Hello, I need a recommendation about the safety sensors or limit switches for safety in the doors of my cell, I have a KR 3 R540 robotic arm with a KR C4 Compact controller, so I have two limit switches together that are activated synchronously , and I connected one to pins 3-4 and the other to pins 12-13 of my X11. As I understand it, that set of limit switches would only go to one door, but in my case, I have two doors in my cell as seen in the image. In which pins would I have to connect the other sensor for the other door?
Cell door security
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Andres -
November 10, 2021 at 4:12 PM -
Thread is Unresolved
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Is there a reason why you can't connect the switches in series?
Another this is: Are those limit-switches safety rated? If not, they should NOT be used for safety.
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First, what model controller is this?
Second, those pin pairs don't add up -- 3&4 are only half of the Safety Gate pair, the other half should be 21&22. Pins 12 is for an external deadman switch, only used for having multiple people safely in the cell at the same time, and has the same issue -- it's only half of the external enabler, the other would be Pin 29.
(all these numbers assume a standard KRC)
Normal practice is to daisy-chain multiple safety devices, electrically in series. Since all safety devices, including the X11 itself, are required to be dual-channel (and safety-rated), just wiring a typical DPST switch into both pairs may not work, and will definitely not pass legal muster. For example, the safety gate signals: Pins 4 and 21 would be to connect/disconnect to their respective TEST outputs within a few ms of each other, or the robot will throw a single-channel fault. As well, on X11, when you see an A signal and a B signal, they must only be connected to a TEST A or TEST B output -- any crosswiring will also throw a fault. These are not simple DC signals (unless we're talking about an ancient KRC1 or early KRC2), they have digital pulse-train "fingerprints" so that the safety board can tell them apart.
Any unused signals will need to be wired directly. For example, if you're not going to use the external deadman enablers, you have to wired them all directly to TEST outputs correctly. You will have to wired a dual-channel E-Stop button across the E-Stop inputs (bridging them directly and omitting an E-Stop button will be of questionable legality, and absolutely illegal for a KRC4)
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Perfect, thanks for the help, another thing, could you recommend sensors to place on the doors? You can give me brands or models to proceed with the purchase because I am using limit switches.
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i would consider something contactless like CN-S221 or pSen
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That's a subject with a very broad range of answers. The key is that the "sensors" must be safety-rated.
https://www.keyence.com/products/safet…ck-switches/gs/
https://www.rockwellautomation.com/en-us/products…k-switches.html
Also, be careful about devices that require some sort of extra software or tools to configure -- you probably want the devices that have simple four-wire connections. "Dry contact" is one of the key phrases to look for.
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Thanks for the recommendation