Sonoff snzb-04 delay sending activation signal - alternatives?

Hardware
#1

I recently got a couple of the Sonoff SNZB-04 contact sensors in for testing. The initial use for this device was to sense the opening of a closet door to turn on the interior light in the closet.
As it turns out, there is approximately a one second delay between the two parts of the sensor separating before it is shown as ‘open’. While this isn’t much of an issue when this switch is used as a window/door alarm, it is rather disconcerting when one opens a closet (or drawer or what have you) and expects the light to go on only to have a VERY noticeable delay. The funny thing is that there is no delay when the contacts are closed.
Question: Is there a window/door sensor that is in a similar price bracket as the Sonoff device but is acting instantly without delay) ?

Edit: I did confirm that the second unit behaves in a similar manner.

#2

One second is pretty good for a battery powered wireless sensor that spends most of it’s time asleep to conserve the battery.

If you want faster you’re probably going to have to go for an “always on” solution.

I use a concealed wired reed switch on my linen closet doors.

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This is wired to a raspberry pi running a GPIO to MQTT bridge (along with a whole bunch of other sensors).

I guess it depends how much effort you are prepared to put in and if it is actually possible to run this sort of cabling to somewhere with permanent power.

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#3

I was considering going that route but wanted to explore easier possibilities first. I just placed an order for some TUYA door sensors as some posts I have run across are suggesting they activate instantly.
There is little reason for the delay - the device should stay asleep until it is woken up by an interrupt which can be dealt with quickly. Waking up every second and checking for activity is likely to waste a lot more energy then being in deep sleep until woken up.

I can go fairly simple with a WEMOS 8266 based board and a reed switch and this is quite possible in my test setup as I have power in the closet but I’d like to be able to do it with battery power in case I do not have power to the location of the sensor. Hard wiring things is really not an attractive option once the drywall is up and painted.

Thanks for your input!

#4

What are you using as an interface between the pi and the sensors? Or are those relay boards ?

#5

This (a bit out of date, but mostly still relevant):

#6

These https://www.zigbee2mqtt.io/devices/MCCGQ11LM.html from Xiaomi are pretty quick, but you may not want to invest in a zigbee infrastructure.

#7

nickrout, the link you posted is al about zigbee and mqtt. My sensor system runs zigbee but not over mqtt. Will the Aquara sensor work with a Sonoff zigbee bridge ? If the combination of Aquara and Sonoff zigbee bridge works then I could bring in a unit to try it out.

#8

The technicalities of what does and doesn’t work with the Sonoff SNZB-04 is beyond me.

Ultimately zigbee should work with zigbee, but the reality is unfortunately not real.

Someone here should be able to tell you though.

Getting started with HA Hardware
#9

Thanks for the details, an interesting project!

1 Like
#10

I decided to order an Aquara door/window sensor as well so I will be able to compare all three - Sonoff, Aquara and Tuya. Any devices that don’t trigger immediately will be used for applications not involving turning on lights.
If I remember, I will post the speed of actuation for all three devices in case anyone else is trying to find the right sensor.

#11

I have a Sonoff Zigbee Bridge & have tried three other devices. A water sensor. A light sensor and a vibration sensor. The water sensor works & eWelink thinks it is a door. The other two don’t. I suspect as your two are in a class already supported by Sonoff you’ll be okay. The other option is to flash it with Tasmota & control it locally with the homeassistant Zigbee integration. The Zigbee bridge doesn’t have a local mode so the signal has to ping up to their servers before home assistant records it anyway. A mistake I think. I don’t know why they didn’t offer a local mode, atleast for MQTT if the onboard memory isn’t enough for a scene.

#12

Hmmm … same setup-Sonoff Zigbee bridge and ewelink flood/water sensor and it is recognized by the zigbee bridge which talks to Home Assistant - worked without a hickup, just perfect! This is without talking through the ewelink app.
The zigbee bridge was re-flashed to talk to HA without going through ewelink servers.