!2 volt alarms ?

[timthegas68]

I'm looking for an alarm system to install in a articulated trailer that has
been converted to motorhome use on top deck and workshop on lower deck.
The only way into it is a side door.
There are some sliding windows on the upper deck too if an intruder was keen and had a ladder.
There is no mains electricity where the trailer is parked.
I am looking for an alarm for the door and some PIR's also but it needs to be run off a 12 volt battery and also have back up battery also.
I would want some sort of visual deterent outside near the door - strobe light or something and a few loud sound bombs to make as much noise as possible to alert the night watchman security guard if an attempt at entry was made.
There are 2 large truck type 12 volt batteries inside the trailer for the tail lift already so the power source is there.

Does anybody make such as system or can one be made up ?

I have installed similar alarms in previous workshops, garages and outbuildings in the past but they all had a 240 volt supply.
So looking for 12 volt only stuff.
Appreciate if anyone can advise me on this or have any recommendations.

Thanks , Tim.

 

[sparkymarka]

Most alarm panels are 12v so that's not a problem in the old days you could use a logic 4 key switch panel as they could also use 9v dry cell batteries. You can still get a alarm module which runs off 12 v and use with a key switch.

 

[timthegas68]

Most alarm panels are 12v so that's not a problem in the old days you could use a logic 4 key switch panel as they could also use 9v dry cell batteries. You can still get a alarm module which runs off 12 v and use with a key switch.

So if most are 12 volt, do they have mains 240 volt run into them and then internally they must have a 240V/12V transformer rectifier.
To reduce voltage and convert AC current to DC ?

 

[EightyTwo]

Yes they do.

Then they have a couple or three voltage regulators to provide the 12V power to bell, keypad, PIRs, etc. And 5V for the circuitry. They also have a battery charging circuit and the wherewithall to use the battery in the event of mains failure.

In general, you may have trouble running one from a 12V source as the transformer output is usually 15-18 VAC to allow for a batery charging voltage of 13.8V. You might be able to just run the board from the battery connections and ignore the 'mains fail' fault message... Alternatively, you could try a 12 to 15V DC-DC convertor first.

Personally, I'd try running the thing from a little 12 to 240VAC inverter. You're unlikely to need more than about 25 watts and, although it's going to be really inefficient, it will be cheap and simple.

 

[timthegas68]

I might just put a big fook off steel bar across the side door and use some
serious padlocks to prevent it from being jimmyed open.
I've just had the ****** visit me and nick all my diesel out of the tractor unit so am concerned they might come back and break in.
I don't have anything valuable in there as all my tools etc are at home for the winter.
Just concerned they would wreck the side door. It cost me £1200 to have it installed so not cheap if some fooker busts it open.

 

[sparkymarka]

Have a look at this on ebay. 350939386810 Use this with a bell timer and a keyswitch to make a simple alarm...or better still look for a logic 4 sure I've seen on ebay...

 

[ekmdgrf]

Just run 12V from the tail lift batteries to the panel. I'm not sure there's a lot of point in connecting up a battery backup for a battery power source. There's not a lot that can go wrong with a piece of wire connected between a battery and a circuit board. Except maybe the battery goes flat, in which case you're just delaying the inevitable. If you're really keen, as you mention two batteries, you could run one to the 12V in and one to the battery in? I'm assuming the tail lift batteries get charged at some point?

 

[EightyTwo]

Just run 12V from the tail lift batteries to the panel.

Some panels will object to this - they need "mains" AND a battery or they'll give you a fault... You won't be able to clear the fault or set the alarm without some careful bodgery. Hence the inverter suggestion...