Alarm/interlock suggestions?

[dizzydee86]

Hi
I would like to alarm two gates at the rear of a property. They are used throughout the day for access but it is important that at least one gate remains closed if the other is open. I was thinking of using door contacts on both of the gates that could alert indoor sounders should both be opened at the same time? Rushed into this without much forethought and proceeded to purchase an alarm panel and sounders but now unsure what contacts I would need? Want to try the DIY route before calling in the experts but don't want to waste more money on the wrong equipment.
Any suggestions greatly appreciated.

 

[oasistechnical]

to be honest i would contact a local firm to give you a quote on what you need and what you want to do.

the kit you would need would have to be water tight (IP68)
and would require some real careful planning

just my idea, maybe one of the other on the site could offer any info ?

John

 

[scott1980]

If you want to keep it simple, you don't need an alarm panel.

Put a suitably weatherproof contact on each gate (a roller shutter contact would be ideal, but you would also need an IP rated box and gland to terminate the cabling from it into)

Connect them both in parallel, and bring the wiring back to a 12v boxed power supply. Send 12 volts down one wire, and connect the end of the other wire to the 12v input of a transistorised relay. Connect the negative of the relay to the negative of the supply.

What you have now is a circuit that will allow each gate to be opened individually, but if they are both opened at the same time, it will change over the relay contacts. You can then connect a sounder/buzzer/strobe to the contacts of the relay, with a keyswitch inline to disable if needs be.

Only problem there is the sounder would only trigger aslong as both gates are open. If this is a problem, use a latching relay and put in a push to break switch to drop the power to it to reset.

 

[dizzydee86]

Thanks oasistechnical, the correct advice really but still would prefer the DIY route 1st as far cheaper & more fun (if it works)!

scott1980 - I like the sound of your suggestion, I have plenty of Dantech 12V power supplies and some IP rated exterior boxes, the roller shutter contacts don't seem too expensive and I already have keyswitches and both alarm sounders and leftover fire alarm sirens which operate on both 12V & 24V I think. I only want the alarm to sound only if both gates are open so this would be a good solution. I presumbly could just use alarm cable run through 20mm plastic conduit? I think I have traced the relay needed (£10 with optional latch link). Shouldn't cost too much extra with the bits I already have & I'll have a spare unused alarm panel

Will start experimenting Monday if I can get the parts.