Selecting the Right Switches for Your Project

The range of available switches and sensors can be overwhelming, especially for amateur makers. There is an incredibly wide array of hand switches, motion- and light-actuated switches, vibration- and acceleration-actuated switches, and other switch types readily available on the market.  

Despite this variety, however, all switches are basically on-off mechanisms that allow the flow of electrons into part of a circuit when a condition is met.  This means that for any given project, several dozens of switch types may technically work for a certain purpose. However, not all switches will necessarily be the best choice. Imagine if elevator buttons were to be replaced with dip switches that require tweezers, or if refrigerator lights had to be manually activated each time you needed them.  The selection of the right switch type is thus, a central part of designing the user experience for a given project.

Here are some areas to consider to help you purchase the right switch for your project:

Performance rating

Each switch will typically be rated for two areas: voltage and current. It’s important that any switches you use will not be subjected to voltage and current greater than what they are rated for. You will typically find the ratings for switches printed on each piece.

The type of switches that would work for a low voltage circuit may not be the best choice for one needed for a high voltage circuit. Using a switch that does not meet a safe voltage requirement can lead not only to a catastrophic failure of your project, but it also poses a possible fire hazard as well.  Likewise, the using a switch that cannot handle the current in the circuit can also result in failure of the project by causing contact points to weld together.

Robustness

You don’t need to be a maker to have noticed that not all switches are built the same. Two different switches of the same type and performance ratings can have drastically different levels of build quality. Both types may perform exactly as needed for the first thousand cycles, but the inferior one will generally give out much sooner.

If you intend your project to last, it’s prudent to invest in switches that have been tested to function for more cycles. These switches will often be built from sturdier materials and have features such as seals and covers to resist premature wear and tear from regular use and oxidation. Use these more robust switches for anything “mission-critical.”

Ergonomics

Consider the normal conditions under which your project will be used.  In the vast majority of cases, operators may only be able to use their two hands, and possibly one of both feet, if we consider foot switches. If limbs need to be free after actuation, a latching switch should be considered.  If the project is meant to work non-invasively in the background, switches that rely on automation such as proximity, temperature, liquid level, and other types of switches may be considered.

Sometimes, the best decision may be not adding more switches than is strictly needed. You also have to consider that additional switches and functions may actually serve to distract from the main purpose of your project and that added complexity will present possible critical failure points. If a specific function of the device only needs to be accessed infrequently, an internal dip switch that can only be accessed from the inside might be necessary.

Environmental factors

Heat, dust, and humidity can wreak havoc on the longevity of any project. Heat may cause eventual warping of switch components, resulting in their premature failure. Dust can prevent proper connections between contact points, and can even corrode them, possibly causing arcing and short circuits or a total loss of function. Humidity can likewise cause corrosion and short circuits on switches and other components as well.

In cases where your project may be exposed to those factors, sealed switches can be acquired. The tradeoff would be a higher initial cost. These sealed switches may not always be necessary, however, and traditional types may more than suffice for most projects.

Size

To put it simply, larger switches are harder to miss. For instance, fire alarms can be made much smaller. Their specific function, however, demands that they are easily seen and actuated.  Switch size also makes a difference in user experience. How much harder is it to type on a regular-sized keyboard with regular-sized keys compared to one half as large?

The tradeoff of larger switches, however, is that they often leave a larger footprint. This means less space for other switches and less space for activating other features of your project. Larger switches will also consume more space in your enclosure, using up real estate that could otherwise be dedicated to other components and making it hard to keep the project a practical size. Thus, switches should only be as large as they need to be.

Cost

If we were only making projects for ourselves and money were no object, there would be no reason to bring this factor into consideration. In a production setting, however, the costs of each switch have a way of compounding, driving up the cost of your overhead, often for no real difference in performance.  

While we all want to get switches that improve a device’s longevity, safety, and performance, you will not necessarily get there by choosing only expensive components, as many factors including marketing, perception, tariffs, and labor costs that have no bearing on component quality can also drive the cost of switches up. It’s also worth noting that not all expensive switches are necessarily better, as modern fabrication methods have greatly reduced the cost of many components without sacrificing real quality. For any project that needs to be brought to scale, try to assess switches by their actual performance and value rather than by specious metrics such as price or country of origin.