The function of switching a circuit on or off can be accomplished both mechanical and/or electronically in many different ways with many different types of devices. Here we will look at a few options for your next project.
Whether it be a pushbutton, toggle, rotary, slide, membrane or any other contact type manual switch one thing is common. That is that all the current and voltage in the circuit flows thru switch, so it is important to size the switch correctly. Analyze your input and your load and make sure the switch is rated for the circuits voltage and current. Markings can typically be found on the switch body.
By applying a relatively small voltage to a coil, you can switch a larger voltage with the relay’s contactor points. Relays come in all shapes and sizes, so again be sure to select a device with appropriate Voltage and Current ratings. With this device you also need a secondary power source to energize the coil and a switch to control that power source. Size the secondary power source to the coil requirements of your relay device. The relay circuit requires more parts and more work but the advantage here is that we have separated the high voltage circuit from the user interface switch device.
As great as relays can be for many applications the fact is that, being an electro-mechanical device, they do wear out. Typically life span in cycles will be listed on the device datasheet. A calculation such as,
“On average I assume that I will be turning on this vac three times a day for 20 years” 3 X 365 X 20 = 21,900 cycles
will guide your selection process.
If your application requires faster or more frequent cycling, then it is worth looking into solid state devices. Amazingly enough, this smart fellow (http://en.wikipedia.org/wiki/Roy_Mankovitz) invented the Solid State Relay.
Sticking (pun intended) to the theme of electromagnets and magnetic coupling. The Reed Switch and Hall Effect Sensor can further isolate the user from the device voltage. Reed switches, which are basically the output section of a relay do share the limited life cycle characteristic with their cousin, the relay. Hall effect switches on the other hand, although harder to implement have a nearly infinite lifespan.
I hope this gives you some ideas for how to reliably control your shop equipment. If you have any questions about any of these devices, please leave a comment below or use the contact page to submit them.