I have this one working as a switch but can also work as a sensor according to the specs. I use it for my air exchanger. Never had a problem with it.
https://www.amazon.ca/dp/B08X218VMR/ref=cm_sw_r_apan_i_F0BBY5QX5AQ6C5TPRQFY?_encoding=UTF8&psc=1
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It does have a set of contacts used to control the internal relay via an external switch, but it does NOT report the state of the external switch. It is easily possible for the relay and the switch to get "out of sync." Is not the right device for this application.
I'd go with the Zooz ZEN16 or 17 and find 1 or two more things to do with the extra capabilities.
Just reading the Sonoff zbmini on/off relay from switching the input with a "dry" set of contacts should do the job for about $10. For that cost, I would buy additional spares and still save $$$.
You are free to try, but I don't think you will be happy with the results. The state of the relay does not match the state of the connected switch. The switch can be ON (closed contacts) and the relay can be off. This happens because the relay changes state any time the switch is toggled. In theory, you could get the relay OFF and the switch OPEN and hope they stay in sync, but they will very likely get out of sync, especially with a photo beam that can change from open to closed and back to open faster than the ZBMINI can respond.
But there is some good news. The ZBMINI is also a very useful device and I'm sure you will be able to find somewhere to put that to good use as well, I just don't think you'll be able to make it work for your photo beam application.
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I am using the Seco-Larm "Enforcer" with Retro-Reflective Photobeam Sensor (E-931-S45RRQ).
There is an adjustable output 5 ms. to 100 ms. response delay which worked perfect with my Shelly 1L "WiFi" switch - bad word on this forum. Moving to HE's Zigbee Sonoff ZBmini should not be a problem due to the Enforcer adjustment response delay. Thanks for your engineering concerns.
Will try this switch to see if it is reliable enough for my home automation/security system.
Why? Thereās a built-in integration for many Shelly products.
You can set up the Aoetec Sensor 7 to work in "Dry contact" mode.
See: Smallest Z-Wave door / window sensor with dry contact relay ā¢ Aeotec
Also see "Advanced functions." here:
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I am ridding all my home automation sensors and devices away from MY unreliable, overloaded WiFi and using Hubitat's Zigbee (3.0) and Z-Wave plus.
That might be your decision. But thereās nothing verboten about WiFi devices in this community. Which is what you implied by stating, ābad word on this forumā.
For $45 - I can buy 4 Sonoff ZBminis! Since my applications has 110 VAC power for the Seco-Larm then I would need to buy an additional power supply for the battery operated, contact sensor to
add more reliability to my system. Since this Seco-Larm is picking up only sidewalk visitors then it is a non-critical security warning sensor/device.
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Might also consider adding one of these to your order.... just in case 
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Cheaper is better if it works. When I find something cheap that works reliability then I buy in large quantities to save money.
Cheap and easy to solder a set of wires to each side of the switch and use as desired.
There's a handful of threads showing details of how to do this to a couple of different vendor's contacts.
Adding to this older thread on a low cost solution ($3-$6) for a Zigbee Dry Contact Input. I'm using a Water Sensor with a Remote Sensor. I cut the end of the sensor off and soldered the lead ends (note the wires are thin, like 24awg). I changed the Device Type to a Zigbee Contact Sensor and when the leads are touching the device shows closed, when not touching the device shows open.
I have one in use and it works great.
Virtually any water leak sensor that has two metal contact points is looking for a change in resistance to trigger the sensor. I clip the sensor off and take the two wires and use them as contact closure sensors for relays and such. As an example my home alarm system 12vdc output to the siren is tied to a 12vdc relay. If energized it will short the two wires giving me a "wet" trigger, HE then sends me a text to let me know that my alarm siren is active. Really inexpensive and been using them for this type of application for years successfully. Hope that helps j
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Second vote for this device. Long battery life, simple screw contact inside the case, and is easy to add/remove to Z-wave. On Amazon here.
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I use the ThirdReality zigbee water leak sensor as a dry contact sensor. Connect your switch contacts to the existing external screws and you are good to go. AA battery provides more than a year of service.
Exactly! I have boxes of stuff saving me money right now!
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Don't we all!
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