Membrane switches and keypads are used in control systems for a variety of industries, from agricultural to medical to fitness. They are used as a user interface between a person and the operating system of equipment or machinery. There are two main types of membrane switches available, tactile and non-tactile, that differ in their method of feedback.
Deciding which keypad feedback to use for your application is related to what the keypad will be used for. Both tactile and non-tactile membrane switches are useful, but they differ in their construction and primary purpose.
Tactile Keypads Provide Tangible Feedback for User
Tactile keypads are momentary switches, meaning they are only active while being pressed. They provide a physical feedback to the user through a metal dome or formed plastic beneath the overlay. When a key is pressed, the dome collapses and makes contact with the conductive under layer, completing the circuit. This causes an action to happen.
When the user removes pressure from the key, the dome pops back up, eliminating the circuit connection and causing the action to stop. They are internally vented and sealed to prevent contamination.
Tactile switches are used for many household devices, like remote controls and microwaves. They also work great in noisy environments where a physical response is a more efficient message than a sound or visual cue.
Advantages of Tactile PCB Membrane Switches
Tactile membrane switches offer several benefits. These include:
- Immediate indication that a switch has been activated
- Metal domes are durable in extreme temperatures
- Improved accuracy
- Metal domes are available in a wide variety of sizes and actuation forces. Stainless steel domes may also be available with an optional nickel plating
Non-Tactile Keypads Utilize Light and Sound for Effective Feedback
Non-tactile keypads are similar to a tactile switch, but when pressed, there is no tangible feedback response. Instead, they require another way to alert the user that the switch has been activated. Typically, they rely on a sound or visual response from the unit.
Instead of a metal or plastic dome beneath the overlay, the non-tactile switch uses two layers of polyester with a conductive coating on each layer. When a user pushes a key, the polyester layers flex and make contact closing the circuit and initiating an action.
Non-tactile keypads are frequently used for sever environment applications. They can utilize a thicker graphic overlay for increased protection for the switches and displays. These constructions are known for their reliability in nearly all operating environments.
Advantages of Non-tactile PCB Membrane Switches
- Very ruggedized design
- Long life cycle
- Easily made into custom shapes and sizes
- Lower cost