Basic electronic components don't get much simpler than a switch, but there are a startling assortment of different switches out there, for every possbile need.
schematic symbol for a single pole, single throw (SPST) toggle switch
schematic symbol for a single pole, single throw (SPST) momentary switch
It even looks like a push-button!
A "normally closed" switch does just the opposite. When the switch is just sitting idle, electricity flows through it. When you actuate the switch, the flow stops.
schematic symbol for a normally closed momentary switch (SPST) switch
schematic symbol for a single pole, double throw (SPDT) switch
schematic symbol for a single pole, triple throw (SPTT) switch
Most switches with over two throws are
rotary switches.
When there is more than one throw, the switch usucally breaks the first connection and then makes the other connection. There is also an option for "make before break", where the new connection is established before the old one is broken.
A "double pole, single throw" switch is essentially two simple switches packaged together, so that when you activate the mechanism, both switches are activated.
schematic symbol for a double pole, single throw (DPST) switch
A "toggle switch" has a lever protruding from the front. The lever is sometimes described as "bat handle", because it sometimes looks like a little baseball bat. Toggle switches tend to have a very positive feel and look to them: they are designed so you can easily tell if the switch is on or off.
This page from the
All Electronics
catalog (#203, Spring 2003) shows some toggle switches.
A "snap switch" has an internal pivot mechanism that makes sure that the switch is absolutely on or off. They often make a little "click" noise as the switch. The external actuator might be a little button that is pushed, or a stub that is rotated.
One of the most famous makers of snap switches is "Microswitch", to the point that some folks use the name "Microswitch" when they mean "snap action switch".
This page from the
All Electronics
catalog (#203, Spring 2003) shows some snap switches.
A "slide switch" has a slot on the fase, with a nub that can be pushed from one side to the other. Slide switches tend to be inexpensive. The chief drawback of slide switches is that it is possible to push the nub partway, leaving your circuit in an indeterminate state: is it on, off, or part on and part off?
This page from the
All Electronics
catalog (#203, Spring 2003) shows some slide switches.
A "rocker switch" has a pivot and an actuator that moves like a playground see-saw: you push one side down and the other side goes up; push the up side down and the other side goes up.
This page from the
All Electronics
catalog (#203, Spring 2003) shows some rocker switches.
A "push button switch" has an actuator that sticks out of the front: push it in to actuate the switch.
Classically, push button switches are momentary action: they work as long as the button is pressed. Some switches go on with one push and take another push to turn off.
This page from the
All Electronics
catalog (#203, Spring 2003) shows some push button switches.
A "rotary switch" is actuated by twisting the protruding knob or shaft.
Although rotary switches can be simple, they are commonly employed in situations where the switch wants to have more than two settings.
This page from the
All Electronics
catalog (#203, Spring 2003) shows some rotary switches.
A "reed switch" is actuated by the nearby presence of a magnet. This makes them handy for things like burgular alarms.
This page from the
All Electronics
catalog (#203, Spring 2003) shows some reed switches.
What type of mechanical action activates the switch? Do you press it, or slide a tab from one side to the other? Does it have a toggle or a rocker? Perhaps you twist it.
Here are some actuation methods:
This indicates how heavy a load the relay can control.
If you can't find exactly what you want, you can use a switch with a higher rating.
There are many kinds of switches, because there are various gadgets that might need to be controlled. The contact geometry indicates how many poles there are, and how they open and close. Some examples are: single-pole single-throw; single-pole double-throw; and double-pole double-throw.
If you can't find exactly what you need, you can use something with more poles, and simply ignore the unused contacts.
Look in stores that cater to electronic experimenters, such as:
Thank you for visiting. Your comments are welcome.
![[back]](../_aCommon/l_hand.gif){kind=small}
. . .
![[paper and pen]](../_aCommon/an-feather.gif){kind=small}
. . .
![[tip jar]](../_aCommon/icon_TipJar.gif){kind=icon}