WEBVTT 00:00.050 --> 00:04.430 This is the solution for the activity eight, where you have to turn on an LED. 00:04.430 --> 00:09.530 If movement is detected and you have to turn it off if there is no movement. 00:09.530 --> 00:12.590 So first of all we are going to import. 00:12.590 --> 00:16.010 So from Gpio zero we're going to import everything we need. 00:16.070 --> 00:18.440 So imports we need the LED. 00:18.560 --> 00:19.460 And then dot. 00:19.490 --> 00:22.070 We need the motion sensor. 00:23.030 --> 00:24.830 All right then what do we need to do. 00:24.830 --> 00:26.540 We need to initialize them. 00:26.540 --> 00:31.460 So LED is equal to LED like this. 00:31.490 --> 00:33.260 And we're going to use the first one. 00:33.260 --> 00:35.450 So should be Gpio 17. 00:35.450 --> 00:36.920 You can use any LED you want. 00:36.950 --> 00:38.900 You can even use several LEDs okay. 00:38.900 --> 00:39.530 It doesn't matter. 00:39.530 --> 00:46.790 And then the peer let's create peer variable with motion sensor Gpio number four. 00:46.820 --> 00:47.360 Great. 00:47.360 --> 00:49.640 And now I'm going to do the solution in two steps. 00:49.640 --> 00:51.860 So that's going to be the same result for both. 00:51.890 --> 00:54.080 It's just different ways to write the code. 00:54.230 --> 00:56.420 And let's start with a while loop. 00:56.420 --> 00:59.600 So what I can do is while true okay. 00:59.600 --> 01:05.450 So we want to do what we want to turn on the LED or turn off depending on if there is a movement, but 01:05.450 --> 01:09.050 we just want to do that as was as long as we run the program. 01:09.080 --> 01:09.290 Okay. 01:09.320 --> 01:10.910 So let's use an infinite loop. 01:10.910 --> 01:14.330 And if I use an infinite loop I'm going to also import time. 01:14.690 --> 01:24.650 And then I'm just going to add a small delay time dot sleep 0.01 just to slow down this loop. 01:24.680 --> 01:26.780 Otherwise it's going to take the full CPU. 01:26.780 --> 01:32.870 And then it's quite simple if pi r dot motion detected. 01:33.920 --> 01:34.040 Okay. 01:34.040 --> 01:35.960 So before we just printed that. 01:35.960 --> 01:40.190 But now we can just do if because you know it's a it's going to give true or false. 01:40.190 --> 01:41.990 So if this is true what do we do. 01:41.990 --> 01:44.630 We do LED dot on. 01:45.110 --> 01:47.450 And then if it's not true it's going to be false. 01:47.450 --> 01:53.060 So we'll just go to the else LED dot off and that's it. 01:53.060 --> 01:55.850 So now I can run the program. 01:55.850 --> 01:57.950 So this time we don't print anything. 01:57.950 --> 02:03.050 But then you see if I put my hand here the LED here is powered on. 02:03.080 --> 02:03.320 Okay. 02:03.350 --> 02:04.760 Put my hand again. 02:05.660 --> 02:06.140 All right. 02:06.140 --> 02:09.210 You see on I keep doing movement. 02:09.330 --> 02:11.400 Maybe I'm a bit too close. 02:11.610 --> 02:11.790 Okay. 02:11.820 --> 02:13.650 That's why we have some issues. 02:13.650 --> 02:15.030 But if I move like this. 02:15.060 --> 02:15.330 Okay. 02:15.360 --> 02:16.290 It's on. 02:17.280 --> 02:18.090 All right. 02:18.090 --> 02:21.930 And then I remove my hand is going to turn off. 02:21.930 --> 02:22.950 And then I put my hand again. 02:22.980 --> 02:25.590 You see there's a small delay before it can go on again. 02:26.280 --> 02:29.490 I remove my hand and it's off. 02:29.580 --> 02:30.210 Great. 02:30.210 --> 02:31.350 So it's correctly working. 02:31.380 --> 02:35.640 And so, as I told you, there are several things that could affect the behavior of the Pir sensor. 02:35.640 --> 02:39.150 For example, if there is too much light, like in my case, I have a lot of light. 02:39.150 --> 02:44.520 And then maybe if you are too close to the Pir sensor, it's better to be a bit more distanced anyway. 02:44.520 --> 02:51.570 It can detect movement up to 3 to 7m depending on one of the potentiometers, so you can do the movement 02:51.600 --> 02:55.080 a bit more far and the result should be a bit more precise. 02:55.080 --> 02:56.670 So that's it for this activity. 02:56.670 --> 03:01.980 But actually we are going to improve the code with what I gave you in the previous video. 03:01.980 --> 03:10.020 So I'm going to actually I'm going to comment that and I'm going to comment import time because we don't 03:10.020 --> 03:11.940 need this as well. 03:12.480 --> 03:12.840 Okay. 03:12.870 --> 03:23.370 And what I will do is I will say that after we initialize the component, I do PR dot when motion is 03:23.370 --> 03:29.790 equal to and I need to give the name of a function that we need to call when motion is detected. 03:29.790 --> 03:32.010 And this function we already have it here. 03:32.010 --> 03:33.690 It's led dot en. 03:33.690 --> 03:35.790 So I put led dot en. 03:35.790 --> 03:42.120 But note and I have already explained that before we don't put any parentheses here because we don't 03:42.120 --> 03:49.230 call the function, we just register the function to be called back again in the future when a motion 03:49.230 --> 03:50.130 is detected. 03:50.160 --> 03:50.400 Okay. 03:50.430 --> 03:51.840 So that's a very different thing. 03:51.840 --> 03:57.600 If I come back to a previous analogy I did, it's like if you give your phone number to somebody that 03:57.600 --> 04:02.310 they call you back when a motion is detected, then you give them, well, your phone number. 04:02.310 --> 04:03.600 They don't call you directly. 04:03.600 --> 04:04.980 They will call you later. 04:05.010 --> 04:05.190 Okay. 04:05.190 --> 04:07.590 So that's what we do here. 04:07.680 --> 04:17.860 And then per dot when no Motion because, well, we want to turn on the LED if there is a motion, but 04:17.860 --> 04:21.040 if there is no motion, we also want to turn it off. 04:21.040 --> 04:24.010 So led off without any parentheses. 04:24.190 --> 04:25.030 And this is nice. 04:25.030 --> 04:30.490 But if we just run the program like this, well, this is doing nothing in its own. 04:30.490 --> 04:35.080 It's just registering a callback, but it's not going to pause the program or anything. 04:35.080 --> 04:37.000 So we need to pause the program. 04:37.000 --> 04:41.290 And I'm going to just do from signal import pause. 04:42.160 --> 04:45.580 And I'm going to run pause here. 04:46.180 --> 04:51.550 And here I use the parentheses because I'm actually calling the function okay. 04:51.550 --> 04:53.800 So here it's registering a callback. 04:53.800 --> 04:55.270 Here we call a function. 04:55.270 --> 04:57.910 And you can see this is it okay. 04:57.910 --> 05:01.150 So the program is smaller and well you can run the program. 05:01.150 --> 05:02.950 It's going to do the exact same thing. 05:02.950 --> 05:06.100 There's almost no difference between those two parts of code. 05:06.130 --> 05:06.520 Great. 05:06.550 --> 05:08.200 This activity is now finished. 05:08.200 --> 05:15.220 And that's also the end of this section on the Pir sensor that we will use again for the final project 05:15.220 --> 05:16.300 of this course.