0 1 00:00:21,330 --> 00:00:22,040 Hello. 1 2 00:00:22,110 --> 00:00:27,930 In this video we are going to learn encoder basics for understand encoders. 2 3 00:00:27,930 --> 00:00:33,120 We need to know perfectly how optocoupler works in here. 3 4 00:00:33,120 --> 00:00:39,910 You can see structure of how optocouplers are working in led in here. 4 5 00:00:39,960 --> 00:00:47,020 Led goes high and then after led goes high transistor goes high. 5 6 00:00:47,070 --> 00:00:50,310 And in here zero volt from here. 6 7 00:00:50,310 --> 00:00:59,970 From this point is clear and the five volt DC is cut and encoder connected to Motor shaft for the give 7 8 00:00:59,970 --> 00:01:09,750 the position of the shaft with resolution precision with the pulses and the meant by resolution is number 8 9 00:01:09,750 --> 00:01:14,730 of encoders that one cycle can measure in here. 9 10 00:01:14,820 --> 00:01:19,480 You can see sample of encoder standard resolutions. 10 11 00:01:19,560 --> 00:01:28,740 For example if the resolution is here four thousand two hundred so one cycle is to three hundred and 11 12 00:01:28,800 --> 00:01:36,000 sixty degree and 360 degree divide by four thousand two hundred. 12 13 00:01:36,060 --> 00:01:46,050 So that encoder can measure every zero point zero eight hundred fifty seven degrees and if we have a 13 14 00:01:46,980 --> 00:01:54,990 encoder with the four thousand two hundred resolution so it can measure each zero point zero eight five 14 15 00:01:55,020 --> 00:02:05,010 seven degrees and encoders divided into two according to detection technology and optical sensing encoders 15 16 00:02:05,230 --> 00:02:14,100 and magnetic sensing encoders and encoders divided into two according to group we can say to group and 16 17 00:02:15,210 --> 00:02:23,330 this group is created by output type incremental encoders and absolute encoders. 17 18 00:02:23,490 --> 00:02:28,490 And if we say absolute encoders can be classified as follows. 18 19 00:02:28,530 --> 00:02:35,880 So according to communication technology absolute encoders can be to group and parallel type and they're 19 20 00:02:35,880 --> 00:02:43,450 serious type and parallel type encoders parallel type absolute encoders divided into two types. 20 21 00:02:43,470 --> 00:02:49,320 A single turn and multi turn there are separate conductors for each output. 21 22 00:02:49,380 --> 00:02:58,380 For example eight conductors are used for a eight bit output, serial type absolute encoders divided into two 22 23 00:02:58,380 --> 00:03:02,040 types as single turn and multiturn also. 23 24 00:03:02,100 --> 00:03:09,030 In this communication technology the output that is made with different electronical protocols and two 24 25 00:03:09,120 --> 00:03:18,120 conductors are used for example serial synchronous interface SSI serial asynchronous 25 26 00:03:18,180 --> 00:03:26,190 interface and interbus and profibus and canbus etc. for the serial type absolute encoders 26 27 00:03:26,220 --> 00:03:33,930 Another important issue is the working of and working on signal voltage of encoders. Encoders are 27 28 00:03:33,930 --> 00:03:44,910 produced at two operating voltages TTL and HTL so TTL encoders are supplied that typical 24 volt DC 28 29 00:03:44,910 --> 00:03:56,200 voltage value between 5 volt +/-%10 and HTL encoders are supplied between 10 to 30vdc 29 30 00:03:56,210 --> 00:03:59,550 and given output signal. 30 31 00:03:59,550 --> 00:04:09,990 This is the difference between HTL and TTL and again during this election it should be taken into consideration 31 32 00:04:09,990 --> 00:04:17,250 whether the absolute encoders will output in gray code or binary code which code is going to give us 32 33 00:04:18,000 --> 00:04:20,410 from absolute encoders. 33 34 00:04:20,430 --> 00:04:22,600 That is another important point. 34 35 00:04:22,860 --> 00:04:31,320 Another important point is the operating voltage of encoders.Incremental encoders it generates the signal 35 36 00:04:31,320 --> 00:04:37,980 in the rate of resolution one round for example the incremental encoder with the resolution of three 36 37 00:04:37,980 --> 00:04:42,810 thousand six hundred sends 3600 pulses to drive. 37 38 00:04:42,810 --> 00:04:49,010 For example vfd in one round and the driver collects this pulse and converts them into position 38 39 00:04:49,010 --> 00:04:49,960 information. 39 40 00:04:50,100 --> 00:04:54,120 When the motor rotates rotates in both directions this pulse. 40 41 00:04:54,120 --> 00:04:55,500 This is really important point. 41 42 00:04:55,500 --> 00:05:02,760 Now this pulse will be produced and the incremental encoder sends three signals to the driver to distinguish 42 43 00:05:02,760 --> 00:05:06,420 the direction and detect 0 crossing point. 43 44 00:05:06,660 --> 00:05:17,370 Another important point for the encoders the figure below shows in here a and b and Z signal.The Z signal 44 45 00:05:17,430 --> 00:05:22,330 is 0 crossing signal and output just give an output. 45 46 00:05:22,350 --> 00:05:33,110 Only once in a turn after one turn is completed in here for example we can get just once the Z signal. 46 47 00:05:33,120 --> 00:05:38,810 Note that the A and B signals in the figure are 90 degree phase apart. 47 48 00:05:38,940 --> 00:05:48,170 In here you can see in here we have a 90 degree phase apart and these signals output differently in 48 49 00:05:48,170 --> 00:05:54,150 fast to differentiate two direction of rotation in the forward rotation of the motor. 49 50 00:05:54,220 --> 00:06:01,710 The A signal will output before B signal and another important point B signal will output before 50 51 00:06:01,710 --> 00:06:07,780 the A signal when the motor direction change and other really important point is here. 51 52 00:06:07,890 --> 00:06:14,660 Inverter or drive will provide direction information based on the priority of these signals. 52 53 00:06:14,670 --> 00:06:24,920 You can see schematic of the channels A and B and Z and according to Time the outputs are in here. 53 54 00:06:24,930 --> 00:06:26,800 You can see it in here . 54 55 00:06:27,000 --> 00:06:36,000 A ,When the motor goes forward before B just goes high 90 degree is here or motor goes in other direction 55 56 00:06:36,210 --> 00:06:39,670 so B becomes high before A 56 57 00:06:39,720 --> 00:06:43,510 So let's take a look to encoder 0 test. 57 58 00:06:43,510 --> 00:06:50,830 Another really important point in here although the zero signal seems unnecessary. 58 59 00:06:51,060 --> 00:06:58,560 After one turn is completed it is really important for the testing to encoder.The encoder needs to pulse 59 60 00:06:58,590 --> 00:07:01,560 at the rate of the resolution in one turn. 60 61 00:07:01,560 --> 00:07:12,150 For example the resolution of encoder seven thousand two hundred then it turns fifteen point five turns 61 62 00:07:12,300 --> 00:07:14,250 after these turns. 62 63 00:07:14,250 --> 00:07:21,930 We need to get seven thousand two hundred multiply fifteen point five and equals one hundred eleven 63 64 00:07:21,930 --> 00:07:26,310 thousand six hundred pulses from the motor from the encoder. 64 65 00:07:26,400 --> 00:07:34,550 And if we get this value from the encoder we can say our encoder is working for example after one resolution. 65 66 00:07:34,680 --> 00:07:43,130 We need to get for example three thousand six hundred pulses from drive but we are getting six 66 67 00:07:43,170 --> 00:07:47,880 Three thousand five hundred pulses inside of the drive we are monitoring it. 67 68 00:07:47,880 --> 00:07:49,100 Imagine like this. 68 69 00:07:49,140 --> 00:07:55,950 So that means the malfunction in the optical circuit in the encoder or magnetic noise is because of 69 70 00:07:55,950 --> 00:08:02,310 magnetic noise or connection is losing looseness on the cable that connects the encoder to try. 70 71 00:08:02,580 --> 00:08:09,780 So these are maybe the problems of our encoders and speed limitation of encoder is another 71 72 00:08:09,810 --> 00:08:11,040 really important point. 72 73 00:08:11,340 --> 00:08:18,480 When you are choosing your encoder there is a speed limitation inside of the encoders so you can find 73 74 00:08:18,480 --> 00:08:20,670 it with this formula. 74 75 00:08:20,670 --> 00:08:26,440 Maximum electrical speed of encoder equals maximum for frequency response. 75 76 00:08:26,520 --> 00:08:32,730 Divide by pulses per revolution multiply 60 seconds per minute. 76 77 00:08:32,910 --> 00:08:42,730 So imagine we know the RPM or maximum electrical speed is this is it our encoder is spinning five 77 78 00:08:42,730 --> 00:08:49,140 thousand RPM and its produces pulses at two hundred and fifty hertz. 78 79 00:08:49,140 --> 00:08:50,760 But how can we know this. 79 80 00:08:50,760 --> 00:08:52,010 How can we find this. 80 81 00:08:52,110 --> 00:09:01,920 For example if it is three PPR , PPR means pulse per revolution and encoder so fifty five thousand. 81 82 00:09:01,920 --> 00:09:09,570 This is our turning speed or electrical speed equals B so maximum frequency response we don't know 82 83 00:09:09,930 --> 00:09:13,590 divided by three because it's three PPR. 83 84 00:09:14,100 --> 00:09:16,230 Then multiply by 60. 84 85 00:09:16,440 --> 00:09:26,200 So in this calculation we can get these maximum frequency response or two hundred and fifty hertz. 85 86 00:09:26,400 --> 00:09:34,580 So according to our PPR pulse per revolution or maximum frequency response or maximum electrical speed. 86 87 00:09:34,620 --> 00:09:41,010 So what we know for the encoder but we need to find maximum electrical speed after you buy your encoder 87 88 00:09:41,520 --> 00:09:48,570 you need to know maximum frequency response and divide it by pulse per revolution and multiply it 88 89 00:09:48,870 --> 00:09:55,430 by 60 seconds per minute and you are going to get your maximum electrical speed. 89 90 00:09:55,950 --> 00:10:04,450 So for the encoders there is a disk and also led and also light source like this in here. 90 91 00:10:04,530 --> 00:10:13,020 We have a led and in here we have optical devices a and b and in here we have one axe to turning for the 91 92 00:10:13,020 --> 00:10:15,060 encoder and this is disc. 92 93 00:10:15,060 --> 00:10:17,760 So this is turning first. 93 94 00:10:17,760 --> 00:10:24,090 This is looking to a channel a is the outside B is inside channel. 94 95 00:10:24,090 --> 00:10:31,360 So because of this structure ,90 degree phase apart is existing. 95 96 00:10:31,610 --> 00:10:39,830 So when this led is looking first to a channel and after encoder is turning it is looking in here just 96 97 00:10:40,100 --> 00:10:49,100 for example right here it is detecting A optical devices and giving A pulse and 90 degrees later it 97 98 00:10:49,100 --> 00:10:55,360 is seeing or detecting suddenly B optical devices and giving B pulse. 98 99 00:10:55,490 --> 00:11:00,410 In here you can see it how it is continue. 99 100 00:11:00,550 --> 00:11:12,400 And after one turn it is the take it is giving a Z or Z pulses to us ,so we can understand the encoder 100 101 00:11:12,400 --> 00:11:14,400 structure with these images. 101 102 00:11:14,500 --> 00:11:21,730 Just focus these images than you are going to understand the logic under of encoders. 102 103 00:11:22,060 --> 00:11:26,650 So in here we will after each side. 103 104 00:11:26,680 --> 00:11:32,770 We are getting output pulses and the output pulses of the incremental encoders are produced in 104 105 00:11:33,040 --> 00:11:40,790 NPN and PNP and open collectors circuits as well as circuits such as push pull and NPN + PNP and 105 106 00:11:40,790 --> 00:11:41,950 the line driver. 106 107 00:11:41,980 --> 00:11:50,500 So the important thing is here the outputs of the open collector in these schematic cannot be directly 107 108 00:11:50,500 --> 00:11:55,270 connected to drive or vfd.these or any other devices. 108 109 00:11:55,270 --> 00:12:02,230 So you can see in here open collector structure circuit structure and the push pull circuit structure 109 110 00:12:02,500 --> 00:12:07,930 and the line driver circuit structure in these images. 110 111 00:12:07,930 --> 00:12:11,650 So Let's go to magnetic encoder. 111 112 00:12:11,710 --> 00:12:17,950 So although they are not preferred very much because of their low resolution we will briefly talk about 112 113 00:12:17,950 --> 00:12:19,240 their existence. 113 114 00:12:19,240 --> 00:12:26,650 What is happening inside of the main magnetic encoders magnetic encoder is the magnetic one of the optical 114 115 00:12:26,650 --> 00:12:34,510 incremental encoder so many NS permanent magnets Poles are listed on the magnetic disk in here you 115 116 00:12:34,510 --> 00:12:40,760 can see an N and S poles in here. 116 117 00:12:40,930 --> 00:12:48,640 And this is how a affect device in here and it is going to detect these poles and in here we have a magnetic 117 118 00:12:48,640 --> 00:12:49,490 rotor. 118 119 00:12:49,570 --> 00:12:58,020 So with the shaft this pulse rotates and the hall element generates attention because of this tension. 119 120 00:12:58,120 --> 00:13:04,660 When they pass in front of the hall element sensitive to the magnetic field so the voltage is raised 120 121 00:13:04,780 --> 00:13:12,850 in the electronic circuit of the magnetic encoder because of the tension generating tension the voltage 121 122 00:13:12,850 --> 00:13:19,540 is going to up or raised and it is given to the driver in the form of pulses. 122 123 00:13:19,630 --> 00:13:28,990 So it is giving a pulse because of the poles are detected by hall device and because of this detection 123 124 00:13:29,290 --> 00:13:37,440 it generated tension after this tension the voltage is raised and it became a pulse. 124 125 00:13:37,480 --> 00:13:44,530 So absolute encoders what is happening for the absolute encoders and absolute encoders gives 125 126 00:13:44,530 --> 00:13:46,890 the real position of the shaft. 126 127 00:13:46,900 --> 00:13:52,270 For example in here all this is our shaft. 127 128 00:13:52,300 --> 00:13:53,200 -- 128 129 00:13:53,750 --> 00:14:02,350 Let's divide it this connected to the shaft into nine parts like in here and line parts will be positions 129 130 00:14:02,410 --> 00:14:07,440 our positions and we will created four tracks in each position. 130 131 00:14:07,450 --> 00:14:16,270 So in here for example if the 1 1 0 1 signal is resolved received from the absolute encoder. 131 132 00:14:16,360 --> 00:14:17,170 Let's take a look. 132 133 00:14:17,170 --> 00:14:22,360 1 1 0 1 in here as binary code. 133 134 00:14:22,360 --> 00:14:30,820 So it will say Ah ! I am at sixth position so we will say our encoder position is 6. 134 135 00:14:31,030 --> 00:14:38,470 Then we can understand the absolute position of our motor or devices. 135 136 00:14:38,500 --> 00:14:46,870 So for being absolute encoder can be seen below and for this actually provide the resolution of the 136 137 00:14:47,140 --> 00:14:54,090 encoder when passing regions give the position information will be obtained according to our binary number. 137 138 00:14:54,130 --> 00:15:02,970 So for the absolute encoders according to binary code we can divide our motor positions to 9 or 138 139 00:15:03,090 --> 00:15:04,090 a little more. 139 140 00:15:04,090 --> 00:15:09,120 Or for example 5 position we can create it like this. 140 141 00:15:09,250 --> 00:15:19,840 We can get absolute encoder gives a really real position of the shaft to us in here also you can 141 142 00:15:19,840 --> 00:15:29,650 see for example information 1 1 0 1 on the encoder output indicates that this rotor is in fifth position 142 143 00:15:29,980 --> 00:15:32,800 1 1 0 1. 143 144 00:15:32,810 --> 00:15:45,710 Where can we see the blacks ones are 1 and 1 and 0 and 1 as decimal eleven so it gives to us to another 144 145 00:15:45,730 --> 00:15:47,290 example in here. 145 146 00:15:47,350 --> 00:15:52,180 Our motor is stopping or waiting at the fifth position. 146 147 00:15:52,180 --> 00:15:56,440 The biggest value that you can get into binary number code with the four bits. 147 148 00:15:56,470 --> 00:16:05,200 If you are working with the four bit is you can divide it maximum 16 position dividing the shaft into 148 149 00:16:05,200 --> 00:16:12,520 sixteen positions provides a precision of one turn is 360 degree. 149 150 00:16:12,520 --> 00:16:22,330 So if we divided equally to 16 part we will get twenty two four point five degree after each position. 150 151 00:16:22,330 --> 00:16:26,610 We are going to move twenty two point five degree. 151 152 00:16:26,620 --> 00:16:29,310 This is absolute and real position. 152 153 00:16:29,680 --> 00:16:38,440 So in table we can get angular sensitivities and the resolutions of absolute encoders as can be seen 153 154 00:16:38,800 --> 00:16:46,570 as sixteen with absolute encoders can measure zero point zero zero fifty five degree fastness in here 154 155 00:16:46,870 --> 00:16:58,780 we can see sixteen bit resolution in here so we can use this formula two exponential by sixteen so 155 156 00:16:58,810 --> 00:17:05,810 this value is goes to this value, sixty five thousand five hundred and thirty six . 156 157 00:17:05,830 --> 00:17:08,620 Remember this was equal, 157 158 00:17:08,800 --> 00:17:10,410 One word value. 158 159 00:17:10,750 --> 00:17:13,400 From the previous lessons or lectures. 159 160 00:17:13,480 --> 00:17:20,700 So if we divide by 300 than 60 degree divide 160 161 00:17:21,380 --> 00:17:28,500 divide this one sixty five thousand five hundred thirty six. 161 162 00:17:28,660 --> 00:17:31,460 So we will get this value. 162 163 00:17:31,630 --> 00:17:33,750 So what can we say. 163 164 00:17:33,820 --> 00:17:42,550 Sixteen bit absolute encoder can measure zero point zero zero 55 degree fastness an absolute encoders 164 165 00:17:42,550 --> 00:17:48,940 can be produced to output in binary code as well as in the gray code the 0 and 1 fields on the disks 165 166 00:17:49,030 --> 00:17:54,450 of the encoders that output in gray code are placed according to this code. 166 167 00:17:54,490 --> 00:17:56,720 So this is binary code. 167 168 00:17:56,740 --> 00:17:59,440 This is gray code structure. 168 169 00:17:59,440 --> 00:18:01,630 So the reason for the choosing. 169 170 00:18:01,670 --> 00:18:03,610 Another important point is here. 170 171 00:18:03,790 --> 00:18:11,600 The reason for choosing gray code is that the data communication is security better than binary code. 171 172 00:18:11,620 --> 00:18:22,420 This is really security or safe according to binary code for grey code this code looks at the change 172 173 00:18:22,420 --> 00:18:26,860 in transition from one bit to the next bit in the next bit. 173 174 00:18:26,860 --> 00:18:31,770 After a bit if there is a same number it's a grey code is zero. 174 175 00:18:31,780 --> 00:18:35,870 If there is a different number the grey code is one. 175 176 00:18:36,010 --> 00:18:43,720 Let us check out this fifty six as decimal as binary 1 1 1 0 0 0. 176 177 00:18:44,020 --> 00:18:52,990 So if we put it all together from under and upper side look now 0 and 0 , so similar 177 178 00:18:52,990 --> 00:18:57,800 So the grey code is 0 , 0 0 is similar. 178 179 00:18:57,910 --> 00:19:01,630 So Grey code is 0 .0 and 1 179 180 00:19:01,690 --> 00:19:11,660 So the grey code becomes 1 , 0 than 1 and1 so our output is 0 and 1 and 1 again. 180 181 00:19:11,680 --> 00:19:16,870 So this is the same number is grey code is 0 and 1 and 0. 181 182 00:19:16,900 --> 00:19:19,790 So our grey code becomes 1. 182 183 00:19:19,810 --> 00:19:28,690 So if we put it together we will get this value 1 0 0 0 1 0 0 0 as grey code. 183 184 00:19:28,750 --> 00:19:36,050 The production of absolute encoders requires very thin technology compared with the incremental encoders. 184 185 00:19:36,250 --> 00:19:42,870 And this caused absolute encoders to be more expensive than incremental encoders. 185 186 00:19:42,880 --> 00:19:49,810 This is really important point another really important point in case of power failure or if the driver 186 187 00:19:49,810 --> 00:19:56,170 fails during the application since the location information will be deleted from the drivers memory 187 188 00:19:56,200 --> 00:19:59,700 due to number of pulses sent by incremental encoders. 188 189 00:19:59,830 --> 00:20:08,320 The system must be brought to the zero point and the application must be started again in absolute encoders. 189 190 00:20:08,440 --> 00:20:15,390 When electricity comes the signal from the encoders will give the real location information and the 190 191 00:20:15,400 --> 00:20:19,750 application can be continued from where it left off. 191 192 00:20:19,750 --> 00:20:21,300 This is really important. 192 193 00:20:21,400 --> 00:20:27,390 Absolute encoders should be used if the system is able to continue operating from where it left off after 193 194 00:20:27,390 --> 00:20:32,980 the arrival of electricity or if reaches to zero point of electricity is arrives. 194 195 00:20:33,160 --> 00:20:39,730 And if the material remaining in the system increases to the point of passing to the zero point 195 196 00:20:40,180 --> 00:20:42,820 it will increase the cost. 196 197 00:20:42,820 --> 00:20:51,460 In fact there is another encoder that is the mixture of these two encoders but that gives absolute value. 197 198 00:20:51,460 --> 00:20:58,710 So this encoder operates incrementally but by counting battery pulses with a microprocessor install 198 199 00:20:58,710 --> 00:21:07,960 on it it performs the necessary calculations and sends absolute value to the drive in here also some 199 200 00:21:08,680 --> 00:21:18,130 very thin technology is produced by very thin technology encoders and incremental encoder. 200 201 00:21:18,130 --> 00:21:26,710 This in here an absolute grey code encoder structure is here so I'm finished for this video. 201 202 00:21:26,740 --> 00:21:28,230 See you in the next video.