134 Chapter 4
fi rst thought. Apart from the switching differences, switches also come in different current
ratings; the higher the current capacity, the larger the physical switch. For the circuit
projects shown in this book, choose switches with the smallest current ratings available.
Here’s a very useful tip that I only found through experience: some small switches (the
toggle type) require a huge amount of force to toggle between positions. What this means
is that if you’ve got a very light plastic project case with this type of switch mounted on
the front panel, you will most likely tip over the case when you try to fl ip the switch. I
found this out the hard way! So choose small switches that have a very light toggle action.
A slight fl ick of your fi nger should fl ip the switch to the other position. Switches are quite
costly, and you can save yourself a bundle by not buying the wrong type.
Rotary switches are like super versions of the regular switch and are defi ned by poles and
ways. For example, a simple, one-pole, four-way switch will switch one input signal to
one of four outputs. Let’s say we had a two-pole, four-way switch. This switch has two
sets of independent contacts that can be coupled to one of four positions. Let’s say one
pole was used to switch a radio output to one of four speakers. To know which speaker
was being powered, the second set of contacts could be wired to four LED indicators,
marked as 1 to 4. Each LED would then light up, corresponding to its matching speaker.
This setup is shown in Figure 4.11.
4.1.5.3 Jack Plugs and Sockets
Audio connections are made much neater and easier with the use of miniature 1/8-inch
jack plug/jack socket combinations. If you’re using a jack plug, you’re going to need a
14
3(^21)
4
3
2
Figure 4.11 : One-pole, four-way rotary switch.