Choosing Tactile Switches for Your Electronic Applications A tact switch is a type of switch that is used every day, but hardly ever seen. Hidden under every key of a computer keyboard, the tactile switch is small and thin, but features high reliability to ensure it will operate for years or even decades. Tactile switches are small electromechanical devices that are designed to be mounted onto a printed circuit board (PCB). These products are compact with a low profile, meaning these do not rise high above the PCB, a vital attribute when considering the keyboards use for slim devices such as notebook computers. Considering that space inside a keyboard is limited, the slim design means that tactile switches must compete with batteries, screens, and other components. To solve this, tactile switches are designed to be positioned side-by-side in a compact array, an attribute important for a keyboard. The improvements made to the performance of smartphones and tablet computers make them a viable alternative to traditional computers. Tactile switches are small and convenient, suitable for touchscreens that utilize capacitive technology, which harness the electrical properties of the human body to function. For example, when a finger touches the screen, a tiny electrical charge is drawn to the point of contact, and the screen becomes a functioning capacitor. This in turn is detected as a push of a button. Touchscreens are very thin, especially as there are no mechanical moving parts, and the technology is constantly improving to make them thinner still. With the constant improvement of touchscreens, why are manufacturers not making a computer keyboard using capacitive technology? The answer to that question is the feel of keyboard keys, sometimes described using the word haptics. Despite the capabilities of touchscreens, these are hard and unforgiving. While there are many advantages of this smooth, flat surface - these are easy to clean and provide an effective compliment for high definition displays - these provide no feedback to the user, showing why the tactile switch is so useful. The tactile switch is a mechanical device. The force required to depress the switch, the distance it travels, and the spring as it returns once released all contribute to the “feel” of the switch. The most obvious example of how the haptics of a tactile switch affects the functioning of a device can be found in the computer keyboard discussed earlier. Anyone who uses a computer frequently will know that the movement of the keys on a keyboard can have a real impact on its ease of use, which in turn affects factors including typing speed and operator fatigue. It is the tactile switch that gives the keyboard its feel and familiar clicking noise when a key is depressed. Offering a combination of low profile, high reliability, and mechanical feedback, tactile switches are suitable for use in many applications. The market for wearable technology is growing quickly, driven by the huge adoption of smartphones and the expansion of high-speed internet services. Building sophisticated electronics into garments or devices that are designed to be worn requires components such as tactile switches that are not bulky or heavy, creating a design opportunity for wearable technology applications that require innovative visual indicators or control panels. For example, a soldier wearing smart body armour in a tactical environment or a paramedic using body-mounted cameras might find it unwise to display unwanted light. In situations like these, tactile switches provide the user with both ease of use and a physical indication of correct operation. Manufacturers tactile switches available for variety of uses, When combined with the huge array of keys and actuators that are available, the tactile represents one of the most versatile switches on the market today. Why is Micro Switch called a micro switch Micro switch is an electric switch (patented in 1932) that is actuated by very little physical force. Switching happens at specific positions of the actuator (not like other switches). Relatively small movement at the actuator button produces a relatively large movement at the electrical contacts, which occurs at high speed (regardless of the speed of actuation). Typical durability is from 1 to 10 millions of cycles. This durability is a natural consequence of the design. Micro switches are not operated by person; it is always some moving part of the equipment. Common applications are detection (e.g. jammed paper in photocopier, the presence of material or product). Other application can be a limit switch (for control of machine tools) or door switch (e.g. fridge). What is important when using micro switches? First of all, load size and type. Some types of load have much higher inrush current. E.g. relay has 5 times higher inrush current than nominal, motor 10 times, incandescent lamp 15 times and solenoid even 20 times. On the other hand, for switching small loads, do not use a micro switch for high currents. We recommend using micro switch with gold plated contacts. For harsh environment (dust and moisture), please use safety micro switch with higher IP rating (up to IP67). We recommend applying a contact protective circuit to extend contact durability, prevent noise, and suppress the generation of carbide or nitric acid due to arc. The use of a contact protective circuit may delay the response time of the load. Examples of such circuits: -RC Circuit - in systems with power supply of 24-48V, it is effective to connect the RC circuit in parallel to the load. When the power supply voltage is 100-200V, then in parallel to the contacts (in this case when AC is switched, the load impedance must be lower than the R and C impedance) -Varistor - the use is very similar to RC circuit, even with those conditions when in parallel to load or contacts. Varistor ensures that no high-voltage is imposed on the contacts. -Diode - energy stored in the coil is changed into current by the diode connected in parallel to the load. Then the current flowing to the coil is consumed and Joule heat is generated by the resistance of the inductive load. The diode must withstand a peak inverse voltage 10 times higher than the circuit voltage and a forward current as high as or higher than the load current. -Diode and Zener diode - this method will be effective if the reset time delay caused by the diode method is too long. Zener voltage for a Zener diode must be about 1.2 times higher than the power source. Ensure that the operating body will work smoothly. The shape of it should be round or oblique - to prevent shocks to the actuator. And of course, operate the actuator of a hinge roller lever or simulated hinge lever type from the right (correct) direction. Ensure that the stroke to the actuator is set not to exceed the total travel position. If not, the operating body may damage the actuator or the switch itself, and the stress applied to the moving spring inside the switch will increase and then, the durability of the switch may be deteriorated. And some more details - not to tighten the screws too much - not to deform the body of a switch. Or when soldering, adjust the amount of solder so that the flux does not enter the switch, it can cause contact failure. Should you choose a rocker switch for your operator interface? From this calculation, you can work out the expected number of operations over a year so you can find a switch with a lifecycle that can withstand repeated operation over the next 5 to 10 years without failure. So what exactly is a rocker switch? As the name suggests, rocker switches rock back and forth between the off and on position. When one side is pressed down, the other side will rise up. Most of them provide a ‘positive click’ feedback to let the user know the switch has changed position successfully. Typical applications for these switches include commercial and agricultural vehicles, surge protectors, computer power supplies, industrial assembly lines and many other types of industrial machinery panels. Some rocker switches with independent circuitry can be backlit to show their presence and function in low light levels. Others can be illuminated to show whether the switch is on or off. On any operator interface, if you decide to include rocker switches in your design, you’ll need to ensure you have enough space for the switch and information about what the switch is for. What is a push button switch? A push button switch is a type of switch which consists of a simple electric mechanism or air switch mechanism to turn something on or off. Depending on model they could operate with momentary or latching action function. The button itself is usually constructed of a strong durable material such as metal or plastic. Push Button Switches come in a range of shapes and sizes. We have a selection of push button switches here at Herga. Push button switches are used throughout industrial and medical applications and are also recognisable in everyday life. For uses within the Industrial sector, push buttons are often part of a bigger system and are connected through a mechanical linkage. This means that when a button is pressed it can cause another button to release. Examples of Push Button Switches Push button switches are present in so many areas across different industries and for different uses here are some examples; Calculator buttons – a hand held calculator has lots of small push button switches Reset switches – these are usually small and require a tool to press to avoid accidental operation Stopping machinery – often around industrial machinery there will be an emergency stop button, sometimes these are located on the wall Arcade gaming – these are usually brightly coloured to encourage people to play Slide Switch A slide switch is a mechanical switch that slides from the open (off) position to the closed (on) position and allows control of a circuit’s current flow without having to manually splice or cut wire.