This Thing Called Wire Wrap

Whether you refer to it as a technique, a technology, or just plain old-fashioned, wire-wrapping is still valuable to know:

l Vhai arc the pros and cons of using wire-wrap technology? W e/A lei s check into it a little bit

Right from the start, you must breadboard a prototype of the "'want to be" new circuit to check the function and the expected performance. We folks with an engineering bac kground know that a computer simulation is not less expensive, easier to use, and so on. Using the LTreehaiuT design utilizing multisourced components requires a bread board to check the function. Expensive software packages, etc., just do not lend themselves io the ham radio community very well.

I have found over the years that a sood breadboard svsteui such as shown in Photo B is \ery helpful. Pushing components into the grid system performs some of the interconnects. The rest of the connections are made with #22 solid wire jumpers. ; his is an inexpensive and effective system of breadboard!ng. The system is reusable many times over You breadboard only small parts of the overall design just to verity the circuit function.

Now that vou have a 2ood-lookinu

* t? w schematic of the item you ¿ire designing sou can move on to the "wire-wrap"

portion of the circuit hoard that w ill go into the enclosure* If it is anticipated that 50 or more boards are to be made, such as a ham radio club project, then the finished schematic can be used to have an actual printed circuit board created. It will take about twice the board area if this is done, unless expensive multilayer boards are used. Remember, the computer software will require a computer-captured schematic which is cost I \ and time-consuming. The schematic will provide a point-to-point grid for all of the interconnect routes. Tliis is usuall\ called a net list. II everything works out OKT a PC board foil pattern will be made. This will be used to make a PC board, etched, holes drilled, tin plate over the copper foil, and finally the silk screen with component markings. The etched PC board is expensive and a lot of work. It is not justified unless many boards are required!

Now, the alternative is "wire-wrap" technology. It uses point-to-point wiring using sockets and AWG-3U wire-wraps. fl a mistake is made, a little "un wrapper" tool will remove the wire-wrap. Your local Radio Shack store has a wrapper/unwrapper tool,

Photo A* Ct \f-I perforated PC board and machined pin wine-wrop sockets. 32 73 Amateur Radio Today * August 2002

#RS-276-1570A, which sells for about $8. The tool also has a wire stripper stored in the handle. A very nice tool for the price.

You might now ask, "Where do I get the TC sockets, perforated hoards, and AWG-30 Kyiiar wire?"

There are several companies that supply these items, such as Jameco Electronics, Mouser Electronics, and Hosi'cll Electronics. Make sure that the IC sockets are the rnachined-pin-type round pins so that the round wire leads of components can be accommodated, (Normally, a square pin is used for wire-wrapping sockets. The objective of the square pins is to create a gas-tight joint, Wire is pulled tight against iftefgur corners of the pin to produce a reliable and permanent joint. The machined-pin wire-wrap pins on the DIP sockets are like ALL wire-wrap pinsJj square with four corners. The point the author is making is that a normal socket, not machine-pinned, will not accommodate a round wire such as is on passive components like resistors, capacitors, and diodes. Therefore, a DIP IC socket must have a machined pin, All DIP IC sockets used in wire-wrap have square lower pin construction. Key word; machine pins. — ed,)

Either the two- or three-level gold or nickel pins are suitable. When wiring a board full of sockets, it is recommended that the ground and supply wire leads be put into place first using black and red wires respectively. The interconnects can then he green or white wire. Several colors are available, so use the colors you prefer. The spools of wire are usually available in 100- and 1000-ft. spools. The cost is typically less than 3 cents per foot.

After a few projects are done, your confidence and expertise wili improve to the point where any project will not be too hard. You will then want to move up to the high performance end of things to make everything easier and faster.

This of course requires some tools which are more expensive. The investment can generally be recouped in one good-sized project which would normally require an etched PC board. See Photo C for a look at some of the tools which arc used. Noticc the 120 VAC wire-wrap gun and professional strippers. These arc the high performance tools I mentioned. The gun shown is one that I picked up at a hamfest flea market for $15. li came in its original package with a bit and sleeve. Ready to go! The same model's newr cost is about $200, plus the $20 for a sleeve and bit. Still not bad, considering! The new tools are available from Mouse r Electronics and others should you need to purchase new items. I purchased 1000-ft. spools of Kynar wire from Jameco Electronics al under $30 per spool. The sockets usually cost between 35 cents and $1.25 each for DIP-14, 16, 24. Either gold- or silver-plated sockets work equally well. The gold show?s up a little better against the grid PC board for us old folks with bifocals. Bargains can he found, such as with Hosfelt Electronics, where DIP WW sockets can be had at 35 to 50 cents each.

1 purchased over 100 DIP-14 and

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