The magnetic switch is a wonder tool for designers who would like to turn a circuit on and off based on proximity. The Shiny Clutch and Aromatherapy Sachet in our book Switch Craft are two examples. However, buying the right magnetic switch can be tricky at times.
To cut a long story short: If you'd like to turn something OFF when the two halves of your switch are apart, buy the NORMALLY-OPEN (NO) type; to turn something ON when the two halves are apart, buy the NORMALLY-CLOSED (NC) type. This is the textbook definitions of NO and NC. For unknown reasons, there are some companies classifying their magnetic switches against the grain. Their NC switches turn things OFF when the two halves are apart, while NO does the opposite. This is why even some salespersons are confused as well. Therefore, before purchasing any magnetic switches, read the product descriptions carefully.
The readers of Switch Craft know that we recommend mini (low profile) NC switch for Shiny Clutch and Aromatherapy Sachet. To help you quickly locate the item, we searched the Web and found some options for you:
No introduction necessary.
(Catalog #) 55016278
It's a site for engineers and may look a bit intimidating. But it does provide the largest selection and the most detailed info. Click on "Datasheets" to view switch dimensions and technical drawings. We like these two pairs:
(Part #) CH406-ND + CH412-ND
(Part #) 59140-040-ND + 57140-000-ND
Minute Man Electronics
This is one of those contrarian places that label NO and NC in reverse. So look for "low profile normally open magnetic switch" on their site. Note the $20 minimum.
(Philmore #) 30-17054
If all this NO/NC talk makes your head spin, or you simply want a switch that can be reuse for a different type of project later, there is the 2-in-1 magnetic switch that combines NO and NC (its technical nomenclature is "SPDT"):
It's much easier to find regular-sized NO+NC type switch. If that is fine for your purposes, you may get one from the following sources:
You may have noticed that many security equipment vendors also sell magnetic switches. However, some of them do not supply detailed technical specs for their merchandises. Unless you are obsolutely sure about the item, or can return it easily, think twice before buying.
Since inventories change over time, the product numbers and links listed above may become obsolete sooner or later. Please leave us a comment if any links stop working. Should you find other stores selling mini magnetic switches, feel free to share it here too.