Wire Wrapping Power Distribution?

[cbmeeks]

My search skills aren't bringing back anything useful. Can't hardly search WW without some jewelry page coming up. :-/

Anyway, I'm starting to WW a computer but I'm curious on how you guys handle power distribution. I can't seem to find any information on this.

For example, I know you wan to use heavier gauge wire for power and ground. I was thinking of using my normal breadboard wire for power since it's thicker than the WW wire.

But wouldn't that mean soldering those pins together? I thought about perhaps using the VCC and GND pins as a way to tack down the WW sockets and then soldering point-to-point.

What are your recommendations?

Also, a separate question...if the WW sockets are to be put side-to-side in order to reduce distance, how are you getting decoupling caps in there? Some of these IC's have the power literally in the middle of the chip (I'm looking at you Propeller).

Thanks

[GARTHWILSON]

Do like a spider web, starting with a star with everything hooked directly into the center which has good bypassing, then connect the ICs around the center to each other.

With CMOS which takes very little power, wire resistance is not the enemy. The enemy is inductance, and the main way to minimize it, if you don't have a true ground plane (and no, copper pours and fills don't qualify, nor does nearby sheet metal that's grounded at one point), is to minimize the wire length. The wire size is not as important. 30AWG wire-wrap wire has 27nH of inductance per inch, and going up to 24AWG (twice the diameter, four times the cross-sectional area) only cuts it to 23nH, so not much difference!

In WW boards, you can put the decoupling cap.s under the ICs. Minimize the lead length.

Doing this, you won't have any trouble. See also our sticky topic, "Techniques for reliable high-speed digital circuits."

[cbmeeks]

Thanks for the response.

But, correct me if I'm wrong, I should *not* use the 30AWG WW wire for power and ground, right?

My SBC will be between 1-4MHz tops and most IC's are 5V. I will have a few legacy IC's like the TMS9918 and the AY-3-8910. I can't remember if those are NMOS or not.

Thanks.

[GARTHWILSON]

There is no problem with using 30AWG wire for power and ground, unless you're using a lot of power-hog 74xx TTL logic.  It would probably be fine even with 74LSxx, although there's no reason to use LS.  Use 74HC, 74HCT, 74AC, 74ACT, or other CMOS.

[Rob Finch]

I have used scrap 14 gauge house-wire for power busses in the past. Along with tons of capacitors.
I made my power busses 'F' shaped around the IC's, probably not the best thing to do, but it made wiring and placing busses easy.
I was working with only low speed, small size boards.

[cbmeeks]

I thought about doing something similar. Maybe running a couple power and ground lines across the board and tap into them when needed.

Did you keep the power lines insulated except where tapped into or were they bare wires?

I've seen people do both.

Thanks.