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I am trying to find a safety sensor for a machine. The sensor should be safety rated as it will be used to detect if a cover is removed and will shut down robotics and uvc bulbs which is harmful to the service engineer (users will not have access to remove covers).

My issue is that I need one that is compact and small and also isn't ridiculously expensive as 4 of these are used per machine.

I had looked at limit switches though my main concern with them is that the contacts could fuse together over time as the switch will be pressed in the down position for about a year before a service engineer will be removing the covers.

Another type I had looked at was magnetic switches, however I was haviing issues finding one small enough. I also looked at inductive sensors.

Does anyone have any recommendations? Or any experience in safety sensor systems who can advise on the best types of sensors for my application?

cath001
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  • Welcome to EE.SE but please note that direct shopping questions will result in fairly prompt closure of your question as per [site rules](https://electronics.stackexchange.com/help/on-topic). You need to quickly remove that from your question and ask technical questions only. "*I had looked at limit switches though my main concern with them is that the contacts could fuse together over time as the switch will be pressed in the down position ...*" That's why safety switches don't rely on springs but the contacts are forced disconnect when the guard is being opened. – Transistor Sep 26 '19 at 18:30
  • In addition, [safety relays](https://electronics.stackexchange.com/questions/240280/symbol-or-marking-on-safety-relay/240352#240352) and dual channel monitoring may be required based on a risk assessment. – Transistor Sep 26 '19 at 18:33
  • They have specs for this, you should chose which specs you need then find equipment with those specs – Voltage Spike Sep 26 '19 at 18:56
  • What safety certifications should I be looking for when choosing a sensor? – cath001 Sep 27 '19 at 09:30

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They come in all varieties, like induction switches, mechanical switches. They are all ridiculously expensive, moreover you need to connect them to a safety PLC or safety relay which are also ridiculously expensive, safety sensor without safety module (PLC, relay,..) has no safety functionality.

Instead of using cover safety switches, you can bolt the cover with special screws. If they are non-standard it means that you need a special tool and it is assumed that only trained personnel would open the cover, so he/she knows the risks. Further you apply a sticker: Do not open before disconnecting power wires.

enter image description here

Marko Buršič
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  • These type of fasteners have never stopped me from getting in to anything – Voltage Spike Sep 26 '19 at 18:56
  • You do need a tool to remove this. _any screening within the protective housing so that tools are required for their removal;_ (tool denotes a screwdriver, a coin or other object which may be used to operate a screw or similar fixing means) – D Duck Sep 26 '19 at 19:50
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    @VoltageSpike Me neither, but it can stop some bureaucracy. – Marko Buršič Sep 26 '19 at 20:08