Make a "clean contact" by changing a Sonoff Dual (R2)

5 minutes of reading
PURPOSES OF PROJET:
  • Make a clean contact (or rather, two) through a home automation actuator “Sonoff Dual R2"
  • Difficulty level: medium
  • Cost: <20 € (cost of the unit to be modified)
CONCEPTS FACED:
  • Modification to electrical scheme
SOFTWARE COMPONENTS USED:
PHYSICAL DEVICES USED:
PROJET MOST INDICATED FOR:

All environments

Notes and disclaimer
  • qualsiasi eventuale modifica agli impianti domestici dev'essere progettata ed realizzata SOLO da personale qualificato;
  • any changes implemented in probefore is a propersonal responsibility as well as a profirst risk and danger (the contents of the present page are purely educational);
  • any changes implemented in proprior to a device it voids the guarantee, quality approvals and certifications.
Driving review: 1.1

ATTENTION: it is possible to have an individual clean contact also modifying the most basic Sonoff Basic.
Alternatively, the Sonoff 4ch PRO presents four factory clean contacts, without needing any modification.

Abstract

A simple wall switch, to understand, is a device that, in a mechanical way, puts two poles in "contact".

The amount of current flowing through the circuit at the end is indifferent to him (except in the case of too much, but only for physical reasons that would lead him to break): it simply limits itself to open / close that segment of the circuit.

TheITEAD Sonoff dual is a dual channel home automation actuator that, by default, is designed to have 230v in and out 0v or 230v outgoing (on both exits), based on the state of excitation of its relays, or based on the fact whether they are "turned off" or "turned on" (individually or both).

ITEAD Sonoff Dual - Connections
ordinary connection scheme of the Sonoff Dual.

The change that prolet us place ourselves in the present procast causes that in outgoing contacts (Linea1 / Linea2) be absent - when the relative relays are activated - the ordinary, expected output voltage 230v. We will use these two contactsnameconnected to as many two (or one in common) as individually controllable “inputs”, while the two “neutral” output contacts present at the factory will no longer be used.

Let's imagine, for example, that we have a boiler for independent domestic heating activated through a traditional thermostat that for activation uses, for theappanointed, a clean contact. Replace the traditional thermostat which will allow it to be Sonoff Dual modified a clean contact allow to domotize domestic heating, because activating one of the two channels of the actuator we will close the two activation contacts of the control unit and vice versa.

Not only: another area of ​​use, important in personal home automation, that's it of remote control home automation rolling code.

Nb We recommend to reproprogram the firmware BEFORE the hardware change promailed by the guide. In case you need to do it later, to send the device in flash mode in addition to the classic Button 0 / GND jumper, a second will be placed between Button 1 / GND.

To whom would you like appromerge the concept of "clean contact" and its use in personal home automation, we recommend reading di this article.

Anatomy of the Sonoff Dual R2

The board it's like that:

Sonoff Dual - Board - Top
the board seen from above ...
Sonoff Dual - Board - Bottom
... and from below.

Prosubsidence

Before starting, we remember that:

Notes and disclaimer
  • qualsiasi eventuale modifica agli impianti domestici dev'essere progettata ed realizzata SOLO da personale qualificato;
  • any changes implemented in probefore is a propersonal responsibility as well as a profirst risk and danger (the contents of the present page are purely educational);
  • any changes implemented in proprior to a device it voids the guarantee, quality approvals and certifications.

Guys caution. Safety first.

La procedura is not very difficult, but it provides a certain manual skill.
First of all it is necessary to separate the power supply (i 220v) that serves the logical part of the Sonoff from the one that goes to the input of the two relays and eliminate the latter. To do this it is necessary cut the following connection:

Sonoff Dual - Board - Clean contact - track to be cut

The track to be eliminated connects the phase procoming from the large tinned track visible in the photo to that one that goes to serve the logical part. Specifically that track goes to connect with a printed micro fuse, not the traditional fuses, fuse that even after the modification continues to do its job that is procover the part of the logic circuit.

A recommendation: this operation must be performed carefully because the two circuits must be isolated, therefore a large cut must be made e probottom. THE

Once this is done, it is necessary make sure there is no longer a connection between the two points using theapposita function of the tester (so a tip on the large tinned track in the shape of "J" and one on the pin of the micro fuse, the one circled in red in the image above).

Bridge removal

At this point it is necessary to remove the copper bridge:

Sonoff Dual - Board - Top - Copper bridge and connections
original connection scheme of the Sonoff Dual (R2)

To carry out the removal is necessary unsolder the welding points placed at the bottom of the board:

Sonoff Dual - Board - Clean contact - unsolder bridge

At the end of the procedura then we will have removed the input phase to the two relays, actually making the two clean contacts.
However, they are not yet usable.

Since in the first step we removed the power to the logical part, it is necessary to restore it: without the Sonoff it wouldn't even come on. To do this we will go to connect two specific points on the board via a connection cable.

Sonoff Dual - Board - Clean contact - points to be joined

At the end of the procedura, the board appwill be more or less as follows:

Sonoff Dual - Board - Clean contact - completed

At this point we have transformed the two output contacts (formerly 1 Output Line and 2) into clean contacts. The entrance is missing: at this point we can equip ourselves with one or two entrances based on the need.

If the need is - for example - to pilot an element that includes two clean contacts and a single common entry (eg a motor of a tapparella activated with two clean contacts and with common input).

To acquire a common entrance, it is necessary to weld one thread to the following contact:

Sonoff Dual - Board - Clean Contact - 1 Input
board seen from below
Sonoff Dual - Board - Clean Contact - 1 Input - Top View
board seen from above

If you need them instead two separate entrances (eg to check two different buttons of a remote control), then they will be soldered two different contacts to be combined with the two clean and completed contacts cutting a track:

Sonoff Dual - Board - Clean Contact - 2 Input

Nb It is advisable to close with hot glue (or other insulating materials) the two known lines as "Neutral Exit”Native (see scheme above) with hot glue, so as to avoid any incorrect connections.

Verifica

Now to verify that the modification has been carried out correctly will be sufficient to measure using a multimeter that the potential difference between the input / inputs and the two output contacts of Sonoff (with relays obviously activated!) is even to 0 volt.

There must be no output voltage, in a clean contact. If you measure 230v (or any other value other than 0), change it it will not have been carried out properly.

utilization

Followed the proindicated you will finally have a Sonoff Dual changed to "clean contact".
As explained the uses are the most disparate.

A shining example is related to the use of this modified component as an actuator for domotizing an independent heating system. Very comfortable, in havenamento this change, comes the PULSETIME firmware command Sonoff-Tasmota, which allows us to transform the Sonoff Dual modified to a smart button. Actually the adoption of the firmware Sonoff-Tasmota is not a must (as much as advocated): it is sufficient, in fact, to use the "inching" mode of theapp eWeLink usually used when the actuator firmware is the original one.

Not only: another area of ​​use, important in personal home automation, that's it of remote control home automation rolling code.


The inDomus community thanks very much Gioz for his crucial support in drawing up this guide.
We also talk about this change on the forum.

What is (and what is it used for) a "clean contact" actuator in home automation


ITEAD Sonoff BasicATTENZIONE: remember that there is on our FORUM community an ad hoc section dedicated to Sonoff (and more generally to devices ESP8266), for any doubt, question, information on the specific merit of these components.

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