Velux opening skylights and blinds integration (older hardwired 22-24v system) -- How to integrate with ST? (DPDT)

I have multiple hard wired, low voltage DC controlled, Velux opening skylights with blinds. I installed the skylights and blinds 15 years ago during a remodel. I am not an electrician by trade but have fairly good knowledge of both AC and DC wiring systems.

The skylights and blinds open and close with 22v DC hard wired motors. I believe the newer Velux stuff is all connected via RF and driven by remote control, but this system is not. This should make it a lot easier to connect to a home automation system. Since the skylights and blinds open and close with simple DC motors, to open them requires closing the switch in one polarity and closing them just switching in the opposite polarity. Essentially what is required is a zWave controller with a DPDT configuration that can flip a relay in one direction to open the skylights (and blinds) and reverse the polarity to close them. there are limit switches built into the windows and blinds so it is not a momentary type switch that is required, but rather just a normal DPDT on/off switch .

I hope this makes sense. Does anyone make a zWave or Zigbee DPDT switch I can connect to my Smartthings hub to get my skylights and blinds automated? Or if anyone has other advice on how to make this work it would be appreciated!

I’m pretty sure a Mimo2 can do this, but I’m not sure if anybody has written a SmartThings device handler for it yet. But the same company’s Mimolite is quite popular, so it may have been done.

@Mike_Maxwell has done a lot with relays, he might have more to add.

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Hey JDRoberts,

Thanks for responding! I checked out the MIMO2 module link you gave out. I am a bit confused on how it works as it is a bit over my head. It seems to be able to trigger the DPDT relay via voltage variable inputs? I would not be using that functionality, correct? I would just need the relay to be thrown via a zWave command, correct? It seems to have more functionality than I require which is fine if it can do what I need it to do, which is to throw the DPDT relay on a zWave command for up/down or on/off or whatever Smartthings or I will call it.

I guess I can check with SmartThings to see if it is compatible, but it looks like the MIMOLite is compatible (switch mechanism only and not ‘input ability’ as that is still in development per the Samsung notes) MIMO2 is not even being sold yet. At least not on Amazon or directly on their site. Any idea when it comes out?

My bad, you’re right, the Mimo2 would be for bridging in the other direction.

Off the top of my head I can’t think of any DPDT zwave switches, but that doesn’t mean they don’t exist. Hopefully one of the community members who’s done more with relays will know.

To be more clear, I have found a couple of schematics to get the point across on what I am trying to accomplish.

To work a DPDT switch to reverse polarity for a DC motor:

To do this while also having it in a ‘center off’ configuration requires two coils, one to throw it one way and one to throw it the other way, with both sets of poles connected:

That would be the ultimate setup for this so neither side is energized all the time.

Anyone with input, let me know!

I used two MimoLites for this, albeit using Vera. My window controller reports open/close status so I use one of the MimoLite inputs to capture their state.

With ST, two LFM20 units would work in your application. These are isolated contact relays, so you would use one on each coil. The LFM20 can be set up in ST as a latching, or momentary relay by changing the device handler using the web IDE. You can tweak the momentary time if needed…or just turn the relay on and off. I use one of these in ST to control our ERV.

There is a garage door smart app that would work well, if you add an ST contact sensor to one of the skylights. The smart app figures out if the windows are open or closed based on sensor state.

My understanding is that the problem with using two single pole relays is if either a user error or a network error results in both switches being thrown at the same time, you can burn out the motor or have other unpredictable results.

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Good point. We ended up using a Vera Edge (onboard processing) at the office location as ST (using at home) is not reliable IMHO as a business solution. I’ve found that the PLEG addons to Vera make pretty much any automation possible, once you spend some time with it.

After setting up two locations with fairly extensive automations, one with Vera, the other with ST, the strengths and weaknesses of both systems are pretty apparent.

Can I assume the Windows incorporate limit switches to kill the motors? The SolarSmart Window operators I’m using have a wireless ECI remote with dry contacts for both open and close…so I don’t have any experience with wired systems…

I called the folks at Fortrezz who confirmed the Mimo is not available yet. My understanding was that it had two relays onboard, but not necessarily DPDT. The Mimolite relay (to the OP) is operated by zwave on/off commands like a switch. Fortrezz is quite familiar with ST, so call them with questions.

Great input guys! Been surfing all night trying to figure this out. Good points you offer. Yes, the windows and blinds both provide limit switches to kill the motors.

I think I have found the perfect solution. Two DPDT relays ($9.00/ea on Amazon) wired together give a good reverse polarity offering with a ‘center off’ option with no chance of blowing up the motor if both coils engage at the same time (see below diagram) Super cool solution!:

Pair that with a low cost dual relay on/off zWave module ($30) and you have what (I think) is a decent solution.

Makes it a sub $50 solution per skylight/window blind which, when you have 4 of each, is important as well. Let me know if I am way off on this but I think it can work. Wish me luck on the wiring of 8 of these combinations. Yikes! Hooper… we’re gonna need a bigger box! (for those of you old enough to remember the movie Jaws)

This relay is designed to power lights, so is not isolated…it feeds 110V to the two outputs based on input from the manual switch. Because it’s also powered by 110V, you can’t change this behavior. If I understand correctly though, you will use these with isolated manual relays, correct?

This is my setup which controls four Windows. The openers are solar charged and wireless, no wiring required. The LFM20 on the left is used to control our commercial HRV…part of our night cooling solution.

Cool setup you have there Denwood. Yes, it will be an isolated DPDT relay running the 24V DC wiring. Not sure what you mean by manual, though? The MIMO switches definitely have too much functionality for my project as they are meant to take action based upon an input sensor going off. All I need is a isolated DPDT relay for the 24V switching and a pair of zWave switches to run it.

I received some great feedback from Mike Maxwell . Instead of using two relay’s for each skylight like I posted earlier, I can use just one by using one zWave switch to power the relay and one zWave switch to power the coil of the relay . Energizing the one zWave switch providing power to the relay will engage the motor in one direction and engaging both zWave switches at the same time will reverse the polarity and engage the motor in the other direction. And this still provides full protection from accidentally energizing both sides of the motor at the same time.

The motors do have limit switches but it is still a good thing to be able to have the ‘center off’ function as well with no power going to the motor at all. Just provides greater safety from breaking things if one of the limit switches go bad. By turning both zWave switches off this accomplishes that as well.

This is my first Smart Home project. I have not even purchased a hub yet and have no idea of the look and feel of the interface, but I assume you have the ability within the software to energize the switches for a certain amount of time? About 10 seconds is all it takes to raise the window or blinds and the switch(es) can then be turned off. I am hoping this kind of timing feature can be accomplished in the software?

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The Mimolite doesn’t require a signal input to fire the relay, although you can set it up that way. In my case, I use one relay to send an open command which is sent via zwave on the controller. I use the signal input on one of the MimoLites to tell me if the windows are open or closed. The wireless ECI remote reports open/close state via a third set of dry contacts. This current window open/close state in turn is used in my automation logic

You may need to use the fledgling Core/Piston smart app to create your own rules to manage this on ST. ST has been getting more reliable but I’d still consider it a risk if an automation bug could damage physical equipment.

With Vera, I’m using the PLEG plugin which allows you to create your own logic to automate pretty much anything and uses 100% local processing on the Vera Edge so a web problem won’t disable your automations. The windows for example only open if temp inside is above 20C, temp outside is below 19C, forecast high for the day is above 12C, and the system is not in active cooling or heat mode. I also have night cooling automations that actively pre-cool the building between 12 and 5 am using the windows and a building ventilator.

Mike is a code wizard on ST, so should be able to point you in the right direction :slight_smile: The first step is to make sure your zwave relays are supported by ST.