electric curtains on ebay

The electric curtain tracks on ebay at the moment includes a photo with RJ45 port labelled C-Bus Compatible Network Port.
Do you think that this mean you do not need a Shutter relay?
sale item 272035167215

 

The network port is a bit of a misnomer. It is used for manual control where you can connect 2 switches to it. One switch for up, the second for down and both together for stop. To control it via CBus you would need to use 2 channels of a standard relay and use 2 cbus switches set for bell presses or write a bit of logic to use 1 toggle switch.

 

Personally I believe you are better off with a four wire motor and use the shutter/blind controller. You will get better control over the motor and have the ability to open part way.

 

In general I would have to agree with you. The main problem I have with the shutter relay is that it doesn't implement logic so interlocking with open windows and doors is difficult. Using the 2 relay approach with an inbuilt controller makes interlocking easy. The other big annoyance with the shutter relay (while I'm on about it ) is that you have no way of knowing the position of the blinds and displaying their state on a screen. The whole implementation is really very poorly thought out.

 

Isn't the GA value a representation of the position. Now granted, someone can move the blinds manually (say curtain track) and you lose your true position, but you would need feedback from the blind/curtain/shutter to know where it really was.

What am I missing?

 

If you use any of the toggle modes or stop command you send special GA values (e.g. 2% for stop) so the GA is only meaningful for fully open and fully close. If you use level translation mode the GA gives you the rough position, but level translation mode can't be used from switches so it's not much practical use.