I'm looking to design a basic system that I believe requires a solenoid interlock.

The basis of the system is a swinging gate. The gate has two positions, as you might expect - open and closed. There is a process that will be run which will only run when the gate is closed and locked. A microprocessor ties together the whole control system.

So, when the process is initiated (via a button), I want the system to check whether the gate is closed. If the gate is closed, I want it to be automatically locked. Otherwise I do not want the process to run. Once the process is finished, I want the gate to be unlocked.

A part solution to this problem is the use of a limit switch or hall effect sensor, however, this doesn't help with the locking part. As far as I'm aware there are products on the market which provide both functions in one.

My first thought of a device to use is some sort of locking solenoid switch. As far as I'm aware, these can be used to detect proximity (i.e. if the gate is closed) and then used as a lock. I'm not entirely what to search for. Some products I have found seem to only be compatible with some sort of proprietary safety controllers.

In terms of compatibility, I guess what I'm looking for is a device that acts like a switch. In my head, I'm imagining that when the gate is in the closed position a contact that is NO becomes closed. Furthermore, my thoughts for the lock is that it is a solenoid controlled by a contactor or similar.

What suggestions do you have for setting up a system like this? Is there is particular type of component I should be looking for?


closed as unclear what you're asking by Chris Stratton, RoyC, Dmitry Grigoryev, mkeith, Voltage Spike Nov 5 '18 at 23:16

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    \$\begingroup\$ Unfortunately, your problem statement is far too vague to make this an answerable question. Computational devices are absurdly literal, so you must specify exactly what you want to happen, under what conditions. It looks like there are a few words missing to even have a grammatically complete statement, but even putting those back in with an edit is probably still going to be short of an answerable question. \$\endgroup\$ – Chris Stratton Oct 29 '18 at 0:42
  • \$\begingroup\$ I've tidied up the question, adding further information and additional thoughts. \$\endgroup\$ – CircularRecursion Oct 29 '18 at 1:00
  • 1
    \$\begingroup\$ Still not really an answerable question. Actuators and sensors are conceptually distinct; sometimes sensors are built into actuators, but you might as well think of them as distinct functional items. \$\endgroup\$ – Chris Stratton Oct 29 '18 at 1:02
  • \$\begingroup\$ Your safety interlock has to check if locking the gate was successful. How do you do that? You need another switch for that. That's what those lock&switch combinations are for, I guess. \$\endgroup\$ – Janka Oct 29 '18 at 2:48
  • \$\begingroup\$ There are systems where the operator has to hold two switches ti prove their hands are not in the machine... accidents still occur because they put a brick on one switch - the boundless stupidity... \$\endgroup\$ – Solar Mike Oct 29 '18 at 5:59

Something like this: https://www.schneider-electric.us/en/product/download-pdf/XCSTE5311 Please note that machine safety has to use a safety relay, safety plc or some approved safety MCU.

Usually a standard PLC or MCU is used with additonally a safety relay. The safety relay disconnects power to the mahine and it has safety inputs, outputs.

What you are asking is a safety interlock switch/lock. You wire the safety contact as any other emergency switch, once opened the machine has to stop. When you close the doors, it'll lock them unless you supply the solenoid to unlock the door. Usually we put a push button to activate the solenoid that stays enegized for few minutes or less, this due to solenoid overheating and burning if they are constantly turned on.


Not the answer you're looking for? Browse other questions tagged or ask your own question.