Hi, this is Wayne again with a topic “Resistance-Controlled Alarm”.
This week, i’m going to show you how to make a portable alarm system that’s controlled by resistors. The basic design of this alarm is very simple: a motion sensor detects when someone walks into the room when an intruder is detected, it activates a siren, but what makes this system unique is that it’s activated and deactivated by touching a certain value resistor to a pair Of metal contacts on the housing, the brains of this system is an arduino microcontroller. So the first thing that you need to do is go to the project page and download a copy of the example code. Then upload it to the board, now you’re ready to start connecting all the other parts. The easiest way to do this is with a prototyping breadboard.
The motion sensor needs to be connected to ground 5 volts and digital pin 13.. The piezo buzzer is connected to ground and digital pin 2.. The last parts to connect are the resistors. The two resistors are wired in series to form a voltage. Divider one end is connected to 5 volts and the other end is connected to ground. The center connection between them is connected to analog. Pin 5. now remove one of the resistors and turn on the power.
The system will start up in standby mode to arm and disarm the system. All you have to do is briefly reconnect the resistor to the breadboard after testing the system, you’re ready to solder all the parts together to do this. I took a small piece of perf board and i made a simple diy proto shield. All the external components are soldered to the perf board and the perf board has a set of pins that attach directly to the appropriate pin holes on the arduino. Once everything is assembled, you’re ready to mount it all inside a project, enclosure drill, a three quarter, inch hole in the front of the housing for the motion sensor then drill a quarter inch hole in the back side of the housing for the buzzer. On the top side, drill two more holes for the resistor contact, screws, hot glue, the motion sensor and the buzzer to the inside of the housing attach the machine screws with a pair of nuts, then connect the resistor jumper wires to the screws and add another pair Of nuts to hold them in place, lastly, fit the arduino inside the housing and close it up.
Now, your alarm system is complete. Set it up in an area that you want to protect, then touch your key resistor to the screw contacts to arm the system. Whenever the system detects motion, the siren will go off to deactivate the alarm just touch the resistor to the contacts for two seconds.
This delay prevents the system from being hacked with a potentiometer. If you want to make the resistor key extra secure, you can cover up the color indicator, stripes with markers or paint. Well, that’s how to make a resistor controlled alarm system thanks for watching and check back next week for more diy hacks and how to’s you .