1 00:00:07,090 --> 00:00:12,190 ‫Welcome to the temperature sensor interface explain the lecture in this lecture I'm going to explain 2 00:00:12,220 --> 00:00:19,060 ‫how various temperature sensors work as well as how to interface your FPGA Elmore to a temperature sensor 3 00:00:20,230 --> 00:00:22,030 ‫various temperature sensors. 4 00:00:22,030 --> 00:00:26,750 ‫There are multiple different ways you can sense temperature and digital system. 5 00:00:26,770 --> 00:00:30,780 ‫There are three common components or sensors that are used. 6 00:00:30,790 --> 00:00:37,480 ‫We have a thermistor thermocouples or temperature I see is when the temperature I see or integrated 7 00:00:37,480 --> 00:00:44,450 ‫circuits either have a digital interface or an analog interface. 8 00:00:44,580 --> 00:00:51,270 ‫Let's talk a little bit about the sensor operation or a thermistor is a temperature changing resistor 9 00:00:51,570 --> 00:00:59,640 ‫as the temperature goes up or down the resistance of that thermistor changes and a thermocouple is kind 10 00:00:59,640 --> 00:01:00,750 ‫of a similar way. 11 00:01:00,750 --> 00:01:08,430 ‫However you have various types of thermal couples but you have a K type and type and type and based 12 00:01:08,430 --> 00:01:11,930 ‫upon the application you're using or the temperature you want to use. 13 00:01:12,030 --> 00:01:17,490 ‫You'll use that different type of thermocouple and the way they work is you have two dissimilar metals 14 00:01:17,850 --> 00:01:23,220 ‫that are fused together and as the temperature changes the voltage change between these two dissimilar 15 00:01:23,220 --> 00:01:24,460 ‫metals changes. 16 00:01:24,480 --> 00:01:29,760 ‫And so that's how you can kind of dictate the temperature when using a thermocouple and temperature 17 00:01:29,760 --> 00:01:32,690 ‫I see are very similar to a thermistor. 18 00:01:32,700 --> 00:01:39,750 ‫However you typically have an integrated circuit with a thermistor inside but it takes the output and 19 00:01:39,900 --> 00:01:46,890 ‫linear linearly relates to the temperature and you either have a digital interface or a straight analog 20 00:01:46,920 --> 00:01:47,750 ‫interface. 21 00:01:47,930 --> 00:01:52,430 ‫To that I see so little without the thermistors. 22 00:01:52,490 --> 00:01:58,000 ‫These are typically placed on PCBs to indicate if the board is getting too high. 23 00:01:58,220 --> 00:02:02,960 ‫If you have a processor a diode or something that's getting a lot of power to it and you want to make 24 00:02:02,960 --> 00:02:06,400 ‫sure it doesn't overheat you'll put it there Mr. on the PC keyboard. 25 00:02:06,440 --> 00:02:09,280 ‫Really close to indicate the temperature. 26 00:02:09,560 --> 00:02:14,130 ‫And the thing about the mystery is that a very accurate OBRA set temperature range. 27 00:02:14,300 --> 00:02:18,090 ‫If you have a very large range of their masters maybe not your best option. 28 00:02:18,320 --> 00:02:24,140 ‫But if you have a small range of temperatures and you want to know very accurately what that temperature 29 00:02:24,140 --> 00:02:26,780 ‫is what the mystery is the way to go. 30 00:02:26,990 --> 00:02:30,120 ‫And thermistors are there are non-linear. 31 00:02:30,140 --> 00:02:37,120 ‫So if you look they have like a curve that relates the temperature to the actual resistance value. 32 00:02:37,310 --> 00:02:40,040 ‫And so when you're calculating as you have to account for that curve. 33 00:02:40,370 --> 00:02:41,840 ‫But it makes a lot more accurate. 34 00:02:41,870 --> 00:02:47,840 ‫It's just a little bit more complex to interface with a fellow couple is. 35 00:02:47,890 --> 00:02:52,810 ‫These are typically used when you want to measure something that is extremely hot or really cold up 36 00:02:52,810 --> 00:02:53,470 ‫there mister. 37 00:02:53,500 --> 00:02:57,040 ‫For example if you have something that's you know hundreds of degrees here or there and hyster might 38 00:02:57,040 --> 00:02:58,860 ‫burn up and you can't use that. 39 00:02:59,020 --> 00:03:00,510 ‫So you use a thermocouple. 40 00:03:00,590 --> 00:03:05,860 ‫These I mean depending upon the type of thermocouple you are using to look in a datasheet but you can 41 00:03:05,860 --> 00:03:11,290 ‫have extremely hot or extremely cold temperatures and it worked really well for that. 42 00:03:11,290 --> 00:03:14,330 ‫And that typically would come on extremely long wires. 43 00:03:14,350 --> 00:03:19,150 ‫So you can have your measuring the temperature of something that's all the way across the room. 44 00:03:19,210 --> 00:03:23,040 ‫You don't have to worry about it you can sense it here on your board that's hundreds of feet away. 45 00:03:23,230 --> 00:03:27,610 ‫And so that's typically what you'll use them for a lot of like testing scenarios. 46 00:03:28,790 --> 00:03:30,700 ‫That we have a temperature I see. 47 00:03:30,840 --> 00:03:37,310 ‫These are placed on a PCB board similar to thermistor except that they have a linear output. 48 00:03:37,320 --> 00:03:42,900 ‫Now they're not as accurate as a thermistor but they're a lot easier to interface with because you can 49 00:03:42,900 --> 00:03:50,490 ‫apply a linear equation to tell you given what the output I see as I can directly relate that to a temperature 50 00:03:50,910 --> 00:03:53,580 ‫and that is what we're going to be using in our lab as a temperature. 51 00:03:53,580 --> 00:03:56,010 ‫I see. 52 00:03:56,140 --> 00:03:59,580 ‫So how do you interface your FPGA with the temperature I see. 53 00:03:59,770 --> 00:04:04,750 ‫Well there's two different options as we discussed before you can have a digital interface which is 54 00:04:04,750 --> 00:04:11,080 ‫really nice because then you can directly take your FPGA and interface with it whether it's using an 55 00:04:11,080 --> 00:04:16,860 ‫ice squared see GWM or a spy you or or any other type of interface. 56 00:04:16,850 --> 00:04:22,290 ‫You just have to look at the data sheet and it's going to tell you exactly how to read the actual temperature 57 00:04:22,300 --> 00:04:25,920 ‫that you or you can have an analog interface. 58 00:04:25,940 --> 00:04:33,240 ‫This is where the eyes see who output an analog voltage that directly relates to the actual temperature. 59 00:04:33,340 --> 00:04:37,110 ‫And if you go with an analog interface you have to have one or two things. 60 00:04:37,270 --> 00:04:44,260 ‫PJ may have an internal A to D converter and if you do then you can directly take the analog signal 61 00:04:44,650 --> 00:04:46,790 ‫and connected directly into the FPGA. 62 00:04:46,810 --> 00:04:51,830 ‫How ever if you don't have that you have to use an external ADC. 63 00:04:51,910 --> 00:04:54,990 ‫And so that's where depending upon the development board you're using. 64 00:04:55,180 --> 00:05:02,570 ‫You may have an external analog to digital converter or you may have an internal Now you understand 65 00:05:02,570 --> 00:05:06,740 ‫how a temperature sensor operates in ways you can interface with them with an FPGA. 66 00:05:06,740 --> 00:05:08,260 ‫Let's get started on the labs.