How to Build Your Own Motion Detection Sensor

What You'll Need
1 Poly Block
1 PIR sensor (Passive InfraRed sensor)
1 alarm
1 battery
1 clip
AWG wire
Measuring tape

Learning how to make your own motion detection sensor is very useful and practical knowledge to have. Your previous understanding of electrical concepts, and a type of sensor you want to install, will determine how fast you will have your final product ready. In any case, building it on your own is not that complicated if you choose a simple model, and it will give you some additional peace of mind when it comes to protection of your property, values, and loved ones.

Sensors use infrared light, laser, vibration, frequency, or sound as detectors, and as their name implies, they detect changes in the area they cover, and send a signal, triggering the alarm, if somebody enters the space you want to protect. The focus here is on the simple motion detection sensors that use infrared light, which you can easily build on your own with basic materials available at the regular supply stores.

Step 1. Preparation

Decide where you want to mount your detector and measure the size of the area you want to cover with a device you are about to build. If you are not sure what strength of battery and alarm you need, ask for advice in the electrical store where you buy the necessary materials. The same goes for the AWG wire, since diameter of the wire is important. Buying a PIR sensor is much easier than making this most sensitive part from scratch. They are energy savers and not expensive. Ask in the store what model will suit your needs.

Step 2. Connecting Components

Connect the battery, poly block and sensor. First, connect a positive wire from the battery’s clip (look for the sign +) to the positive poly block’s spot. Now connect the negative battery’s wire to the 0 spot (usually 0v) on the device. Now, connect a sensor to the poly block. Following the R-B-Y wire rule, all you want here is to apply 5-0-2 input combination: red wire from the sensor goes to input 5 of the poly block, black one to 0v spot, and the yellow wire to 2v.

Step 3 . Setting the Switch

Poly blocks have switch outputs, and all you need for your motion detection sensor is to set the output on 0010. That way you make sure that the alarm will be on when the person or “the object” that triggered the alarm leaves the area covered by the sensor.

Step 4. Connecting Alarm

The alarm gets connected to the poly block by attaching the positive alarm’s lead to the positive connection spot of the device, and the negative lead to the poly block’s S0 spot. To power your own detector, connect the battery, and that is it.

Step 5. Adjusting Your Device

Once the building part is over, you can determine for how long you want the alarm to go when it detects the motion. The available range goes up to 10 or 15 minutes and you can set your amount of time by turning a resistor of the poly block to desirable length.


You can replace the alarm with a buzzer and in that case the procedure is the same. If you don’t like noise, use a light bulb but make sure that the light and battery operate at the same voltage.