For a while I had a battery operated motion sensor/alarm device outside on my deck. I did a great job detecting the presence of my dog when he wanted to come back inside. This allowed me to keep the door shut, keeping the flies out and the cold out. I rewired the pizo output to sound inside the house so I could hear it.

But two things were issues...

1) the alarm was constant as the dog continued to move
(Ideally, I'd like it to sound for a couple seconds every 20 sec)

2) the device was cheap and decided not to function well if the humidity was
too high.
(Ideally, this time I want just a water tight sensor outside and the remaining
electronics inside powered by a 5V wall supply)

So my objectives are as followed.

Detect the dog at the door.
Alarm sounds for a couple seconds
Alarm is silent for 15 sec
If motion is still present repeat the cycle

The specs on the PIR are:
Working voltage: DC 4.5-20V
Static current: <55uA
Electronic level output: High 3.3V/Low 0V
Trigger mode: Repeated triggering
BLockade time: 2.5S
Detective angle: <100°
Induction distance: less than 3m
Working temperature: -20---+80

I will need multiple 555's and be able to trigger with a +3.3V

I have no starting circuit yet, but will be working on it today.

The output will be a Pizo(i think) from a old smoke detector.

Thanks

i

 

Do you need something like this ebay

 

Do you need something like this ebay

Yes, that is sort of what I need. BUT!!! That's what I had....cheap Chinese junk, and it didn't last in the harsh Vermont winters, covered from the elements.

 

OK the if you use a pir module like this, and connect your 555 timer with a transistor buffer to trigger it to your desired time, you will need to put it in a weatherproof container.



555 how to use

 

There are a number of ways to approach this. I've come up with a rather simple one to make things easy. The schematic below is for a 555 in astable mode with a low duty cycle. When motion is detected, pin 4 goes high turning the 555 on. The 555 will output ~2.3 second pulse, wait ~15.4 seconds, then repeat for as long as motion is detected. I've shown a 6VDC buzzer attached to the output. If you prefer to use a piezo, we'll need to add another 555 to generate a ~3kHz signal to drive the piezo.

Note I reference a Parallax PIR sensor, Rev. B. RadioShack used to sell this, but now carries their own brand which is designed to work at 3.3V or 5VDC. If you decide to use a PIR other than the one I call out, but mindful you may need to step down the voltage from your power supply. Since PIR sensors do not require much in the way of current, this can be accomplished with a Zener diode and a resistor.

If the buzzer you decide on requires more than ~100mA, you'll want to use a transistor between the 555 and the buzzer.

Hope this helps and let us know if you have any questions.

 

Is the specified "Blockade Time" the time the PIR stays triggered, or the minimum interval between successive triggerings?

 

OK the if you use a pir module like this, and connect your 555 timer with a transistor buffer to trigger it to your desired time, you will need to put it in a weatherproof container.



555 how to use

Thanks Dodgydave, this is the kind of PIR I already have and do intend on making it water-PROOF.

There are a number of ways to approach this. I've come up with a rather simple one to make things easy. The schematic below is for a 555 in astable mode with a low duty cycle. When motion is detected, pin 4 goes high turning the 555 on. The 555 will output ~2.3 second pulse, wait ~15.4 seconds, then repeat for as long as motion is detected. I've shown a 6VDC buzzer attached to the output. If you prefer to use a piezo, we'll need to add another 555 to generate a ~3kHz signal to drive the piezo.

Note I reference a Parallax PIR sensor, Rev. B. RadioShack used to sell this, but now carries their own brand which is designed to work at 3.3V or 5VDC. If you decide to use a PIR other than the one I call out, but mindful you may need to step down the voltage from your power supply. Since PIR sensors do not require much in the way of current, this can be accomplished with a Zener diode and a resistor.

If the buzzer you decide on requires more than ~100mA, you'll want to use a transistor between the 555 and the buzzer.

Hope this helps and let us know if you have any questions.

elec_mech,
Very nice. I thought I'd need two 555's for the timing aspects alone. I do have 556's also and can
use one to generate 3Khz signal.

Is the specified "Blockade Time" the time the PIR stays triggered, or the minimum interval between successive triggerings?

Alec_t,
Honestly, I do not know the answer....didn't even know what "Blockade Time" was...


Update:
I was in the process of disassembling the existing "faulty" motion sensor device so as to isolate just the PIR sensor section and place it alone outside.

The PIR was on a separate 1-by-1in board but contains seems to require 5 wires to interface (Vcc, Gnd, and three outputs). Don't know if all three outputs are being used or not. I was going to use a flexible telephone line (phone to wall type) for wire, but the one I have has only 4 wires in it.

Seems to me that building it will be simple enough.

 

Elec_Mech,

Thanks for the circuit. Oddly enough, this is pretty much exactly the same circuit I used to build a "mole chaser" that I buried in the back yard. See what happens when you don't use the knowledge you have.......gone!

 

See what happens when you don't use the knowledge you have.......gone!

Tell me about it - I'm now keeping a binder of all the really useful things I learn here so I can quickly refer to them later.