You enter the laundry room and the washing machine is spraying water in all directions, it’s raining indoors! My new washing machine has one of these new fancy touch panels so it is sealed from the rain, but will it switch off with water running all over the controls? I make a dash to the control panel and touch the “Power Button”; the rain stops. Modern technology works!
Water has been the enemy of technology for decades because of its damaging effects. Touch sensors have been known to work improperly (or not at all) when they come in contact with water. ON Semiconductor’s solution to Touch and Proximity sensing simplifies and speeds up the design by utilizing a differential sensing technique that eliminates many of the problems with operating under wet conditions (spilt liquids or being operated in the rain), long sensing traces, operating in noisy environments, and special assembly techniques.
The differential sensing automatically neutralizes electronic noise as both inputs receive the same signal and thus it cancels out. The differential detection is 5 times better compared to single input detection.
Sensor Lead length is equalized by the differential input. The capacitance between the sensing leads being neutralized.
The sensing pattern on the printed circuit board only needs a few millimeter air gap below a thin protective panel. No need for special light guides or conductive adhesives.
All of this is just part of the LC717A00 and LC717A10 Capacitive Touch IC. For more information please review Capacitive Touch Sensor Application Note and Design Note.
The Touch control panel in this example was designed using the ON Semiconductor LC717A00 Capacitive Touch IC and with a simple layout of the sensors it can be operated in the rain! So what was wrong with the Washing Machine to cause it to spray water over everything? The pipe that fills the drum had come loose.
What mishaps have happened to you where technology could have helped?