I want to share the capabilities of the T2 relay, for some users (as they say in the people “dummies”, please no offense :)) that it is just a relay that has dry contacts, but I want to break this myth about “just a relay”.
Let’s start our story with the history of the creation of the Aqara relay.
Initially, there was an extremely well-known Aqara 2-channel relay, which could only work with wet contacts at 220 volts. Craftsmen managed to convert it into a dry relay (by gnawing two tracks on the board) and some (including me) even perfectly started it to work from 5 volts with dry contacts. I still have this relay working for battery-powered emergency lighting (the relay is powered by 5 volts, the load is 12 volts).
Attention, I do not encourage making such changes to devices, this voids the warranty on Aqara and also electrical safety (a person with experience working with electricity)!
Now let’s continue the story about the newly created long-awaited relay T2.
This relay has a lot of useful and unusual things in contrast to the old relay.
The T2 relay now has a physical jumper that switches the relay from wet to dry contact.
The control contacts are brought out to a separate side, which is very convenient.
Let’s consider what settings Aqara gives us for the relay.
1- “Power-off memory” here the choice is quite extensive and clear, does not need any explanation.
2- “Switch type” selection of the operation of an external switch connected to the switch. There is a peculiarity here when choosing a pulse mode, I will tell you later and you will understand.
3- “Decoupled Switch Mode” is a mode that changes the physical button connected to T2 to a wireless switch, I emphasize once again, the switch (physical, on the wall or other) becomes an analogue of the Aqara wireless button, with only one action “press”. It does not control the relay contacts when pressed.
At this point I will return to the 2- setting.
Some users who have switched to the pulse mode of the “Press Button” relay (setting -2) complain that they cannot control other relays when using automation. To control the relay contacts, you need to have the wireless button enabled and then make an automation for the selected physical button (analogous to the automation you do for the wireless button and wall switch).
Also in this automation you need to include turning on (off) for the same relay (I call it “automation to itself”). An example of such automation is in the picture.
Also note that even the automation conditions of the T2 relay when using the “Press” mode have a small selection
4- parameter “Switch interlock”, this parameter theoretically (I emphasize, theoretically) makes a relay switch in which there can be a COM contact NO and NC contacts. You understand, the contacts themselves block each other.
Unfortunately, there is an unpleasant feature in this mode, I kindly ask you to pay attention to this! The button located on the relay body itself DOES NOT WORK in the interlock mode, it works in the On/Off mode for up to two contacts simultaneously. Therefore, I recommend that for use in reverse mode for motors, first install (pressing without load is possible) and then connect the equipment. Practice has shown that it is also possible to make emergency automation in which IF channel 1 and channel 2 are on THEN turn off channel 1 and channel 2. I tested these conditions, the shutdown is almost instantaneous.
5- parameter “Device mode”, this is one of the parameters that users have been waiting for a long time. It has the ability to select three modes, let’s talk about them.
A- wet contact mode, an analogue of the mode that was on the old Aqara type relay, there is no need to explain anything special here
B- Pulse relay operation mode.
Attention - for clean dry contacts, remove the jumper on the relay to work in this mode!
This mode has the following feature, you can select the time interval (setting range 300 msec (0.3s)÷-2000 msec (2ss)) when the relay will work. That is, On is set to Off delay.
As a rule, this range is used for pulse triggers for starting motors for closing roller shutters, blinds, or other commands that require an initial start to start other automation built on other control systems. In my other topics, I will describe the principle of operation of such control and give a link here.
C- dry contact mode.
Attention - for clean dry contacts, remove the jumper on the relay to work in this mode!
This is also the long-awaited setting of the T2 relay. Here the fantasy of use has no limits. Controlling a heating boiler (dry contacts for supplying a direct signal to the boiler control board). Controlling poorly accurate devices when controlling a 220 volt relay winding. Controlling two different voltages, for example, I control emergency lighting, the relay is powered by 24 volts and the contacts supply power to 12 volt lamps.
Note for developers of future versions of the Aqara relay (if they read my description) - make the relay control range from 12 volts, ideally from 5 volts. Old relays work quite well at 5 volts (read the beginning of the story), this will allow users to use even ordinary power banks to control the relay. You can imagine how the range of use of such a relay in everyday life changes!
A separate explanation about the relay when operating at 24 volts.
If you use a 24 volt relay, be prepared that external switches (com, s1, s2) will not work. I warn you right away, do not experiment with applying other voltages to these contacts (com or 24 volts) to make the switches work. Learn from my mistake, I broke one relay during the experiment, broke the control system from the switch (com, s1, s2).
Features of control at 24 volts, control from the program or using automation (scenes)
This will end my story.
As I write topics related to the use of the T2 relay, I will provide links to them here.
Thank you for taking the time to read the description.
no worries, I enjoy good humor 
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