WEBVTT 00:01.680 --> 00:02.500 Hello everyone. 00:02.500 --> 00:06.910 Welcome to lab 7 R C servo. 00:07.270 --> 00:13.710 Here are some servo uses servos are used in robotics and automation. 00:13.830 --> 00:18.760 These And each joint on the server are servo or the robot. 00:18.810 --> 00:25.150 You can see it's got every joint has a servo and what it uses to control a robot to give it however 00:25.270 --> 00:26.730 may servo's it has. 00:26.760 --> 00:33.330 Example here this robot it's got six different servos which allows six different degrees of motion. 00:33.360 --> 00:40.700 And this here on the right is the remote control plane which is what we'll be using in our lab today 00:40.980 --> 00:47.460 as an actual RCA servo which is using remote control planes remote control cars and things of that nature 00:48.900 --> 00:50.370 to control servo. 00:50.370 --> 00:54.140 They use this technique called Pulse with modulation. 00:54.240 --> 01:01.920 If you look here on the screen you'll see we've got a signal and the signal that comes in it brings 01:01.920 --> 01:05.110 a has to come at a specific frequency. 01:05.310 --> 01:09.680 And then right here it is dictated at a 10 to 20 milliseconds. 01:09.750 --> 01:11.090 You have to. 01:11.250 --> 01:16.910 That gives you your period there or the frequency you need which is going to be specified in the servo 01:16.920 --> 01:18.240 data sheet you use. 01:18.420 --> 01:25.110 And so for each different pulse with modulation percent or for the amount of time that it's a logic 01:25.110 --> 01:29.200 high year service is going to go in a different direction. 01:29.370 --> 01:35.270 So this here is not applicable to ours but just kind of gives you an idea if you're high for one no 01:35.280 --> 01:36.690 second year. 01:36.710 --> 01:42.380 R C servo arm is going to be to the to the left at a minimum value. 01:42.480 --> 01:49.230 And if it's high for 1.5 milliseconds proxy server is going to be at the center value or if you're high 01:49.230 --> 01:56.760 for two milliseconds you're RNC service is going to be at the maximum value of the servo that the RC 01:56.760 --> 02:03.660 server that I'm using for this lab is from Radio Shack and here's a picture of the datasheet or just 02:03.660 --> 02:05.060 kind of walk through it here. 02:05.340 --> 02:13.470 It tells you that the voltage justification is between 4.8 and 6 volts which you're probably wondering 02:13.470 --> 02:18.090 the basis to board that I'm using to control it only it runs at 3.3 volts. 02:18.090 --> 02:25.410 So if I were to take and hook this servo directly up to my base to board it wouldn't work it wouldn't 02:25.410 --> 02:26.890 be able to. 02:27.120 --> 02:30.310 Three four point three volts would not be recognized by this. 02:30.300 --> 02:33.270 So we're going to have to create a circuit on here. 02:33.300 --> 02:40.770 Or designed to take our 3.3 volt signal and create it into a FEIBEL signal. 02:41.010 --> 02:48.570 And it also gives you the torque speed size and weight of your servo and they use single meaning that 02:49.200 --> 02:53.610 this circuit has a total range of less than 160 degrees. 02:54.120 --> 03:00.390 And then it tells you there you can you can see it tells us what we need to have a pulse with modulation 03:00.390 --> 03:09.750 signal that has a frequency of 50 hers and the angle of the RC servo is directly relative to the logic 03:09.750 --> 03:20.070 high up on the table there you can see it 0.6 milliseconds a degree of zero a logic high for 0.9 no 03:20.070 --> 03:24.030 seconds gives you a 30 degree angle and so on and so forth. 03:24.420 --> 03:35.160 And so I mean table up here which shows you the the difference the different duration of your logic 03:35.160 --> 03:39.300 horizon and compares that to the air gives you a hexadecimal value. 03:39.450 --> 03:46.230 So for the logic high for zero point six seconds since in our design we're going to be using an 8 8 03:46.260 --> 03:55.230 bits resolution so the hexadecimal value for that would be 0 8 and for 0.9 seconds the hexadecimal value 03:55.230 --> 03:57.600 for that would be zero of B. 03:57.810 --> 04:03.090 And this is to give you a reference on the basis to board when you're clicking on the buttons to change 04:03.090 --> 04:06.410 the resolution of your sort of a controller. 04:06.540 --> 04:12.480 You can see the duration of logic high and you can relate it to the datasheet to see that you're getting 04:12.480 --> 04:14.890 that actual specified angle 04:17.610 --> 04:30.870 here is a S R C servo diagram design and B R C servo BICI that a big box is dotted around the outside. 04:30.870 --> 04:37.770 That is the what we would call the top level VHDL file that is like your main project file you're going 04:37.770 --> 04:46.650 to have in your in your project here and inside that design we've got two other VHDL designs. 04:46.790 --> 04:53.100 We've got that Polsce with modulation that Peto you got VHDL component which is what you're going to 04:53.100 --> 04:56.190 have to create in order to make this lab work. 04:56.400 --> 05:04.680 And we've got the hecks to seven segment component here which you should have created in lab 4. 05:04.770 --> 05:09.610 So you can just pull that right and you shouldn't have to modify anything if you've got that working. 05:09.900 --> 05:17.220 You just have to map it to your date of resolute resolution and register we have said here and you're 05:17.220 --> 05:25.550 also going to have to create an add or subtract process and add or subtract process to count. 05:25.740 --> 05:33.690 Count your button presses and then take those values and put them into the 8 bit resolution register 05:34.110 --> 05:40.350 and you also have two switches to determine whether it's an add or subtract process and a select if 05:40.350 --> 05:42.330 it's enabled or not enabled. 05:42.660 --> 05:47.130 And then your three point three output coming out of Bass's to board is going to have to go through 05:47.130 --> 05:55.410 a circuit or a step that up to 5 volt output which then in turn will go on to your RCA servo to the 05:55.410 --> 05:55.980 output there. 05:55.980 --> 06:00.420 So this is definitely designed you can do a screen capture on and get a picture of when you want to 06:00.420 --> 06:07.770 use this to help you as you start architecting and putting everything together. 06:07.770 --> 06:14.850 And here is a three point three to five all level shifting circuit already provided for you if you have 06:14.850 --> 06:15.990 a different way of doing this. 06:15.990 --> 06:23.010 Maybe you have a specific I see that takes a 3.3 people and converts it up to five all single then you 06:23.000 --> 06:29.010 don't you don't need to use this or if you have an RC server that accepts the 3.3 bold input then you 06:29.010 --> 06:30.370 don't have to do this either. 06:30.400 --> 06:36.750 So but if you don't if you're like me and you've got a FEIBEL servo controlling with the three point 06:36.750 --> 06:42.090 people signal Here's a simple circuit you can use to do that. 06:42.150 --> 06:46.620 I'm not going to go through the specifics of how this works that's a whole other course an electronic 06:46.620 --> 06:53.640 circuit design but basically you can see the three point 3PL you bring that in and connected to your 06:53.640 --> 07:02.760 one k ohm resistor and two or two and thirty nine or four transistor which then the collector on that 07:02.760 --> 07:08.850 is connected to the another one resistor which is connected to the base of a second two and thirty nine 07:09.060 --> 07:14.850 for transistor where both of their emitters are connected to ground and B. 07:14.890 --> 07:20.790 Now it's important to know that on your second transistor that the five ought out is coming out of you 07:20.790 --> 07:28.350 need to have 100 ohm 150 or somewhere in that range a lot smaller resistor because you want to make 07:28.350 --> 07:32.010 sure that you've got the current to supply the RC servo. 07:32.010 --> 07:39.210 If you have too high a value like if you put a 10K resistor in there your servos just kind of chatter 07:39.300 --> 07:42.390 and it'll it'll be pretty messy and you try to figure out what's going on. 07:42.390 --> 07:51.510 So make sure you look at these values closely and follow this circuit set up exactly. 07:51.540 --> 07:55.580 So here's the tasks for our RC servo lab. 07:55.650 --> 08:01.440 You're going to create a pulse with modulation design using model sim to help you debug which I'll be 08:01.440 --> 08:07.690 giving you a test bench if you download the lab 7 file folders that folder. 08:07.740 --> 08:13.560 You'll have a pulse pole small with modulation design. 08:13.560 --> 08:15.100 Sorry about that. 08:15.300 --> 08:20.880 I'll give you a testbench in there and a tool command line file to help automate that process. 08:20.880 --> 08:26.910 And then you're gonna have to create a project in IMC and implement all the different parts of the RC 08:26.910 --> 08:28.060 servo controller. 08:28.190 --> 08:34.710 Patricia you previously on the diagram there and then as an extra if you can see if you can modify the 08:34.710 --> 08:38.390 ECF file and have it control the brightness of an LCD 08:41.370 --> 08:45.260 some hints here to get you started start by. 08:45.260 --> 08:52.170 First off you want to start by creating your Holsworth with modulation design using a test pulse with 08:52.170 --> 08:55.790 modulation dot the file I give you. 08:56.340 --> 09:01.650 You're going to want to test this because if this doesn't work then when you go ahead and try and create 09:01.650 --> 09:06.130 your design you're going to have all kinds of problems like nothing's going to work for you and you're 09:06.930 --> 09:09.150 sitting there just spinning your wheels trying to hear what's going on. 09:09.150 --> 09:16.320 So make sure that this pulse with modulation designed you create once you measure that work you can 09:16.320 --> 09:17.330 verify that works. 09:17.340 --> 09:22.020 Everything else we want the other parts have created in different labs so it should just be kind of 09:22.020 --> 09:24.950 wire things together and getting it to go. 09:25.230 --> 09:30.570 And then another thing you can do is take all our stuff from the previous lab such as the counter and 09:30.570 --> 09:36.450 the Nexus 7 segment display and see if you can put those together to get it where when you push a button 09:36.480 --> 09:40.890 you can get the results to display on the 7:7 displays. 09:41.010 --> 09:46.260 And once you get those two parts done at that point it should be relatively easy for you just kind of 09:46.740 --> 09:52.330 wire the thing together and use the references I gave you in previous lectures to figure it all out. 09:54.430 --> 10:03.250 Here you see a file I give you the pin mappings are you've got your ADD right here you can see on the 10:03.250 --> 10:09.370 far left that switch if you have a high or low is going to dictate whether you're adding or subtracting 10:09.850 --> 10:16.390 values and then your switch on the far right enables your pulse with modulation output. 10:16.420 --> 10:22.840 So if you could give that a logic high your pulse modulation output will go to zero if you get a logic 10:22.840 --> 10:23.500 one. 10:23.530 --> 10:29.220 It'll output whatever value you have and resolution register and then you're sent out. 10:29.270 --> 10:32.170 There's going to be the 8 bit 10:35.260 --> 10:41.150 8 bits of resolution you have in the resolution or register those we map to the seven Sigma display. 10:41.200 --> 10:42.930 As you can see circuit here. 10:43.150 --> 10:48.460 And then you've got the two buttons there that start reset buttons. 10:48.640 --> 10:55.000 If you click on those as they're going to add different values such as ones or one or five when you 10:55.000 --> 11:01.600 click on those you're going to see here your values go up and down based upon whichever one you click 11:02.020 --> 11:08.260 and then the top up there you can see you've got the pulse with modulation output and that you're going 11:08.260 --> 11:15.310 to want to wire directly into your RC servo pulse with modulation input when you look at the datasheet 11:15.370 --> 11:20.350 on the RC servo it's going to tell you what you need to connect your voltage waiting to connect the 11:20.350 --> 11:28.810 ground and what you need to connect to the your control your modulator input and the outcomes of this 11:28.810 --> 11:29.410 lab. 11:29.780 --> 11:37.030 Or that you should be able to understand how multiple VHDL designs can be reused in multiple VHDL designs 11:37.040 --> 11:39.290 which this is very useful. 11:39.290 --> 11:44.410 You'll come to find out that as we create a library visit Zeins you'll be using an array using them 11:44.830 --> 11:51.370 all over the place so it's definitely useful to keep these and have them handy and you'll become more 11:51.370 --> 11:57.470 comfortable with using model sim as you design your pulse with modulation component. 11:57.690 --> 12:01.770 You're pretty much having to come from the ground up on mass so you're going to use model assumed to 12:01.780 --> 12:07.050 verify and make sure everything's happening just as as you'd like. 12:07.600 --> 12:13.180 And also you got to understand how to control an RC servo motor using external components which is where 12:13.180 --> 12:16.900 we're using the transistors resistors and things like that. 12:16.900 --> 12:24.430 Take a 3.3 volt signal and convert it up to 5 volts signal and you're learning how to create a pulse 12:24.490 --> 12:27.720 with modulation design implementation in VHDL. 12:27.730 --> 12:29.140 There are other ways you can do this. 12:29.140 --> 12:38.080 You can use a microcontroller or you can use your own transistors and just a 555 timer and a whole slew 12:38.080 --> 12:38.710 of different ways. 12:38.710 --> 12:40.560 But this is one of the ways we can do it. 12:40.600 --> 12:42.520 And we're going to learn how.