Question about terminals on the back of my DIY system

[KJDK]

Hello Good people. I come to You with a question I have about my recently installed DIY home alarm system.

 

I have made a system of a mixture of wired and wireless sensor in case of more clever intruders.

 

When I installed my system I noticed a set of terminals on the back of the alarm system that I can not figure out what is used for.

 

The connections are labelled 'Normally Closed' (NC)  + GND - just like my hardwired sensors I reckon.

 What is this used for? How Can I utilize it?

The User manual states that it is for external devices that require a N.C. signal and a motor is given as example. Since the entire system is powered by a small samsung 5V1A usb adapter, I figure it is very unlikely the intention, that I power a motor through this alarm system. If it was a N.O. connection I could use it to turn on a relay incase of an alarm - but since it is N.C. I just can't figure out how it's applicable? It is not for powering sensors either because there is another dedicated 9V connection for this purpose.

 

I'm trying to think of any scenarios where and why this connection is useful - In other words, I would like to make use of it my self but need help on figuring out what I can do with it.

 

I'm not from the UK so please excuse me on misspellings or grammar errors.

Edited September 16, 2017 by KJDK
fixed a few obvious errors

[al-yeti]

Well NC can still switch a relay , you just use the other terminals 

[james.wilson]

what system runs on 9v?

[KJDK]

@al-yeti : Thank You for your answer. I did not know that. I'm learning things as I go along and thus has never had to use a relay before.

 

@James Wilson : I think most 12V sensors have a rated operating voltage of 9-15v .. some even 6-15v ... I'm guessing that 12v is just a common label. Just like 220v is actually 240v and UK 240v is actually 250v or is it 280.. But I'm not from the UK nor an electrician so I may be wrong. I expect the alarm system has a step-upper build-in, in order for it to be able to provide 9v while running on a 5v standard samsung usb adapter. The system I have is called "GSM/IP Alarm System" - its a square white box with touch keys - it supports WIFI/GPRS/GSM, Has 39 zones and 4 hardwired zones. I've gone for wired glass break and reed sensors and a couple of wireless door sensors that'll probably get replaced by more wired reed sensors. I'm unsure weather I'm allowed to post a link for my DIY system - It's a Shenzhen generic sold under different labels I think.

 

If the N.C. connection in mention is for controlling a relay then would it not be possible to connect the following things? Here is a little mashup that I'm hoping a bright mind can tell me how to connect properly.

Edited September 17, 2017 by KJDK
fixed a few obvious errors

[al-yeti]

Why not?

 

Think about it the relay if always on will still have contacts that are open , which would close when the alarm is open 

[datadiffusion]

1 hour ago, KJDK said:

Just like 220v is actually 240v and UK 240v is actually 250v or is it 280..

 

The UK is officially 230VAC like the rest of the EU, but this is a nominal figure, which allows an upper tolerence limit within which 240V (which is what you'll mostly measure 'in real life') is quite acceptable.

[al-yeti]

1 hour ago, datadiffusion said:

 

The UK is officially 230VAC like the rest of the EU, but this is a nominal figure, which allows an upper tolerence limit within which 240V (which is what you'll mostly measure 'in real life') is quite acceptable.

What you think is mostly measured?  don't understand this stuff man

[datadiffusion]

_{I mean if you stick your true RMS fluke into the socket you'll read about 240v.}

[al-yeti]

22 minutes ago, datadiffusion said:

_{I mean if you stick your true RMS fluke into the socket you'll read about 240v.}

Nah man sounds like blag