PIR security light to activate an additional strobe???

[linners]

I'd like to use my PIR security light to activate a remote strobe - what would be the easiest/cheapest DIY project for this?

I might want to go on and have a siren on a delay with this set as well

Thanks in advance with any help/advice

[Thomas W]

What kind of output does your PIR security light have? Relay or voltage, or?
Remote, is that by wire, or wireless? And how far?
What kind of power source do you want to use for this new project? I assume the security light is always on, connected to the mains.

[linners]

I'll have a look at the output and get back to you. It's only a "budget" mains powered PIR light so nothing fancy - not sure if that's an indication as to what type of output it might be?

The idea behind this project is that I want the PIR light to activate when I enter my garage via the vehicle entrance and activate immediately so I can see where I'm going before I switch my normal lights on. Ideally I'd like the strobe to activate after a short delay but this isn't too important - I can switch it off manually so that the PIR can be used independently. The remote strobe will only be for external notification that the PIR has been triggered and will be only a few meters away at the most
The siren will have to go on a delay or I won't be too popular with the neighbours every morning and evening (And they'd probably ignore if my garage did get broken into....)


Thanks

[Thomas W]

I have a PIR light from a DIY shop that has a relay in it, for mains voltage output.
The 555 timer IC can be used to create a time delay: http://en.wikipedia.org/wiki/555_timer_IC
I can be powered by a general mains adapter/transformer.
Do you want to build your own strobe light and siren, or buy? There are DIY kits for both circuits. Or you could do the wiring yourself. How much power do you want? (Light, sound)

[linners]

Was looking at an external strobe similar to this:

http://www.ebay.co.uk/itm/280774030131? ... 1438.l2649

and a horn for inside the garage like this to make it uncomfortable for any intruders to be close to:

http://www.ebay.co.uk/itm/NEW-CAR-ALARM ... 20bee6f8b8

[Thomas W]

The strobe light draws 200 mA at 12 V, which could be switched with a transistor.
The horn uses 20 W at 12 V, that is
I = P / U = 20 W / 12 V = 1.7 A
which could be switched with another transistor.

[linners]

All sounds very do-able....
What would be the best way of achieving this?
I'm going to use a spare car battery that I have to provide the 12V DC supply to the horn and strobe. I'll keep an eye out on the charge periodically to make sure it doesn't drop too low a voltage
Thanks for your advice so far

[Thomas W]

Here's an idea for the horn:

I'm assuming that your PIR relay is Normally Closed (NC). Then the voltage across C1 is normally 0 V, short circuited to GND. When the voltage on the B pin (base) of T1 is 0 V then T1 is OFF and pin 2 on IC1 is high through R2, causing pin 3 to stay low.
When the PIR relay opens, current starts to flow into C1 through R1, causing the voltage on the B pin of T1 to go up and opening T1, so that pin 2 on IC1 drops and triggers an output high on pin 3, turning T2 and the horn ON.
S1 is the reset switch.
Something similar could be used for the strobe, if you want to delay it too.