soldering the frist component then great again. But I am not like that. I need to test as I go. -tony