Connecting Shelly Plus 2PM to a DC Awning Control System

klausbreyer · PHOTO-2024-02-19-20-32-36.jpg

Hi everyone,

I'm working on a project where I need to integrate a Shelly Plus 2PM with my awning control system, which is powered by DC with a control voltage of 24 V DC. The setup is as follows:

There's a red wire connected to 'L', which I assume is the positive (+).
There are also yellow and white wires for up and down directions, respectively.

I'm trying to figure out how to connect the Shelly Plus 2PM to this system. I understand the red wire is likely the positive one, but I'm not entirely sure how to proceed with the yellow and white wires. My concern is that connecting them in any way might immediately send a signal for the awning to go up or down.

I've been looking for guides or videos on how to connect Shelly devices to DC systems, but all I find are instructions for AC connections. I'm a bit stuck and would really appreciate any advice or guidance on how to properly set this up without causing any damage or unintended operation.

Sorry for the trouble, and thanks in advance for any help!

thgoebel

Welcome to the forum!

At first we would need the type and the producer of the awning system - or, better more, a link to a manual! The issue is, with three wires at a switch you may even not find out if the red wire is positive or not…

Using a Shelly plus 2PM with 24V DC has the following restrictions:

(a) The two relays of the Shelly are switching ground potential, not positive voltage.

(b) Power measurement is not available in DC operation. In consequence, a calibration is not possible!

klausbreyer

Thanks for the warm welcome!

This thing here is the control unit for the awning control system: https://smartbuildings.warema.com/de-de/steuerun…-kompakt-6-reg/

According to the manual, the red one is a plus. The other ones close a circuit to signal if the awning should go up or down.

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The cable in the wall has several wires that I believe are not in use, at least not by the switch. Can I send a negative signal through these from my control box? If so, where can I get that minus signal from? Does it need to come from the same power supply as the plus signal? Sorry, I am embarrassed about how little I know about DC. Or is there any possibility that I can get the minus signal for the Shelly from the other cables?

thgoebel

Thanks for the link! This allows the following conclusion:

(a) The current for controlling the MSE unit is very small:

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Max. 1mA is needed!

(b) Given (a), the appropriate Shelly device is a UNI (or UNI plus). Its two outputs are capable to switch 100mA max. (UNI plus 350mA max.) - more than needed.

(c) Unfortunately, the manual does not indicate a maximum current which may be drawn by external devices from the integrated 24V DC supply. This is crucial, cause it would be perfect to supply the Shelly UNI from the MSE unit instead of installing a separate power supply.

Leaving item (c) unanswered and assuming the power of the MSE supply would be sufficient, the following diagram is suitable:

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(If Shelly UNI plus shall be used, the common wire of the two buttons (blue drawing) has to be connected to pin 2, not to pin 1 of Shelly. Moreover, it’s not clear whether manual push buttons are necessary. In this case, diagram for Shelly UNI plus is identical with the above shown.)

Finally, the crucial issue is unanswered: Is the MSE unit capable to supply the Shelly UNI with 20 to 30mA @24V DC? This has to be determined in situ.

In the - not very likely - case the power supply of the MSE is NOT able to furnish the extra power, the Shelly has to be supplied with an external voltage: 12V DC, 24V DC or (with a Shelly UNI plus) even 5V DC are applicable. Another circuit diagram shall be provided for this solution…

klausbreyer

ah - the uni. Interesting choice. I had it, but it was totally not on the radar.

Are there any differences to the Plus 2 PM - from the usage point of view? Can I use it for awning controls move them to a certain percentage up / down?

Or can I just install the uni in my control box next to the MSE Kompakt 6 and use it in parallel with my switches?

Thanks for the good advice!