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tutorials, and useful design techniques.

BREADBOARDING

by Stuart Ball

Start ý Grounding ý Placing Copper Strips ý Power Wiring and Supply Bypassing ý Lead Wiring ý Test Points ý Surface-Mount Parts ý Other Tips ý Putting It All Together ý Other Techniques ý Sources and PDF

OTHER TECHNIQUES

Wire-wrap is a similar prototyping technique, using IC sockets with long pins and wrapping stripped wire-wrap wire around the pins. Wire-wrap can be used with the copper ground strip technique, but the wire-wrap sockets are relatively expensive. They often cost more than the ICs themselves!

Wire-wrap has an added disadvantage in that the long wire-wrap pins make it impossible to do any kind of low-profile mounting. Any wire-wrap project will have a project board with a thickness of at least 1ý. In addition, many components (such as connectors) are not available in wire-wrap versions.

Many experimenters make their own circuit boards for projects. There are drawbacks to these methods. The simplest way to make a circuit board is to manually draw the circuit pattern on a blank PC board with an etch resist pen or dry-transfer patterns (both available at Radio Shack). The problems with this approach are circuit density, registration, through-board connections, and circuit quality.

First of all, you can only get so dense with those traces, especially because the circuit layers have to be shared with the power and ground connections. There is no way to get more than two layers with any manual process

Secondly, a double-sided board is difficult to keep registered, unless you drill all the holes first and place the pads/traces second.

Also, any connection that has to be made through the board requires that a wire be run through the hole and soldered on both sides. Component leads with traces connected to the top and bottom pads have to be soldered on both sides of the board to make the connection.

And finally, whether using an etch-resist pen or dry-transfer resist, it is difficult to make the board without some breaks in the resist. These result in open traces that have to be located and fixed.

Some experimenters use photoetching, which usually eliminates the open-trace problem but still leaves all the others.

Clearly the best way to make printed circuit boards is to use a CAD package and send the resulting Gerber files to a board shop. This takes care of registration, through-hole plating, and allows multiple layers to be used. The drawback, of course, is the cost. Most circuit board houses have high initial setup fees and a minimum order requirement. However, there are services on the Internet that cater specifically to the hobbyist by reducing the setup fees and providing a bare-bones two-layer process.

Although you wouldnýt want to hand wire a 500-MHz Pentium processor, the copper-tape and wire method of prototyping allows you to experiment with higher speed devices and parts than traditional prototyping techniques allow.

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