WEBVTT 00:00.330 --> 00:05.620 Let's now get the distance from an obstacle using ultrasonic sensor. 00:06.030 --> 00:08.510 So now you know basically how it works. 00:08.520 --> 00:13.740 And with this code, you will clearly understand what I previously explained in the last lesson. 00:14.070 --> 00:16.910 And then what you can do is watch, begin to listen. 00:17.070 --> 00:19.230 So everything will be super clear for you. 00:19.530 --> 00:25.170 So what we are going to do here is to print the distance we get from the ultrasonic sensor to these 00:25.170 --> 00:25.690 saleman. 00:26.190 --> 00:28.120 So how to start the program? 00:28.320 --> 00:35.290 Well, why not start by using define for the two digital pings we are going to control? 00:35.730 --> 00:41.940 So we have equal theme, which has been number three and define. 00:45.440 --> 00:47.700 In which he's been number four. 00:48.200 --> 00:50.810 All right, in the setup, I'm going to do. 00:51.890 --> 00:54.920 Most childhood begin. 00:56.720 --> 01:01.970 OK, where does moderate and then pink mold, so Echobrain. 01:04.650 --> 01:13.990 Needs to be set up as a input, be OK, because we are going to read from that B and then Pink Moon 01:14.550 --> 01:15.330 trigger happy. 01:18.490 --> 01:25.030 Is up because this is the pain we are going to use to communicate to the ultrasonic sensor. 01:25.300 --> 01:25.750 All right. 01:25.750 --> 01:27.910 And our setup is good. 01:28.240 --> 01:32.980 Now, what we're having to do is we're going to read some data from the ultrasonics. 01:32.980 --> 01:38.370 And so, Avery, let's say every 100 millisecond I saw in the loop. 01:39.160 --> 01:41.980 So what we could do is do the action. 01:42.260 --> 01:45.220 OK, and then delay 100. 01:45.820 --> 01:49.550 But I'm not going to use delay here for obvious reasons. 01:49.820 --> 01:52.760 Let's start the project with clean code. 01:52.960 --> 01:57.820 So what I'm going to do is create two variables here and signed long. 01:59.150 --> 02:01.070 That's the last time. 02:04.100 --> 02:04.670 So, Nick. 02:05.660 --> 02:06.220 Trigger. 02:06.290 --> 02:09.350 So last time we had to use the trigger on the ultrasonic sensor. 02:11.440 --> 02:15.150 And unsigned, long, ultra. 02:16.090 --> 02:16.640 So, Nick. 02:17.560 --> 02:25.210 Trigger delay, which is one hundred milliseconds, so if you remember from the last listen, we are 02:25.210 --> 02:27.630 going to do two things to get the distance. 02:27.640 --> 02:32.890 First, to trigger a trustfulness insult and then to read the data. 02:33.400 --> 02:38.870 So if we want to measure a distance every 100 milliseconds, we have to trigger the an extent. 02:39.060 --> 02:40.960 So every 100 milliseconds. 02:41.110 --> 02:43.930 So now what I'm going to do here is if. 02:45.100 --> 02:53.350 Time now, so if I want to use time now, let's do unsigned, long time now, please release. 02:54.480 --> 02:57.210 OK, minus the last time. 02:58.740 --> 03:04.600 This is the duration since the last time, if the duration is greater than the delay. 03:06.240 --> 03:15.540 What we do is we do last time and we add the delay, so I'm going quite fast here because that's something 03:15.540 --> 03:21.130 that we have seen in the time functionality section and we have also seen that multiple times since. 03:21.450 --> 03:27.840 So if it's not clear for you, please go back to the time section to practice more on this functionality 03:28.050 --> 03:30.730 and then here I can do the action. 03:31.320 --> 03:31.710 All right. 03:32.610 --> 03:38.740 There you can see once you know how to use this with the time functionality we've missed, it's really 03:38.760 --> 03:39.690 not that complicated. 03:39.690 --> 03:42.810 And you can create the set up for your project in no time. 03:43.140 --> 03:53.710 So now the action is what the action is, trigger sensor and then read the pulse on equal footing that 03:53.730 --> 03:54.990 we have two actions. 03:55.600 --> 04:01.710 What I'm going to do is to separate those two and I'm going to create a function first void. 04:02.680 --> 04:06.490 Trigger will try to sneak and some. 04:07.590 --> 04:13.860 They create a new function just so we can trigger the sensor so voided because, well, we don't need 04:13.860 --> 04:20.010 to return anything and no parameter because we have everything we need right here, we don't need to 04:20.010 --> 04:21.070 add any other parameter. 04:21.600 --> 04:29.160 So in this function, we are going to put the trigger pin too high for 10 microseconds. 04:29.460 --> 04:32.970 So we make sure that we have the PIN code trigger pin outputs. 04:33.000 --> 04:35.730 Yes, because if we do have these, then that will not work. 04:36.300 --> 04:38.310 So what I'm going to do first digital. 04:38.610 --> 04:39.240 Right? 04:40.690 --> 04:42.010 Trigger happy. 04:42.580 --> 04:48.700 Actually, I'm going to set it to low and then use Lake microseconds. 04:49.810 --> 04:52.750 We have two microseconds, why is that? 04:52.760 --> 04:56.650 Because because to trigger the sensor, you need to send a pulse. 04:56.720 --> 05:03.670 So you need to send a clear signal that goes from low to high or 10 microseconds and then to low again. 05:04.070 --> 05:10.700 The thing is that when you enter this function, you don't necessarily know what was the previous state 05:10.700 --> 05:11.360 for the trigger. 05:11.570 --> 05:14.730 So if it was already high, then that's not going to work. 05:14.960 --> 05:21.190 So we first set it too low for two microseconds, OK, just in case the signal was already high. 05:21.500 --> 05:26.150 So we can have a clear puts or the trigger and then digital. 05:26.270 --> 05:26.780 Right. 05:28.000 --> 05:32.110 Trigger in high and then we wait. 05:33.220 --> 05:34.810 Michael Tegan's. 05:36.040 --> 05:43.750 With then that's what we need, that's the minimum duration we need, and then, of course, don't forget 05:43.750 --> 05:45.280 digital rights. 05:46.490 --> 05:49.250 Trigger in law. 05:50.660 --> 05:57.890 So this would create a signal that goes low and then high for 10 microseconds and then low again, and 05:57.890 --> 06:00.420 this is the trigger for the ultrasonic sensor. 06:01.040 --> 06:04.640 So here we are going to do trigger. 06:05.940 --> 06:07.440 Ultra sonic. 06:09.320 --> 06:16.610 I'm going to call the function, so now that we have triggered the Senso, well, we need to read the 06:16.610 --> 06:24.380 A.P. to actually get the data from the DICENZO and then to convert this data into a reasonable distance 06:24.380 --> 06:26.040 that we human can reach. 06:26.300 --> 06:34.400 And I'm going to create a new function double get the truck, Sonique and distance. 06:36.220 --> 06:37.390 OK, why double? 06:37.400 --> 06:44.960 Because we are going to compute the distance in centimeters and we are going to compute actually a float 06:44.960 --> 06:46.100 or a double number. 06:46.400 --> 06:48.060 So a number with a comma. 06:48.290 --> 06:54.500 So if we have double at the end, I'm just putting a here so we don't forget we have the return with 06:54.500 --> 06:55.930 a double take. 06:56.430 --> 06:57.150 OK, void. 06:57.180 --> 06:59.450 You don't have any return but double you have a return. 06:59.810 --> 07:02.640 And now what are we going to do in this function? 07:03.080 --> 07:11.940 Well, the first thing we need to do is to get the data from the senso using the pulse in function. 07:11.960 --> 07:20.390 So it should arrange OK, so first and then uppercase I OK, both in and what are the parameters we 07:20.390 --> 07:21.090 need to give. 07:21.290 --> 07:22.880 We need to give two parameters. 07:23.030 --> 07:25.400 First, the ping equal. 07:28.740 --> 07:35.460 So that's the pain we have defined here, and that's also a pain that we have set as inputs very important, 07:36.240 --> 07:38.310 the Philippines and then the mode. 07:39.270 --> 07:46.590 I'm going to the high, so if you remember, we can have Moad High on Moad look here because the signal 07:46.590 --> 07:49.880 is low by default and then the pulse is high. 07:50.370 --> 07:51.900 Then we put the most high. 07:52.080 --> 07:54.670 If it's the opposite, you put the low. 07:54.720 --> 07:57.640 But this depends on the sensor is that we don't have a choice. 07:57.750 --> 07:59.640 That is how the sensor works. 08:00.150 --> 08:00.840 Semicolon. 08:00.840 --> 08:02.380 And of course, I'm going to say this. 08:02.390 --> 08:06.770 So the pulsing will return and unsigned long. 08:06.780 --> 08:08.100 So that's duration. 08:10.120 --> 08:14.290 It will return duration in microseconds. 08:14.320 --> 08:18.130 OK, so you will get the duration in microseconds of the post. 08:18.580 --> 08:23.600 The thing is, I'm going directly to cast it as double that. 08:23.620 --> 08:31.410 What this will do is it will read this as an unsigned long and then because the tape here is double, 08:31.420 --> 08:34.210 it would cost unsigned long as a double. 08:34.390 --> 08:38.990 And we need this because then we are going to perform operations with double. 08:39.040 --> 08:44.130 OK, so that's better to perform an operation between doubles when you already have a double time. 08:45.050 --> 08:50.360 But we get the duration in microcircuitry that puts duration micros. 08:50.390 --> 08:58.280 So this is clearer and then we are going to measure so double distance we are going to measure the distance 08:58.490 --> 09:03.640 from the duration and how to measure the distance, what unfolds, going to give you the easy formula 09:04.310 --> 09:05.480 and then the explanation. 09:06.080 --> 09:12.310 If you want the distance in centimeters, you're going to do duration divided by fifty eight. 09:12.710 --> 09:15.420 And don't forget fifty eight point zero. 09:15.690 --> 09:18.190 OK, so this is a double. 09:18.260 --> 09:19.590 This is a double. 09:19.610 --> 09:26.870 So the result will be a double if you use unsigned, long integer or similar data type. 09:27.140 --> 09:32.660 The thing is that the computation during the computation, some numbers will be truncated. 09:33.020 --> 09:36.520 OK, so you may not have a very precise result here. 09:36.530 --> 09:38.870 We use doubles, so we use a number. 09:38.870 --> 09:45.290 We come every time, which means that we would get a precise computation and then return. 09:46.670 --> 09:47.300 Dist.. 09:48.450 --> 09:49.610 All right, can remove this. 09:50.440 --> 10:00.090 OK, so this is four centimeter, if you want to get the distance in inches, you have to divide by 10:00.090 --> 10:02.280 one hundred and forty eight. 10:03.460 --> 10:11.980 You can just divide by 58, get the distance in centimeter and then convert centimeters, two inches, 10:12.000 --> 10:13.760 so four inches. 10:14.260 --> 10:16.470 So how do we get this 58? 10:17.200 --> 10:18.420 Because that value will work. 10:18.430 --> 10:25.480 But it's also nice if we understand why it's 58 and I'm not going to give you the complete mathematical 10:25.690 --> 10:33.190 computation to get to that number and that number simply just a quick few points that maybe will help 10:33.190 --> 10:35.170 you to understand where it comes from. 10:35.530 --> 10:45.280 So basically to measure the distance, you need to multiply the duration of the signal with the speed 10:45.280 --> 10:46.370 of the velocity. 10:46.600 --> 10:51.100 And this is the speed of velocity of the sound in the air. 10:51.130 --> 10:53.970 OK, because this is an interesting sensor. 10:53.980 --> 10:58.730 It will send an ultrasound on each wave, which can be considered also as a sound. 10:59.260 --> 11:07.330 So this is the speed of the sound in the approximately three hundred and forty meters per second. 11:07.900 --> 11:14.120 Key thing is that the duration here is in microseconds and the distance you want is in centimeters. 11:14.440 --> 11:26.290 So if you translate meter the signal in centimeter per microsecond, then you get zero point zero thirty 11:26.290 --> 11:26.590 four. 11:27.250 --> 11:32.350 I'm not going to explain in detail how to go from there, but basically what you have to do then is 11:32.350 --> 11:36.870 to do duration times zero point zero thirty four. 11:37.360 --> 11:44.740 And this is actually the total duration for the wave from the senseor to the object and the object to 11:44.740 --> 11:47.830 the because the wave will bounce back and come back. 11:48.280 --> 11:55.840 So you need to divide the result by two to only get the duration of the wave from the sensor to the 11:55.840 --> 11:58.210 object, all just from the object to the sensor. 11:58.220 --> 11:59.310 OK, the same thing. 11:59.650 --> 12:00.970 And when you do this. 12:01.960 --> 12:03.310 OK, when you. 12:04.520 --> 12:10.610 Multiply by this number, this is the same you can see the contradiction, this is the same as dividing 12:10.610 --> 12:14.230 by about 58 or centimeters. 12:14.420 --> 12:18.440 And if you want to convert in inches by dividing by one hundred forty eight. 12:18.590 --> 12:18.890 All right. 12:18.890 --> 12:21.110 So I'm not going to go too deep on this. 12:21.440 --> 12:28.340 If you don't understand everything, that's quite OK, because practically just need to know you need 12:28.340 --> 12:31.670 to divide it by 58 or divide by 140. 12:32.210 --> 12:40.410 So in that get ultrasonic distance function, we first get the duration in micro of the pulse in function. 12:40.850 --> 12:45.000 We divide by 58 and this gives us the distance in centimeters. 12:45.350 --> 12:51.730 So then what we can do here is we can do tail that rings. 12:51.740 --> 12:55.940 Ellen, get ultra sonic. 12:57.770 --> 12:58.280 Dist.. 12:59.360 --> 13:07.160 So we first trigger the senso and then we call to get ultrasonic distance function we triggers, and 13:07.160 --> 13:12.200 so we read the data from the sensor and we compute the distance. 13:12.200 --> 13:14.090 And because here we are right on a double. 13:14.130 --> 13:16.330 We just printed in the sale. 13:16.340 --> 13:17.320 We say the print. 13:17.870 --> 13:22.610 OK, note that maybe you have seen this and this seems weird to you. 13:22.620 --> 13:25.400 Why do we use daily microseconds in our code? 13:25.670 --> 13:29.130 Because I just said before that you should not use Gelee in your code. 13:29.420 --> 13:32.560 Well, the thing is that there are actually two exceptions to that. 13:32.570 --> 13:38.240 If Charamba one is to use the in the setup function because this is just the setup function that is 13:38.240 --> 13:39.800 going to be executed once. 13:39.980 --> 13:42.710 So if you need to wait two or three seconds here, that's OK. 13:42.720 --> 13:45.860 That's just going to happen once and then that's it. 13:46.280 --> 13:52.670 And in the loop function because this would happen in the function you can use if you need to, a small 13:52.670 --> 13:54.590 amount of delay microseconds. 13:54.680 --> 13:56.570 OK, here it's two and 10. 13:56.590 --> 14:00.080 So that would be 12 microseconds that you spend here at least. 14:00.290 --> 14:01.400 Now, this is very short. 14:01.430 --> 14:06.470 So this will block the program, of course, but for a very, very, very short amount of time, which 14:06.470 --> 14:07.310 is not a problem. 14:07.440 --> 14:13.520 OK, and here anyway, you need to wait 10 microseconds between those two instructions so you could 14:13.520 --> 14:18.330 do it in a different way, but that would complicate the code a lot. 14:18.740 --> 14:25.940 So here basically you are going to wait for 12 microseconds every 100 millisecond. 14:26.510 --> 14:33.530 OK, so the ratio, if we compute the ratio, you are going to wait 12 microseconds every one hundred 14:33.530 --> 14:40.940 milliseconds, which is I'm going to add three zeros, which is 100000 microseconds. 14:41.310 --> 14:45.010 I'm going to multiply that by 100 to get a percentage. 14:45.440 --> 14:53.270 You are going to wait for zero point zero 12 percent of the time, which is really, really not that 14:53.270 --> 14:53.690 much. 14:56.170 --> 15:00.820 So in this case, you can see using de microsurgeons will not be a problem for program. 15:01.450 --> 15:01.890 All right. 15:02.380 --> 15:05.020 So the code seems to be good. 15:05.560 --> 15:08.660 And now let's applaud the program here. 15:09.400 --> 15:11.710 Let's limit the truck. 15:12.900 --> 15:13.260 Nick. 15:15.910 --> 15:17.180 OK, we have an error. 15:17.440 --> 15:22.600 Duration was not declared in this scope, yes, because, of course, if I don't use the same variable 15:22.600 --> 15:24.180 name, that's not going to work. 15:24.970 --> 15:25.930 Let's upload. 15:28.700 --> 15:34.670 So it's done compiling and uploading, done uploading, and now I'm going to happen to say Moniteau. 15:35.780 --> 15:36.240 Right. 15:36.260 --> 15:43.280 So we have some values here, and you can see I have one hundred and forty centimeters, as you can 15:43.280 --> 15:48.810 see there is nothing in front of the SENSEOR but actually on this side, OK. 15:48.830 --> 15:55.130 So in front of the center, on this side of the room, there is a wall in the room, my arm and the 15:55.130 --> 15:58.850 wall is actually at one hundred and forty centimeters. 15:58.850 --> 16:00.110 So that's why you have this video. 16:00.500 --> 16:07.610 If the wall was not here, I would read maybe the maximum value, which is 400 centimetre or four meters. 16:07.910 --> 16:10.870 So if you have nothing, you will reach the maximum value. 16:10.910 --> 16:17.120 OK, now I'm going to put my hand here in front of the stencil and you can see I have No. 16:17.390 --> 16:21.900 Eight, about eight centimetre between eight and nine. 16:22.190 --> 16:28.460 I'm going to go closer and you can see that five six is closer. 16:28.610 --> 16:35.660 We get five and you can see the closer I get, we start to get some weird values. 16:35.960 --> 16:43.970 OK, but actually you can see that the two centimeter minimum that is advertised by DICENZO is not ready 16:43.970 --> 16:46.550 to centimeter in mage's. 16:47.000 --> 16:53.290 Well, the president I can get to six or five centimeters, not not less than six or five. 16:53.300 --> 16:54.770 So that is the practical value. 16:54.800 --> 17:01.190 OK, you should always measure the practical value compared to the theoretical one that is usually different. 17:01.610 --> 17:07.950 And as you can see, this is Korecki walking when I put an obstacle in front of the stencil. 17:07.970 --> 17:10.700 Well, you can see the value decreases. 17:10.700 --> 17:12.650 We have the great value in centimeters. 17:13.070 --> 17:16.010 If you want, you can measure exactly with the rule. 17:16.010 --> 17:21.620 You can you can measure the distance you get and you can see if the result is correct. 17:22.430 --> 17:22.820 All right. 17:22.830 --> 17:31.640 So now you can measure a distance from your Arduino secretes and an object on a wall that is in the 17:31.640 --> 17:35.840 under unmount of the Adreno using the ultrasonic sensor.