1 00:00:01,680 --> 00:00:02,500 Hello everyone. 2 00:00:02,500 --> 00:00:06,910 Welcome to lab 7 R C servo. 3 00:00:07,270 --> 00:00:13,710 Here are some servo uses servos are used in robotics and automation. 4 00:00:13,830 --> 00:00:18,760 These And each joint on the server are servo or the robot. 5 00:00:18,810 --> 00:00:25,150 You can see it's got every joint has a servo and what it uses to control a robot to give it however 6 00:00:25,270 --> 00:00:26,730 may servo's it has. 7 00:00:26,760 --> 00:00:33,330 Example here this robot it's got six different servos which allows six different degrees of motion. 8 00:00:33,360 --> 00:00:40,700 And this here on the right is the remote control plane which is what we'll be using in our lab today 9 00:00:40,980 --> 00:00:47,460 as an actual RCA servo which is using remote control planes remote control cars and things of that nature 10 00:00:48,900 --> 00:00:50,370 to control servo. 11 00:00:50,370 --> 00:00:54,140 They use this technique called Pulse with modulation. 12 00:00:54,240 --> 00:01:01,920 If you look here on the screen you'll see we've got a signal and the signal that comes in it brings 13 00:01:01,920 --> 00:01:05,110 a has to come at a specific frequency. 14 00:01:05,310 --> 00:01:09,680 And then right here it is dictated at a 10 to 20 milliseconds. 15 00:01:09,750 --> 00:01:11,090 You have to. 16 00:01:11,250 --> 00:01:16,910 That gives you your period there or the frequency you need which is going to be specified in the servo 17 00:01:16,920 --> 00:01:18,240 data sheet you use. 18 00:01:18,420 --> 00:01:25,110 And so for each different pulse with modulation percent or for the amount of time that it's a logic 19 00:01:25,110 --> 00:01:29,200 high year service is going to go in a different direction. 20 00:01:29,370 --> 00:01:35,270 So this here is not applicable to ours but just kind of gives you an idea if you're high for one no 21 00:01:35,280 --> 00:01:36,690 second year. 22 00:01:36,710 --> 00:01:42,380 R C servo arm is going to be to the to the left at a minimum value. 23 00:01:42,480 --> 00:01:49,230 And if it's high for 1.5 milliseconds proxy server is going to be at the center value or if you're high 24 00:01:49,230 --> 00:01:56,760 for two milliseconds you're RNC service is going to be at the maximum value of the servo that the RC 25 00:01:56,760 --> 00:02:03,660 server that I'm using for this lab is from Radio Shack and here's a picture of the datasheet or just 26 00:02:03,660 --> 00:02:05,060 kind of walk through it here. 27 00:02:05,340 --> 00:02:13,470 It tells you that the voltage justification is between 4.8 and 6 volts which you're probably wondering 28 00:02:13,470 --> 00:02:18,090 the basis to board that I'm using to control it only it runs at 3.3 volts. 29 00:02:18,090 --> 00:02:25,410 So if I were to take and hook this servo directly up to my base to board it wouldn't work it wouldn't 30 00:02:25,410 --> 00:02:26,890 be able to. 31 00:02:27,120 --> 00:02:30,310 Three four point three volts would not be recognized by this. 32 00:02:30,300 --> 00:02:33,270 So we're going to have to create a circuit on here. 33 00:02:33,300 --> 00:02:40,770 Or designed to take our 3.3 volt signal and create it into a FEIBEL signal. 34 00:02:41,010 --> 00:02:48,570 And it also gives you the torque speed size and weight of your servo and they use single meaning that 35 00:02:49,200 --> 00:02:53,610 this circuit has a total range of less than 160 degrees. 36 00:02:54,120 --> 00:03:00,390 And then it tells you there you can you can see it tells us what we need to have a pulse with modulation 37 00:03:00,390 --> 00:03:09,750 signal that has a frequency of 50 hers and the angle of the RC servo is directly relative to the logic 38 00:03:09,750 --> 00:03:20,070 high up on the table there you can see it 0.6 milliseconds a degree of zero a logic high for 0.9 no 39 00:03:20,070 --> 00:03:24,030 seconds gives you a 30 degree angle and so on and so forth. 40 00:03:24,420 --> 00:03:35,160 And so I mean table up here which shows you the the difference the different duration of your logic 41 00:03:35,160 --> 00:03:39,300 horizon and compares that to the air gives you a hexadecimal value. 42 00:03:39,450 --> 00:03:46,230 So for the logic high for zero point six seconds since in our design we're going to be using an 8 8 43 00:03:46,260 --> 00:03:55,230 bits resolution so the hexadecimal value for that would be 0 8 and for 0.9 seconds the hexadecimal value 44 00:03:55,230 --> 00:03:57,600 for that would be zero of B. 45 00:03:57,810 --> 00:04:03,090 And this is to give you a reference on the basis to board when you're clicking on the buttons to change 46 00:04:03,090 --> 00:04:06,410 the resolution of your sort of a controller. 47 00:04:06,540 --> 00:04:12,480 You can see the duration of logic high and you can relate it to the datasheet to see that you're getting 48 00:04:12,480 --> 00:04:14,890 that actual specified angle 49 00:04:17,610 --> 00:04:30,870 here is a S R C servo diagram design and B R C servo BICI that a big box is dotted around the outside. 50 00:04:30,870 --> 00:04:37,770 That is the what we would call the top level VHDL file that is like your main project file you're going 51 00:04:37,770 --> 00:04:46,650 to have in your in your project here and inside that design we've got two other VHDL designs. 52 00:04:46,790 --> 00:04:53,100 We've got that Polsce with modulation that Peto you got VHDL component which is what you're going to 53 00:04:53,100 --> 00:04:56,190 have to create in order to make this lab work. 54 00:04:56,400 --> 00:05:04,680 And we've got the hecks to seven segment component here which you should have created in lab 4. 55 00:05:04,770 --> 00:05:09,610 So you can just pull that right and you shouldn't have to modify anything if you've got that working. 56 00:05:09,900 --> 00:05:17,220 You just have to map it to your date of resolute resolution and register we have said here and you're 57 00:05:17,220 --> 00:05:25,550 also going to have to create an add or subtract process and add or subtract process to count. 58 00:05:25,740 --> 00:05:33,690 Count your button presses and then take those values and put them into the 8 bit resolution register 59 00:05:34,110 --> 00:05:40,350 and you also have two switches to determine whether it's an add or subtract process and a select if 60 00:05:40,350 --> 00:05:42,330 it's enabled or not enabled. 61 00:05:42,660 --> 00:05:47,130 And then your three point three output coming out of Bass's to board is going to have to go through 62 00:05:47,130 --> 00:05:55,410 a circuit or a step that up to 5 volt output which then in turn will go on to your RCA servo to the 63 00:05:55,410 --> 00:05:55,980 output there. 64 00:05:55,980 --> 00:06:00,420 So this is definitely designed you can do a screen capture on and get a picture of when you want to 65 00:06:00,420 --> 00:06:07,770 use this to help you as you start architecting and putting everything together. 66 00:06:07,770 --> 00:06:14,850 And here is a three point three to five all level shifting circuit already provided for you if you have 67 00:06:14,850 --> 00:06:15,990 a different way of doing this. 68 00:06:15,990 --> 00:06:23,010 Maybe you have a specific I see that takes a 3.3 people and converts it up to five all single then you 69 00:06:23,000 --> 00:06:29,010 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 70 00:06:29,010 --> 00:06:30,370 don't have to do this either. 71 00:06:30,400 --> 00:06:36,750 So but if you don't if you're like me and you've got a FEIBEL servo controlling with the three point 72 00:06:36,750 --> 00:06:42,090 people signal Here's a simple circuit you can use to do that. 73 00:06:42,150 --> 00:06:46,620 I'm not going to go through the specifics of how this works that's a whole other course an electronic 74 00:06:46,620 --> 00:06:53,640 circuit design but basically you can see the three point 3PL you bring that in and connected to your 75 00:06:53,640 --> 00:07:02,760 one k ohm resistor and two or two and thirty nine or four transistor which then the collector on that 76 00:07:02,760 --> 00:07:08,850 is connected to the another one resistor which is connected to the base of a second two and thirty nine 77 00:07:09,060 --> 00:07:14,850 for transistor where both of their emitters are connected to ground and B. 78 00:07:14,890 --> 00:07:20,790 Now it's important to know that on your second transistor that the five ought out is coming out of you 79 00:07:20,790 --> 00:07:28,350 need to have 100 ohm 150 or somewhere in that range a lot smaller resistor because you want to make 80 00:07:28,350 --> 00:07:32,010 sure that you've got the current to supply the RC servo. 81 00:07:32,010 --> 00:07:39,210 If you have too high a value like if you put a 10K resistor in there your servos just kind of chatter 82 00:07:39,300 --> 00:07:42,390 and it'll it'll be pretty messy and you try to figure out what's going on. 83 00:07:42,390 --> 00:07:51,510 So make sure you look at these values closely and follow this circuit set up exactly. 84 00:07:51,540 --> 00:07:55,580 So here's the tasks for our RC servo lab. 85 00:07:55,650 --> 00:08:01,440 You're going to create a pulse with modulation design using model sim to help you debug which I'll be 86 00:08:01,440 --> 00:08:07,690 giving you a test bench if you download the lab 7 file folders that folder. 87 00:08:07,740 --> 00:08:13,560 You'll have a pulse pole small with modulation design. 88 00:08:13,560 --> 00:08:15,100 Sorry about that. 89 00:08:15,300 --> 00:08:20,880 I'll give you a testbench in there and a tool command line file to help automate that process. 90 00:08:20,880 --> 00:08:26,910 And then you're gonna have to create a project in IMC and implement all the different parts of the RC 91 00:08:26,910 --> 00:08:28,060 servo controller. 92 00:08:28,190 --> 00:08:34,710 Patricia you previously on the diagram there and then as an extra if you can see if you can modify the 93 00:08:34,710 --> 00:08:38,390 ECF file and have it control the brightness of an LCD 94 00:08:41,370 --> 00:08:45,260 some hints here to get you started start by. 95 00:08:45,260 --> 00:08:52,170 First off you want to start by creating your Holsworth with modulation design using a test pulse with 96 00:08:52,170 --> 00:08:55,790 modulation dot the file I give you. 97 00:08:56,340 --> 00:09:01,650 You're going to want to test this because if this doesn't work then when you go ahead and try and create 98 00:09:01,650 --> 00:09:06,130 your design you're going to have all kinds of problems like nothing's going to work for you and you're 99 00:09:06,930 --> 00:09:09,150 sitting there just spinning your wheels trying to hear what's going on. 100 00:09:09,150 --> 00:09:16,320 So make sure that this pulse with modulation designed you create once you measure that work you can 101 00:09:16,320 --> 00:09:17,330 verify that works. 102 00:09:17,340 --> 00:09:22,020 Everything else we want the other parts have created in different labs so it should just be kind of 103 00:09:22,020 --> 00:09:24,950 wire things together and getting it to go. 104 00:09:25,230 --> 00:09:30,570 And then another thing you can do is take all our stuff from the previous lab such as the counter and 105 00:09:30,570 --> 00:09:36,450 the Nexus 7 segment display and see if you can put those together to get it where when you push a button 106 00:09:36,480 --> 00:09:40,890 you can get the results to display on the 7:7 displays. 107 00:09:41,010 --> 00:09:46,260 And once you get those two parts done at that point it should be relatively easy for you just kind of 108 00:09:46,740 --> 00:09:52,330 wire the thing together and use the references I gave you in previous lectures to figure it all out. 109 00:09:54,430 --> 00:10:03,250 Here you see a file I give you the pin mappings are you've got your ADD right here you can see on the 110 00:10:03,250 --> 00:10:09,370 far left that switch if you have a high or low is going to dictate whether you're adding or subtracting 111 00:10:09,850 --> 00:10:16,390 values and then your switch on the far right enables your pulse with modulation output. 112 00:10:16,420 --> 00:10:22,840 So if you could give that a logic high your pulse modulation output will go to zero if you get a logic 113 00:10:22,840 --> 00:10:23,500 one. 114 00:10:23,530 --> 00:10:29,220 It'll output whatever value you have and resolution register and then you're sent out. 115 00:10:29,270 --> 00:10:32,170 There's going to be the 8 bit 116 00:10:35,260 --> 00:10:41,150 8 bits of resolution you have in the resolution or register those we map to the seven Sigma display. 117 00:10:41,200 --> 00:10:42,930 As you can see circuit here. 118 00:10:43,150 --> 00:10:48,460 And then you've got the two buttons there that start reset buttons. 119 00:10:48,640 --> 00:10:55,000 If you click on those as they're going to add different values such as ones or one or five when you 120 00:10:55,000 --> 00:11:01,600 click on those you're going to see here your values go up and down based upon whichever one you click 121 00:11:02,020 --> 00:11:08,260 and then the top up there you can see you've got the pulse with modulation output and that you're going 122 00:11:08,260 --> 00:11:15,310 to want to wire directly into your RC servo pulse with modulation input when you look at the datasheet 123 00:11:15,370 --> 00:11:20,350 on the RC servo it's going to tell you what you need to connect your voltage waiting to connect the 124 00:11:20,350 --> 00:11:28,810 ground and what you need to connect to the your control your modulator input and the outcomes of this 125 00:11:28,810 --> 00:11:29,410 lab. 126 00:11:29,780 --> 00:11:37,030 Or that you should be able to understand how multiple VHDL designs can be reused in multiple VHDL designs 127 00:11:37,040 --> 00:11:39,290 which this is very useful. 128 00:11:39,290 --> 00:11:44,410 You'll come to find out that as we create a library visit Zeins you'll be using an array using them 129 00:11:44,830 --> 00:11:51,370 all over the place so it's definitely useful to keep these and have them handy and you'll become more 130 00:11:51,370 --> 00:11:57,470 comfortable with using model sim as you design your pulse with modulation component. 131 00:11:57,690 --> 00:12:01,770 You're pretty much having to come from the ground up on mass so you're going to use model assumed to 132 00:12:01,780 --> 00:12:07,050 verify and make sure everything's happening just as as you'd like. 133 00:12:07,600 --> 00:12:13,180 And also you got to understand how to control an RC servo motor using external components which is where 134 00:12:13,180 --> 00:12:16,900 we're using the transistors resistors and things like that. 135 00:12:16,900 --> 00:12:24,430 Take a 3.3 volt signal and convert it up to 5 volts signal and you're learning how to create a pulse 136 00:12:24,490 --> 00:12:27,720 with modulation design implementation in VHDL. 137 00:12:27,730 --> 00:12:29,140 There are other ways you can do this. 138 00:12:29,140 --> 00:12:38,080 You can use a microcontroller or you can use your own transistors and just a 555 timer and a whole slew 139 00:12:38,080 --> 00:12:38,710 of different ways. 140 00:12:38,710 --> 00:12:40,560 But this is one of the ways we can do it. 141 00:12:40,600 --> 00:12:42,520 And we're going to learn how.