jsburger wrote:Can someone in the know speak to membrane touch switches. I don't think internally they are any different than things that have "discrete" buttons like some remote controls. The internal contact is pretty much the same. It is a conductive "rubber" membrane. I am with Ed. I have a stove and fridge with membrane buttons that are 17+ years old with never a problem. The microwave is around 10 years and no problem. My Power Pro is 6 years old with no problems.
The thing about the membrane is that it is sealed on the outside. A good thing for something like a SS and pretty much everywhere else they are used.
Discrete mechanical buttons MAY last longer but they would not physically fit in the SS application.
I’ve designed quite a few industrial-control products in my career, and it’s been maybe 20 years since I designed any with membrane switches. Industrial stuff has gone primarily touchscreen since then.
The last time I specified membrane switches, switch life was rated at 5 million cycles for a no-frills keypad. But those had almost zero tactile feel, so we would typically specify the optional “click domes” that are placed beneath the membrane, one over each switch. The tradeoff was that the click domes reduced the rated life to only one million cycles per switch. But that’s still plenty of cycle-life for most applications.
One controller that I designed back in the 90’s had a membrane keypad that was used heavily in high-production machine shops. After 10 or 15 years of daily use, the most common membrane switch failure was the outer plastic membrane layer itself wearing out and developing holes over the click-domes.
Good-quality discrete industrial switches are typically rated for ten million mechanical cycles, IIRC. But the electrical life of the contacts can be far less, depending on the current, voltage, and the nature of the load.
Early on, touchscreen reliability was far worse than membrane switches. That that has improved greatly, and there are a variety of touchscreen technologies from which to choose. But I still had the touchscreen on a $1500 PLC fritz out on a prototype system just last year. And of course, lacking a tactile vibrator such as on a smartphone, tactile feedback is pretty much nonexistent on a touchscreen.
But touchscreens do have two huge advantages. First, the screen layout and graphics are configured entirely in software. So you can easily add features and improve the user interface with just a software update. Second, the hardware is basically generic — just pick the screen size and resolution that you need. This greatly reduces upfront development costs, which in low-volume products may actually be more important than the unit-manufacturing cost.