In many applications for moving mechanical parts and assemblies, it is important to know when a piece of machinery gets near another bit of machinery so some kind of action can be taken. So called “proximity sensors” do this job quite nicely and come in a large variety of sizes and employ many different types of tech to do the sensing.
Some proximity switches are contactless, using magnetic field detection, infrared beams, acoustic signals or capacitive detection that can be detected by a computer with an appropriate interface, located remotely. A great example is the prox sensor used in many vehicles now to alert you when you are about to hit the curb, or another car while backing up. Your mobile phone uses a light based prox sensor to prevent the classic “I didn’t take that stupid picture, my ear did,” syndrome.
It turns out that in many applications where prox sensors are used in outdoor vehicles or machinery, they have been less than reliable. No matter what kind of traditional proximity sensor that is used, the proximity signals they produce require interpretation by an external device or computer. Normal wear and tear of mechanical parts in a vibrating environment affects tolerances and can cause the sensors to misbehave. Most of these sensors are not robust as their very operational nature limits the amount of protection you can use if you want them to work reliably and keep them small. And of course the need for external processing of the signal at a computer or other control device, creates additional points of failure in the overall system.
Sometimes you Want a Proximity Switch, Not a sensor
It turns out that for applications from Roller coasters, to conveyer systems, to all kinds of work trucks, a hardened stand-alone waterproof limit switch, used as a proximity detector, is a far superior and less costly solution for outdoor applications. Even though these switches rely on mechanical contact to actuate, they have such a high electromechanical endurance, and such superior immunity to water, vibration and temperature, that they cost less to deploy and service over the application lifetime.
It’s not just us (CPI) saying this. Recently, another client of ours in the business of building aftermarket, customized work trucks, came to us after repeated failures of one of their proximity switches. This client essentially buys truck chassis’ and completely customizes them for field technicians and tradesmen in various industries. Their application is actually quite common across many work trucks and construction vehicles , as they need to detect the position of outriggers.
Some of these work trucks have small cranes mounted to the chassis which require outriggers for stabilization. In almost all outrigger systems, knowing when the outrigger is fully extended, and then knowing when it is fully retracted and locked, are key for safe operation of the vehicle.
While this application was using a proximity switch, this was not ideal. These sensors are not robust in a harsh environment long term, and can be highly susceptible to machine variances over time which cause them not to trigger correctly or at all. What this application really needed was “yes/no” proximity detection, not range detection. And it needed to be reliable in a harsh outdoor environment. Flimsy proximity sensors using magnetic detection were requiring too much field replacement and were an unreliable and an overly complex solution to a simple problem.
CPI’s New Line of Proximity Sensors/Switches
CPI switches have been reborn into many area’s formerly using proximity sensors for the same reasons engineers always select CPI: the highest performing and most reliable waterproof limit switches in the world.
Essentially any of our waterproof switches can be used as a momentary or maintained closure proximity switch by selection the right kind of mechanical actuator. A great example is our E1129 simulated roller switch, a robust limit switch with a simulated lever actuator. Completely made of high-grade stainless steel it is truly waterproof and completely customizable with almost countless mounting and actuator combinations available. Commonly used in applications where proximity detection is being done for end of travel detection on mechanical arms or supports, or door and hood closure applications, our E1129 can be used with any of our B series switches providing all manner of electrical flexibility and waterproof, high endurance operation.
E1 series, proximity limit switches can be a great solution to many applications where reliable operation is a key concern. This is owing to their relatively low cost, the way they may allow simplification of the overall system (no computer interface, simple open/closed) and the decreased cost of field replacement that occurs when a hardened switch rated to over 1 million cycles is employed. Other benefits include the possibility of local control of lights and alarms through a switch closure, while a prox switch has to have its sensor output transduced, interpreted by a computer which must then send electrical control signals to wherever they are needed. That’s an awful lot of complexity when all you want to know is whether someone closed the door!
Get in the Proximity of CPI Switches for your next Position Sensing Application.
It’s no joke that CPI switches are seeing more and more applications as proximity sensors. We think that’s because sometimes it makes sense to go back to something that works, in order to move forward.
Call our team today to find out about CPI waterproof switches for proximity sensing in your application.