WEBVTT 00:00.080 --> 00:06.260 Now that you have added the Pir sensor to your circuit and you have pulled on your Raspberry Pi, then 00:06.260 --> 00:10.550 you can connect back to VNC or whatever you use to get access to the Raspberry Pi. 00:10.550 --> 00:15.500 And let's write some Python code to detect a movement with this sensor. 00:15.530 --> 00:17.810 The first thing to note is that this sensor. 00:17.810 --> 00:22.610 So after it's powered on, it needs about one minute to be initialized. 00:22.610 --> 00:25.220 So try not to run anything in the first minute. 00:25.220 --> 00:30.350 And actually it doesn't mean the first minute after you open here, for example, Sony, but the first 00:30.350 --> 00:32.870 minute after you just power on the Raspberry Pi. 00:32.900 --> 00:37.730 So by the time that the Raspberry Pi is powered on, that it connects to the Wi-Fi and that you connect 00:37.730 --> 00:40.040 to it, it's probably almost a minute. 00:40.040 --> 00:40.880 So it should be fine. 00:40.880 --> 00:42.800 But that's just one thing to keep in mind. 00:42.800 --> 00:46.160 So how to control the Pir sensor. 00:46.190 --> 00:49.700 Well we are going to use the Gpio zero library. 00:49.700 --> 00:52.370 So I'm going to do from Gpio zero. 00:52.490 --> 00:55.550 And we have seen already LED and button. 00:55.550 --> 00:57.830 And there is something else. 00:57.830 --> 01:03.630 So there is another functionality for this sensor and it's called motion sensor. 01:03.660 --> 01:04.260 Like this. 01:04.290 --> 01:04.500 Okay. 01:04.530 --> 01:06.690 With M and S uppercase. 01:06.690 --> 01:09.750 So this is the functionality for the Pir sensor. 01:09.750 --> 01:11.130 And then to initialize it. 01:11.130 --> 01:12.450 So let's create a variable. 01:12.450 --> 01:18.030 Let's name it Pir for example is equal to motion sensor. 01:18.030 --> 01:21.090 So it's the same thing as we did for the push button for example. 01:21.090 --> 01:23.100 And we need to give the Gpio number. 01:23.100 --> 01:25.500 So Gpio number is going to be four. 01:25.500 --> 01:27.600 And what this is going to do. 01:27.600 --> 01:32.190 Well it's going to initialize the Gpio four as an input pin okay. 01:32.190 --> 01:35.490 Because we want to read data from the Pir sensor. 01:35.490 --> 01:37.440 So now this is an input pin. 01:37.440 --> 01:39.930 And then basically what we want to know is quite simple. 01:39.930 --> 01:43.350 We want to know if there is a movement or if there is not a movement. 01:43.350 --> 01:49.260 So we have a simple attribute we can do Pir dot motion detected. 01:49.770 --> 01:51.420 And here there is no parentheses okay. 01:51.420 --> 01:54.540 It's kind of a variable inside the Pir. 01:54.570 --> 01:58.260 So this is going to tell us if a motion is detected. 01:58.260 --> 02:00.440 So I can print that, for example. 02:02.270 --> 02:08.390 And actually it's going to be better if we can print it continuously and then see what's happening. 02:08.390 --> 02:11.900 So instead of just printing it once and then having to run the program again. 02:11.900 --> 02:15.200 So I'm going to do the same thing we did for the push button previously. 02:15.200 --> 02:16.370 So it's not new. 02:16.370 --> 02:17.930 So I'm going to go quite fast. 02:17.960 --> 02:24.290 I can do infinite loop and I just print the value here which is going to be true or false. 02:24.290 --> 02:30.590 And also because what it's going to go very fast, I'm going to add import time. 02:31.790 --> 02:40.100 And I'm going to do a time.sleep with, well for example 0.01 second. 02:40.100 --> 02:43.460 So we run this 100 times per second okay. 02:43.490 --> 02:44.840 That's going to be very fast. 02:44.840 --> 02:46.160 We don't need more than that. 02:46.160 --> 02:47.960 And it's going to save a lot of CPU. 02:47.960 --> 02:50.420 And with this well with this that's it. 02:50.450 --> 02:51.620 We can run this code. 02:51.620 --> 02:55.280 And we're going to see if the movement is detected or not. 02:55.370 --> 02:57.090 And here's the secret. 02:57.090 --> 03:02.700 So you see, I have put my sensor here on one side so that we can detect movement on that side here. 03:02.700 --> 03:07.110 So when I try to detect a movement I'm going to move my hand here. 03:07.140 --> 03:10.230 One thing to note is that I have a lot of light coming here. 03:10.230 --> 03:16.290 So if you have too much light it could influence the result and you might have some false positive. 03:16.290 --> 03:20.610 So try to put this sensor not too close to a light. 03:20.640 --> 03:27.090 I'm using a lot of light here for well to grab and to record this setting, but just know that it can 03:27.090 --> 03:28.260 have an impact. 03:28.260 --> 03:31.320 So let's run this. 03:31.320 --> 03:32.910 And you see it's going to be false. 03:32.910 --> 03:34.350 So no motion is detected. 03:34.350 --> 03:36.180 Now I'm going to put my hand like that. 03:36.180 --> 03:38.520 And you see it's true I remove my hand. 03:39.060 --> 03:41.040 It's still true for some seconds okay. 03:41.070 --> 03:41.970 That's what I told you. 03:42.000 --> 03:42.900 There is a delay. 03:42.900 --> 03:47.760 So when a movement is detected, the sensor is going to output high. 03:47.790 --> 03:53.220 So here we're going to read motion detected for a few more seconds okay. 03:53.250 --> 03:55.500 So that's the potentiometer we have set. 03:55.500 --> 03:58.220 And then one other things I want to show you is that. 03:58.220 --> 04:02.390 So I'm going to put my hand, I remove my hand and then I put my hand again. 04:02.690 --> 04:05.390 And you see that there is a delay. 04:05.390 --> 04:11.870 So after we go back to false, after the motion is not detected anymore, there is a delay so that the 04:11.870 --> 04:14.960 sensor is going to read a positive value again. 04:14.990 --> 04:15.200 Okay. 04:15.200 --> 04:17.780 And this delay is about 2.5 seconds. 04:17.780 --> 04:23.060 So very basically if it detects a movement okay it's gonna you're gonna get true here. 04:23.060 --> 04:25.550 Then if it goes back to false. 04:25.550 --> 04:26.960 So there is no movement detected. 04:26.960 --> 04:30.290 After some seconds it's gonna go back to false. 04:30.290 --> 04:35.750 But before it gets back to true again it needs to wait 2.5 seconds minimum. 04:35.780 --> 04:36.110 Okay. 04:36.140 --> 04:40.520 So there is a second delay between two movements that can be detected. 04:40.520 --> 04:46.310 And finally, the last thing I want to show you is if I move here and I continue to move okay. 04:46.340 --> 04:51.350 Well we have a we have a problem with the reading here, but let's say okay, I move, I continue to 04:51.380 --> 04:55.380 move and you see that it's still true. 04:55.380 --> 04:57.030 And then I remove my hand. 04:58.500 --> 05:05.460 So as long as I keep doing movement in front of the Pir sensor, it's going to give us true here in 05:05.460 --> 05:06.120 the code. 05:06.120 --> 05:13.230 And this is because of the jumper that we set in the high position, which means that as long as we 05:13.230 --> 05:18.630 get some movement detected, the Pir sensor is going to continue to output high. 05:18.660 --> 05:18.900 Okay. 05:18.930 --> 05:20.010 For the delay. 05:20.010 --> 05:26.460 So for the 3 to 5 seconds minimum that I told you so for 3 to 5 seconds is going to basically reset 05:26.460 --> 05:28.860 the delay every time that the movement is detected. 05:28.860 --> 05:34.890 If you were to use the low position, then after those 3 to 5 seconds, then the reading will directly 05:34.890 --> 05:38.100 go back to false, even if you keep doing movement. 05:38.130 --> 05:38.340 Okay. 05:38.370 --> 05:40.080 So that's that's the difference. 05:40.080 --> 05:43.320 But basically you can see we have lots of different delays. 05:43.320 --> 05:46.800 So just try to experiment on your own and see what it does. 05:46.800 --> 05:52.320 So if the data you get is completely unreliable, well make sure you check your circuit again. 05:52.320 --> 05:53.840 So you might need to power off. 05:53.840 --> 05:57.260 So you might check the circuit or the potentiometer or the jumper. 05:57.260 --> 06:00.770 But if you followed carefully the instructions it should be okay. 06:00.800 --> 06:06.020 All right so to recap here you need to import the motion sensor from Gpio zero. 06:06.050 --> 06:08.900 Then you initialize the motion sensor. 06:08.930 --> 06:10.370 You can create a variable. 06:10.370 --> 06:14.480 And then with motion detected it's going to give you true or false. 06:14.510 --> 06:19.670 And if you put your so if you do some movement in front of the sensor it's going to give you true. 06:19.670 --> 06:25.280 And then depending on the potentiometer that you set for the delay is going to return true for a certain 06:25.280 --> 06:26.180 amount of time. 06:26.180 --> 06:31.880 After this amount of time, if there is still movement, then as long as there is movement, it's going 06:31.910 --> 06:32.390 to reset. 06:32.390 --> 06:39.800 Basically this delay and after this goes false, so after no motion is detected for some amount of seconds, 06:39.800 --> 06:41.720 then it's going to go back to false. 06:41.720 --> 06:47.660 And before it can go back to true, there is a delay of about 2.5 seconds that you also need to be aware 06:47.660 --> 06:47.990 of. 06:48.020 --> 06:52.130 Okay, so you are not surprised about the behavior of the Pi sensor.