‫Welcome to the temperature sensor interface explain the lecture in this lecture I'm going to explain
‫how various temperature sensors work as well as how to interface your FPGA Elmore to a temperature sensor
‫various temperature sensors.
‫There are multiple different ways you can sense temperature and digital system.
‫There are three common components or sensors that are used.
‫We have a thermistor thermocouples or temperature I see is when the temperature I see or integrated
‫circuits either have a digital interface or an analog interface.
‫Let's talk a little bit about the sensor operation or a thermistor is a temperature changing resistor
‫as the temperature goes up or down the resistance of that thermistor changes and a thermocouple is kind
‫of a similar way.
‫However you have various types of thermal couples but you have a K type and type and type and based
‫upon the application you're using or the temperature you want to use.
‫You'll use that different type of thermocouple and the way they work is you have two dissimilar metals
‫that are fused together and as the temperature changes the voltage change between these two dissimilar
‫metals changes.
‫And so that's how you can kind of dictate the temperature when using a thermocouple and temperature
‫I see are very similar to a thermistor.
‫However you typically have an integrated circuit with a thermistor inside but it takes the output and
‫linear linearly relates to the temperature and you either have a digital interface or a straight analog
‫interface.
‫To that I see so little without the thermistors.
‫These are typically placed on PCBs to indicate if the board is getting too high.
‫If you have a processor a diode or something that's getting a lot of power to it and you want to make
‫sure it doesn't overheat you'll put it there Mr. on the PC keyboard.
‫Really close to indicate the temperature.
‫And the thing about the mystery is that a very accurate OBRA set temperature range.
‫If you have a very large range of their masters maybe not your best option.
‫But if you have a small range of temperatures and you want to know very accurately what that temperature
‫is what the mystery is the way to go.
‫And thermistors are there are non-linear.
‫So if you look they have like a curve that relates the temperature to the actual resistance value.
‫And so when you're calculating as you have to account for that curve.
‫But it makes a lot more accurate.
‫It's just a little bit more complex to interface with a fellow couple is.
‫These are typically used when you want to measure something that is extremely hot or really cold up
‫there mister.
‫For example if you have something that's you know hundreds of degrees here or there and hyster might
‫burn up and you can't use that.
‫So you use a thermocouple.
‫These I mean depending upon the type of thermocouple you are using to look in a datasheet but you can
‫have extremely hot or extremely cold temperatures and it worked really well for that.
‫And that typically would come on extremely long wires.
‫So you can have your measuring the temperature of something that's all the way across the room.
‫You don't have to worry about it you can sense it here on your board that's hundreds of feet away.
‫And so that's typically what you'll use them for a lot of like testing scenarios.
‫That we have a temperature I see.
‫These are placed on a PCB board similar to thermistor except that they have a linear output.
‫Now they're not as accurate as a thermistor but they're a lot easier to interface with because you can
‫apply a linear equation to tell you given what the output I see as I can directly relate that to a temperature
‫and that is what we're going to be using in our lab as a temperature.
‫I see.
‫So how do you interface your FPGA with the temperature I see.
‫Well there's two different options as we discussed before you can have a digital interface which is
‫really nice because then you can directly take your FPGA and interface with it whether it's using an
‫ice squared see GWM or a spy you or or any other type of interface.
‫You just have to look at the data sheet and it's going to tell you exactly how to read the actual temperature
‫that you or you can have an analog interface.
‫This is where the eyes see who output an analog voltage that directly relates to the actual temperature.
‫And if you go with an analog interface you have to have one or two things.
‫PJ may have an internal A to D converter and if you do then you can directly take the analog signal
‫and connected directly into the FPGA.
‫How ever if you don't have that you have to use an external ADC.
‫And so that's where depending upon the development board you're using.
‫You may have an external analog to digital converter or you may have an internal Now you understand
‫how a temperature sensor operates in ways you can interface with them with an FPGA.
‫Let's get started on the labs.