West Florida Components

A rotary switch is a kind of switch that has a rotating shaft attached to a terminal. That terminal is able to make or break a connection to one (or more) other terminals. Rotary switches may feature different switch positions that can be set by rotating the switch spindle in one or another direction. Some common examples where a rotary switch might be used is in a multi-speed fan or as a band selector on multi-band radios. Until the early 1970’s, rotary switches were used as channel selectors on TV receivers.

In general, rotary switches can be found where ever there is a need to control a large number of circuits covering a range of currents, voltages and power requirements. Currently, you will find rotary switches in these applications:

1. medical equipment
2. computers
3. industrial controls
4. instrumentation
5. communications equipment
6. aircraft equipment

The construction and design of a rotary switch is centered around the center rotor. The rotor has a contact arm that projects out from its surface. Around the rotor are an array of terminals. These serve as the contact for the arm, or spoke. Since the switch has multiple layers, each layer permits the use of an additional pole. There is also a detent mechanism which will click into place as the switch is turned from one active position to another. The contact / sensor system and detent mechanism determine the number of possible switching combinations.

Above is an example of a Grayhill military rotary switch. You can see it has 5 decks. Each deck has 1 pole. Each pole has 9 positions.

This is an example of a 16 position rotary switch assembly 1-435304-1. This rotary switch assembly has a bar handle. It is a single pole but has 16 positions.

Although it is often one of the last components considered, selecting the correct switch is important when designing electronic equipment. Designers must be aware of the various options available in order to choose the most appropriate switch for any given application.
The procedure of selecting the correct switch can be summarized this way:

• The requirements of the end user should be given consideration first
• The engineering aspects like load, contact materials, terminal type, voltage, circuit type, mounting etc should be studied
• Next the type of actuator should be decided
• Standards like RoHS and similar government regulations must be complied with as well
• Lastly, the switch chosen should be able to stand up to the rigors of the application. Environmental factors must be considered

When choosing a switch, you can ensure that the most appropriate switch is selected for the job if you take these factors into consideration.

We’ve been selling a lot of this one particular switch - it’s called a long travel tact switch; manufactured by ALPS.

Here are some of the features of this switch:
– Dimensions: 8mm x 8mm
– Suitable for automotive applications due to its high operational force
– Malfunctions are prevented due to it having a longer travel than most conventional tact switches
– Easily mounted on a PC board with snap in leads
– Some of the output terminals can be used as jumper leads which makes the circuit arrangement simple

Here are some other uses:
– automotive electronic equipment
– communication devices
– measuring instruments

These switches are available right now - they have been priced lower than any other distributors.

Be sure to check them out next time you need a 12V tact switch!