Alert on simple contact closure. Any suggestions?

solid0711

n3wb
Jul 31, 2025
2
0
United States
I'm looking for a solution to alert and record based on contact closure to monitor when someone enters through a gate. Any suggestions?
 
This device will probably do what you want, there may also be other ways to do this!
How does that do recording? It seems just to be a set of USB controlled relays.
Unless I've misunderstood the spec.

Many cameras, and more NVRs, have the ability to trigger recordings from wired alarm inputs.
 
How does that do recording? It seems just to be a set of USB controlled relays.
Unless I've misunderstood the spec.

Many cameras, and more NVRs, have the ability to trigger recordings from wired alarm inputs.
It does not do any recording, it is nothing more than an input module that can trigger BI to record or alert etc. The first one has the ability to take inputs and do outputs from BI, the second one only does input, the inputs are isolated so that there is no direct signal into the computer!
 
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Going to need some more information about what you’re working with but these devices are quite versatile and relatively cheap.
Careful though, after TonyR turned me on to them they and other Shelly devices have multiplied faster than cameras around here

IMG_0637.jpeg

 
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How does that do recording? It seems just to be a set of USB controlled relays.
Unless I've misunderstood the spec.

Many cameras, and more NVRs, have the ability to trigger recordings from wired alarm inputs.
With the Shelly device one would be setup at the gate to sense the contact state while the other would be at the NVR to change states accordingly.

Of course this is assuming there is already a CCTV setup, I think Bruce_H and I may be getting ahead of ourselves
 
Bruce_H, thanks for the suggestion. That looks as plug-n-play are you can get. Is there any delay for the alert when using this on BI?
I was testing one and the signal to BI was virtually instantaneous from what I could see, I did not do any definitive testing of the actual delay, but I am sure it was not longer than about 1 second!
 
This is the one I might get someday because you can hang it on a POE port anywhere on the network. Another version with added relay outputs is a bit more $. I can't confirm that it works ok with BI, but everything I see sounds like it should.

eI/O PoE Modbus TCP w/ 4 Isolated Inputs
 
I've automated a virtual doorbell using a Shelly and Home assistant. There is a dahua integration with HA. With the camera onboard face detection I activate the Shelly relay to drive a cheap eBay doorbell. Works a treat.
 
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They’re great little devices that can be isolated from the internet on their own VLAN and integrated into Home Assistant easily. At the top of my list is the PM “power monitoring” versions which allow me to see when the pool filter needs to be cleaned as well as one on the HVAC system to monitor the air filter.
 
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