Hi i really am a newbie and need some advice.

i have a pir floodlight which lights on when theres movement outside.

I want to install/build something that makes an audible noise when the light goes on.

BUT only for a set time amount e.g. 5-10 seconds.

my original idea was to use a relay and have a small dc circuit to kick in with the buzzer.

but not sure how to do timing ?

any help/advice is appreciated

 

R1 = 10k
C2 = 1nF
The IC is a NE555N.
C1 and RA can be calculated using the formula which can be found on the datasheet of the 555.

RL is your siren which can be purchased as a ready built module, just check it uses less than 200mA or you'll need a transistor to buffer it.


The above picture is an attachment used in another thread so you won't be ab;e to see it unless you're logged on.

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Also, the PIR sensor runs on 5 volts, the relay inside the unit I took a part was 12 volts. You can take power off the relay coil terminals to power your timer/buzzer.

 

hi,
The OP should be aware that the electronics and 5V and 12V supplies internal to the PIR are most likely NOT mains isolated.

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Eric
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It's also possible that they aren't capable of providing the required current.

I've dismantled a PIR before and it did have a transformer but it was very small, 1.5VA at most and certainly not powerful enough to power a siren.

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hi,

I agree about the current capacity, the ones I have dismantled have the Line series capacitor, about 0.22uF thru 0.47uF.

I have found the best way, is to wire a short mains extension lead across the lamp terminals, they are accessable on the terminal block
Terminate the extension lead with a 'free' socket and just plug in a low voltage adaptor,, it gives the current and isolation.

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Eric
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PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

hi

its a 300w floodlight.

so the pir sensor is not powerful to power the buzzer?

just to make sure i should

take the power from the wires that go to the floodlight (probs 230v)

and somehow connect it to the timer and buzzer?

the buzzer is only 3v that i want to power.

confused! lol

 

How much current does it draw?

The buzzer can be powered from a small mains transformer and a bridge rectifier connected in parallel with the halogen.

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lol

i haven't even bought the floodlight yet.

either a 150w or 300w one, unless theres one that you recommend!

is there any way to make the buzzer sound nice and calming and not like a siren?

thanks

 

hi,
Look at this sketch.

A 150W or 300W depends upon the area you want to light up.

Do you follow.?

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Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Hey

Thanks for the diagram! i understand it a lot better now!

i'm going to use a 300w one.

After i connect a 12v dc plug into the socket.

then i just need to make the 555 timer with the buzzer?

am i right

thanks again

 

hi,
When you have the socket wired into the PIR's terminal block, it gives you a mains socket in which you can plug in a 12Vdc adaptor.
The length of the mains cable between the PIR and the extension socket can be many metres.
Be SURE to use mains rated cabling.!!!!

The 12Vdc output from the adaptor can be used to drive a 555 configured as a Monostable for a 10 second timing period which can drive a buzzer or bleeper.

Choose an adaptor that gives a regulated 12Vdc output at say 300mA [or higher] this should be good enough to drive most projects.

OK,?

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Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Hi

thanks again, i think i know what i'm doing

btw cant i use standard lighting cable as its thinner than mains cabling?

I have an outside standard 60w bulb box and thats connected through the lighting circuit (5amps).

my plan was to take the bulb box off and place the floodlight in its place.

so therefore i shouldnt need to use 2.5mm cabling (mains cabling). i could get away with lighting cabling. the main reason i want to use it

a) its flexible
b) its thinner
c) looks more appealing! lol

what do you think?

 

hi Ali,
I dont mean the 'solid' type of mains cabling, I mean 3 core mains voltage cable, rated at say 3Amps.
The same type as used on domestic appliances, dont just use for example, single insulated equipment wire.

OK.?

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Eric
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PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Please be more descriptive, what do you mean by a calming sound?

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