I need a circuit idea for a burglar alarm with components being limited to the following. The alarm should be triggered by the IR proximity sensor and stay on till someone disconnects the supply. [edit]All this without an arduino or any controller[/edit]
IR Proximity Sensor - 1 (Gives a digital output)
Caps + Resistors - As Required
Transistors - 2 (any combination)
LED - As Required
9V Battery
7404 - 1
7805 - 1
Buzzer (6 - 12 Volts) - 1
Is it possible to achieve this with this set of components? I've been breaking my mind..
This is for the kids electronics program i'm developing.
The list you gave should be more than enough (you can build a standalone device using these components) if you are using an Arduino. Any particular thing that you are looking for though?
I've see something like this done in a BASIC Stamp book. Here is a link to the pdf of the book on Signals. Go to page 89/137 for IR input and how it uses PWM. I WILL POST THIS LINK NEXT POST - The code is very short but in BASIC - so you will need to try to get it into Wiring. It don't even think your need all of those parts. I would:
START:
Have the IR Emitter connected to an output pin that is pulsing out a freq
The IR receiver connected to an input pin and that is determining if the input coming in is high or low.
Loop back to START if the signal received is HIGH
else if the signal received is LOW send an output signal at another pin connected to your Piezzo Buzzer.
It seems to me that all you may need is the IR sensor, the buzzer and then a few resistors. If the buzzer needs higher than 5V volts you may need that 9V battery, a transistor and a few resistors. I would just see if the buzzer works getting a high voltage outputted from a pin.
I would really recommend you look at that link I sent you. The book is entirely free to download from parallax's website. Hopefully the psuedo code I sent you will help.
A PIR detector is quite different from an IR emitter & IR receiver setup.
An IR emitter and IR receiver could be used to make a 'magic beam' which would detect something blocking the beam.
A Passive Infrared (PIR) Detector detects small differences in temperature.
PIR detectors are used to detect slightly temperature differences, for example something warm compared to its surroundings, which detects a persons body temperature.
The implementation is much easier than I realized since it is just a PIR sensor. The PIR will send a high or low signal to the Arduino input pin. If signal is high the PIR has detected motion. Then output a high signal to your buzzer connected to an output pin.
If there is no Arduino then the application is quite simple. Your PIR is going to produce a high voltage out when motion is detected. The output voltage from the PIR can just connect to the base of an NPN transitor. Which will then open the transistor to the emitter which you would have your buzzer connected to. Here is a rough schematic. http://picasaweb.google.com/lh/photo/o3Q7wgP009NKe7nlSZxipz2qwst-Qvyrn_-T3i-6zWM?feat=directlink. I don't see why that shouldn't work. Anyone disagree? You are going to have to play with the resistor values.
Your PIR is going to produce a high voltage out when motion is detected. The output voltage from the PIR can just connect to the base of an NPN transitor. Which will then open the transistor to the emitter which you would have your buzzer connected to.
Well i want the buzzer to stay on even after the PIR goes low. Say a burglar has triggered the alarm shouldn't it hold till it is put off?
Here is another schematic then.http://picasaweb.google.com/lh/photo/k5cWgoCDzPIL3k5zubNA8T2qwst-Qvyrn_-T3i-6zWM?feat=directlink I believe eventually the signal will die out and will fade as time goes on. I have just built the circuit and it works perfectly. I have been waiting for 15 minutes and the signal has still not gone out. Instead of unplugging the supply I would suggest you just put a push button across that shorts the capacitor terminals together so it can drain instantly and shut off the signal. If you really wanted it to shut off by removing the power source alone i don't know if that would work for this setup. You would need to wait for the capacitor to drain. I think the push button is just more convenient than having to unplug the supply.
Thanks a Ton! Wondering if you drew those circuits? i was thinking there was a possibility like this but couldn't translate it. I was trying with a single transistor.
Yeah I drew both of those. Also change the resistor on the second transistor/buzzer portion, the one from the 9 v supply to something lower for a louder effect. Let me know if you need anything else.
thanks for the effort mate! let me know if you have any other circuit ideas that kids can try out with an end application in mind. these need to be simple with basic components.
What value did you use for the capacitor? I tried with a 2200uf and it seems to be on only when the IR sensor is detecting something after that it goes off. I used 2n2222A transistors. :-/
