12V PIR to switch 12V lights

[JB]

Are there any suppliers of such devices?

[PC Paul]

[PC Paul]

1/10 the price...

[PC Paul]

After 2 duff £100+ links, how about this for £49.95?

seems an awful lot though.

[Owain]

Standard intruder alarm PIR, with a 12V relay (car headlight or starter motor relay?) to switch the high-current load.

An intruder alarm PIR probably won't switch the load directly.

Owain

[Rob Morley]

Can you not just use a mains PIR to switch the 12V transformer?

[Andrew Gabriel]

Intruder alarm PIR will only latch on for a second or two. You would probably need some extra logic to latch on for a reasonable time period. Also, might want some logic to prevent it operating unless it's dark.

[JB]

No mains available without digging up 100ft of garden, just a 12V battery which I will charge periodically.

Rob Morley wrote:

[Bob Mannix]

You could purchase a caravan inverter to provide 240V.

[Christian McArdle]

That would drain the battery very rapidly.

Christian.

[Grunff]

You'll need to use it to drive a suitable relay, such as:

[Dave Plowman (News)]

Maplin do a kit which runs off 12 volts.

[Dave Plowman (News)]

[manatbandq]

Why?

The battery capacity is the same for a given load, 12V at n amps or

240V at n/20 amps less some for the inefficiency of the inverter.

MBQ

[Grunff]

This is the problem - the inverter inefficiency. For most inverters this is highest at low loads, and especially so for cheap inverters, which can have a no-load draw of 10-20% of their total capacity.

Besides, doing this with an inverter and 240V is just plain silly - it would be much easier and cheaper to knock up a 12V system.

[Christian McArdle]

Because it will draw loads of current when off, unlike a 12V PIR sensor.

Christian.

[JB]

Thanks for the replies - seems that there isn't an off the shelf product.

[JB]

Actually I found what I wanted...

Its a R> Thanks for the replies - seems that there isn't an off the shelf > product.