On Wed, Mar 23, 2011 at 08:06:28AM -0400, Olin Lathrop wrote: > 'William Chops" Westfield ' > It depends. Couple bucks for blank copper clad. Couple bucks for > > etchant. Significant bucks for the high-grade ink cartridge (for > > direct to PCB printing) (which may or may not dry up between PCBs (I > > hate inkjets!)) or a couple bucks for special transfer paper or > > transparency paper. Couple bucks for drill bits. Couple bucks for > > tool to cut the PCB material. Moderate amount for an inkjet printer > > to modify, or for a laminator, or for an iron, or for a contact > > exposure frame. Couple buck for other chemicals, sandpaper, etc. >=20 Olin I figured you would wander by this thread eventually. I'll take a crack at it. This is purely from a hobby perspective. So there should be no professional attribution applied to it. > And not having plated holes, decent design rules like at least 8/8 mils > needed for modern packages, no silkscreen, no soldermask. When you reall= y > add it up, you're probably paying yourself less than $10/hour to make you= r > own boards. Since it's a hobby, neither making money, or trying to attribute money to the time applies. Hobbyist do the job because it's fun for them, not work. > If you're really a hobbyist and claiming your time is worth little, then = why > is fast turnaround so important? Simple: because a hobbyist wants to see the results ASAP. This isn't consulting where there's other work to do while waiting around (which you point out below). Whatever project a hobbyist is working on is the sole focus of the hobby at the time. So waiting around is neither productive nor fun. > I do this professionally where time=3Dmoney, > and 1 1/2 weeks to get the boards back is rarely a problem. That gives y= ou > just about the right time to put the BOM together, order parts without ex= tra > fast shipping, and have everything arrive at about the same time. Meanwh= ile > you work on other projects. Surely you've got something else useful to d= o > while you're waiting for the boards and parts to show up? But this isn't a profession, so none of that applies. There isn't any other project to work on. Parts are in the junk box. Production is a one off. So getting it out the way as quickly as possible, and getting the instant gratification you alluded to below is in fact the objective of the hobby. >=20 > If you're constantly finding yourself doing quick turns of PCBs internall= y, > then you should examine your proceedures. The instant gratification of > quick turn may feel good, but I strongly suspect it doesn't make business > sense in most situations. A place that does that regularly probably has > immature engineers that don't know how to get the most out of each protot= ype > or are a little OCD in that they want to spin the board the moment a cut = or > jumper is added to the existing one. All of these are professional prospectives, and make perfect sense in that venue because the objective is to maximize the use of time to leverage it to make money. But with a hobby, it's for fun. An idea pops into the hoobyist head, and the focus is to realize it ASAP. First crack is usually on a breadboard, do some noodling to get an idea of how to put it together. While this is fine for quick and dirty development, eventually the late alpha or early beta needs to be transferred to permanent media. This is where the quick turnaround comes in. Note there's no BOM to deal with, because all the parts needed for the project are now on the B&D breadboard prototype. There are other ways to do it such as this through hole protoboard: http://www.dipmicro.com/store/PCB-PK28 or others like it. Works for the core controller and its associated electronics. But then it's back to point to point wiring for the project specific stuff. As a hobbyist, neither the process of waiting around for the project to come together, nor the tedious process of assembly are very gratifying. For a real job, for real money, it's work and you suck it up. But I already have a real job, with real work (a lot of it tedious). So if I'm doing something fun, the last thing I want is for it to look like work. In my ideal hobby world, a project would consist of using a tool like Eagle or Kicad to capture the project schematic, produce the board and a solder stencil mask from the design, etch both (board on PCB, stencil mask on brass or steel), slather the solder paste via the mask, populate, then grill the components to the board using a hot plate. Two hours tops from start to finish. >=20 > I find we usually do 3 PCB versions, sometimes 2, for most project. The > first is usually a bench test unit that ignores the final mechanicals. > Parts are deliberately spaced out with extra test pads, LEDs, and the lik= e > added to aid debugging and possible modifications. Usually this includes > the largest PIC of the subfamily. Most of the development is done with t= his > board. The second version is designed to be the shippable product. Now = we > get rid of extraneous LEDs, use the right size PIC which we know since th= e > firmware is mostly working, add the inevitable little things to accomodat= e > spec changes, etc. Often the customer will change some specs after this > board because this is the first time others in the company get to see ful= l > mockup units. We let this settle out a bit and the third version is usua= lly > the first production version. Respins are not that expensive if you mana= ge > the process properly and especially when you plan on them up front. Sounds like a great professional job. But why would a hobbyist who needs exactly one of these go through this process? Only the first version is necessary because it's not for sale. The hobby objective is not to build a sellable product. The objective is to come up with a permanent realization of an idea with as little hassle as possible, as quickly as possible. Cost effective would be nice too, as long as it doesn't create a hassle. The true difference between a professional and a hobbyist is that a professional is paid to overcome project obstacles in a timely fashion. With a hobbyist, obsticles kills projects, because the project is a realization of an idea or a dream that has no cost basis attached to it. BTW Olin, what do you do for a hobby? BAJ --=20 Byron A. Jeff Department Chair: IT/CS/CNET College of Information and Mathematical Sciences Clayton State University http://cims.clayton.edu/bjeff --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .