zaft@azstarnet.com

Since I've been in the business of proof-of-concept prototyping for the past 25 years, I thought I'd wait until everyone else weighs in on this matter. I have found very few wirewrap cards capable of distributing power properly, so I have made my own wherever practical. The boards I make have a continuous ground plane on the wiring side of the board and a continuous Vcc plane on the component side, with a ground strip around the exposed edges of the board, away ground strip on both sides is available at each edge. This facilitates ground reference attachment for 'scope and logic analyzer. The holes are plated through and the board is coated with a dry-film solder mask, thereby facilitating the use of bare-wire analog circuit construction where it's needed. I've run fairly large synchronous circuits on a board of this type, with as many as 250 bipolar flipflops toggling at more or less the same time, i.e. from the same, albeit separately buffered, clock edge, without harmful effects, all the while monitoring the power<=>ground noise to be <100mv. The trick, of course, is that the attachment to the ground and power plane is normally accomplished by means of a soldered-on capacitor of relatively small value, typically 0.01 microfarad. Since one lead of a bypass capacitor is attached to the power pin of each IC, the other can be attached very near the capacitor by soldering it directly to the ground plane. So long as one keeps the leads shorter than about 1mm, the maximal benefit from bypass will be obtained. I still use boards of this type, albeit seldom with the solder mask, since I buy the big "colander" panels at RadioShack.com and cut them to fit. I still isolate the outer edges of the continuous power plane on the top of the board by relieving it from the main plane by means of a dremel too with a saw blade, and then connect the edges to ground with a solder bridge wherever it's convenient. That way I can still attach probe grounds wherever I need. There are few ways, short of having them made up, which is what I did, to get decent wire-wrap boards that will accomodate the connectors and IC packages you'll need. The RS.com store located here in Denver has large panels of this ground and power plane equipped perf board with plated-through holes, for about $100, which is plenty, but the boards are big enough to warrant it. regards, Dick ----- Original Message ----- From: "Gordon Zaft" &lt;zaft(a)azstarnet.com&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Monday, October 22, 2001 3:21 PM Subject: Re: OT: power & ground for wirewrap boards