On Sat, 9 Jul 2011 05:19:01 -0600 Ed Hartnett <edwardjameshartn...@gmail.com> wrote:
> On Mon, Jul 4, 2011 at 7:46 AM, DJ Delorie <d...@delorie.com> wrote: > > > > > > I am trying to make my first PCB and I have selected a > > > super-simple > > circuit > > > to start with, a 555 astable circuit. It's a single-sided board, > > > and I'm going to etch it myself - something I've always wanted to > > > try. > > > > > > But what footprints do I use for the GND and VCC connections? I > > > guess I would just like these to be two pads on the PCB. Is there > > > a way to tell gschem this? Or do I just manually make that change > > > in the pcb program? > > > > Usually, you would add one two-pin connector, or two one-pin > > connectors, for the power connection. There are a range of > > footprints available for this - if you just want to solder wires to > > it, HEADER2_1 is sufficient - it's just two pins on 0.1" centers. > > > > Would this be done in gschem? Or in pcb? > > In gschem I have a symbol for gnd, and there is no footprint > associated with it. There is another symbol for +5 V. Do I add a > connector on gschem and use it instead of then GND/5V symbols? Or do > I associate a footprint of HEADER2_1 with each of them? Or with one > of them? I think Kai-Martin probably answered this pretty thoroughly, but I'll comment that, like you, I once wanted to add two plain old surface mount pads to which I could solder my power/ground supply wires. You correctly noted that GND/+5V symbols don't have a footprint associated. These “power rail” symbols, like the input/output pin symbols (input-2.sym, etc.), are schematic conveniences only. You could remove them and instead connect all nodes with actual net lines instead, but that is often very messy. The power rail and I/O pin make schematics cleaner. What you want is to use is either (1) use connector2-1.sym, and then assign it a 2-pin footprint like “JUMPER2” (2-pin SIP, 100 mil pitch through-hole header). Then connect pin 1 of the connector to your ground net and pin 2 to your power net (or vice-versa). If you want surface-mount pads, you can assign the connector component a 2-pin SMD footprint like “RESC4532M”. or if you want to be able to separately place the power and ground connections on the PCB layout: (2) insert two one-pin symbols (e.g., terminal-1.sym connector1-2.sym, but note that these are “heavy” symbols and you need to change the footprint unless you want the default though-hole pin footprint). Connect one symbol to your ground net and one to your power rail net. Assign the appropriate footprint--for a through-hole footprint, use “JUMPER1”, “CONNECTOR 1 1”, or “SIP1N”; for a surface-mount footprint, use a test-pad symbol or other single-pad SMD footprint (look on gedasymbols.org; AFAIK the default pcb footprint library doesn't have any single-pad SMD footprints). Tip: If you use a 2-pin through-hole JUMPER2 footprint, you can solder a 2-pin header from a ubiquitous single-row breakaway header (100 mil) and then have a detachable power supply connection. I have found the low-cost Molex KK-100 series kit (see [1] below) invaluable for all sorts of connections like this. With a bit of practice, you will be able to quickly made a wide variety of cables from 1 to 10+ pins. I use bits of ribbon cable to make most signal connectors because it's very convenient and looks tidy when you're done. Regards, Colin References [1] Molex KK-100 Connector Kit With premium crimp tool (I highly recommend this option): Molex Part #: 76650-0009 Mouser link: http://www.mouser.com/ProductDetail/Molex/76650-0009/?qs=sGAEpiMZZMtsLRyDR9nM1%2ffCLkgKsWdRr36mItq8jVo%3d With basic crimp tool: Molex Part #: 76650-0007 Mouser link: http://www.mouser.com/ProductDetail/Molex/76650-0007/?qs=sGAEpiMZZMtsLRyDR9nM1%2ffCLkgKsWdRSyrCqTUdKBE%3d _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user