It's no secret that the alarm system is often mandatory these days. In specialized stores, security and alarm systems cost a lot of money and not everyone can afford it. However, you can ensure your own safety by making a simple alarm with your own hands.
We offer to start the production of alarms by viewing the author’s video material
So we need:
- Motion Sensor;
- transistor NPN;
- 10 kΩ resistor;
- home call;
- volume control;
- power button;
- soldering iron.
The motion sensor has 3 outputs: a short one is +5 volts, a medium one is a 3.3 volt output and one common wire. According to the author of the idea, such a sensor can be purchased on the eBay website for about a dollar. We also note that the volume control is not an obligatory component of the design.
First of all, we present to your attention a scheme of future signaling to facilitate understanding of the design.
We disassemble the doorbell. It is necessary to unsolder the wiring that goes to the positive contact of the battery compartment.
The transistor has 3 pins. The right one is the base, the middle one is the collector, the left one is the emitter. The emitter needs to be soldered to the wiring, which we soldered from the plus in the previous step.
Now we take the resistor that needs to be soldered to the middle wiring of the motion sensor.
The second end of the resistor is soldered to the base of the transistor.
The wire on the sensor with the designation "Ground", that is, ground, is soldered to the minus in the doorbell.
We lengthen the shortest wiring on the sensor and solder to the plus in the call. Note that you need to solder the wires with the batteries removed.
Now the solder of the transistor is soldered to the plus by connecting with a piece of wire.
The circuit is almost assembled. It remains to shorten the wiring between themselves, which by default go to the call button. Do not forget to isolate.
The motion sensor has two resistors. The first one, which is located on the right side of the author’s sensor, adjusts the time of the output signal after the sensor starts working. The left adjusts the response range - from 2 to 5 meters.
We collect the call. Install the batteries. Alarm works according to the following principle.When an object appears in front of the motion sensor, the sensor transmits a signal to the doorbell, which in turn starts to make a sound. In the end, we note that when using the power button, the following should be borne in mind. turning on the alarm, it will begin to work, however, the doorbell emits one signal, after which the alarm starts to work as intended.