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Sensing and Control for hobbyists and schools: Connection issues



If you are a beginner, stick to low voltage DC stuff... i.e. less than 15 volts.

This page, and the pages it links to, address two aspects of connecting. Not only are the actual wires you will use discussed, but also different means of connecting between the controlling PC and the sensors and actuators are explored.

Using 1-Wire (also known as MicroLan) technology.
Using LANs or the internet.
Using a parallel port.
Using using a serial port.
Using using a USB port.
Using X-10 technology.

General issues (concerning wires and connectors)...

"Cat-5" cable will suit many control and sensing projects for schools any hobbyists. I saw a 100' roll at my local hardware store for $16. There is a cheaper alternative, apparently just about as good, called "Cat-3"... but when I found some of that it was $14.... and it only has 4 conductors, whereas Cat-5 has 8. My 2 cents worth says that the extra two conductors are certainly worth the extra 2 cents per foot. You don't have to use them!

Cables come in single and multi-stranded variations. In other words, each "wire" in the cable may be a solid copper strand, or made up of many very fine strands. The former is usually cheaper, and the latter endures repeated flexing better.

Even for a cable of a given conductor count and conductor type/ count, there are variations. Often, there is an "exterior" grade, but the interior grade isn't going to melt the first time it gets damp. There is a "plenum" or "riser" grade. If you are going to run your cable through air ducts, then you probably SHOULD go for this: If ever you have a fire, the plastics used give off less poisonous fumes into the air going through the ducts... to YOU.

Connectors: If you are using RJ-11s, they will be convenient, but they may not serve too well in outdoor applications, e.g. weather stations.... even if they are protected from direct rain. (RJ-11: The roughly 1cm x 1 cm plug/ socket pair used for US telephone devices, and the modem end of most modems. 4 conductors.)

If you want to use them anyway, don't be tempted to use Vaseline to protect them. Several Weatherlist readers reported all sorts of problems. (There's more about the Weather list at my 1-Wire Weather Stations page.) For sealing RJ-11's against the weather, the best answer seems to be silicone bath sealer. An even better answer is to solder wires to PCBs if they are going to be outdoors.... and seal the joint! (A film of condensation over an unsealed circuit can do lots of things... none of them helpful!) Many, many troublesome systems have become reliable after the simple effort of a good dose of "is every connection sound?" housekeeping.

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Other projects

This is just one of the guides I have published on the net. Please visit any of the following that relate to interests you have....

Delphi Tutorials
Pascal programming tutorials
Electronics for hobbyists and schools
Main Home Page

Here is how you can contact this page's author, Tom Boyd.

Index of sensing and control pages (From there you can also go to other help from the editor of this page.)

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