All about Switches
Posted by Rohan on Sunday, June 29, 2014 with No comments
When you flip a toggle switch it connects the center terminal with one of the outer terminals. Flip the switch back, and it connects the center terminal with the other outer terminal, as shown in Figure below:
The center terminal is called the pole of the switch. Because you can flip, or throw, this switch to make two possible connections, it is called a double-throw switch. Some switches are on/off, meaning that if you throw them in one direction they make a contact, but in the other direction, they make no contact at all. Most of the light switches in your house are like this. They are known as single-throw switches. A single-pole, single-throw switch is abbreviated SPST.
Some switches have two entirely separate poles, so you can make two separate connections simultaneously when you flip the switch. These are called double-pole switches. Check the photographs below
SPARKING :
When you make and break an electrical connection, it tends to create a spark. Sparking is bad for switch contacts. It eats them until the switch doesn’t make a reliable connection anymore. For this reason, you must use a switch that is appropriate for the voltage and amperage that you are dealing with. Electronic circuits generally are low-current, and low-voltage, so you can use almost any switch, but if you are switching a motor, it will tend to suck an initial surge of cur- rent that is at least double the rating of the motor when it is running constantly. You should probably use a 4-amp switch to turn a 2-amp motor on and off.
Checking a switch :
You can use your meter to check a switch. Doing this helps you find out which contacts are connected when you turn a switch one way or the other.
Set your meter to measure ohms, and touch the probes to the switch terminals while you work the switch. This is a hassle, though, because you have to wait while the meter makes an accurate measurement. When you just want to know whether there is a connection, your meter has a "continuity tester" setting. It beeps if it finds a connection, and stays silent if it doesn’t.
Some switches have two entirely separate poles, so you can make two separate connections simultaneously when you flip the switch. These are called double-pole switches. Check the photographs below
SPARKING :
When you make and break an electrical connection, it tends to create a spark. Sparking is bad for switch contacts. It eats them until the switch doesn’t make a reliable connection anymore. For this reason, you must use a switch that is appropriate for the voltage and amperage that you are dealing with. Electronic circuits generally are low-current, and low-voltage, so you can use almost any switch, but if you are switching a motor, it will tend to suck an initial surge of cur- rent that is at least double the rating of the motor when it is running constantly. You should probably use a 4-amp switch to turn a 2-amp motor on and off.
Checking a switch :
You can use your meter to check a switch. Doing this helps you find out which contacts are connected when you turn a switch one way or the other.
Set your meter to measure ohms, and touch the probes to the switch terminals while you work the switch. This is a hassle, though, because you have to wait while the meter makes an accurate measurement. When you just want to know whether there is a connection, your meter has a "continuity tester" setting. It beeps if it finds a connection, and stays silent if it doesn’t.
Categories: BasicElectronics
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