Seebeck & Peltier Effect - How Thermocouples & Peltier Cells work?

this is a so-called peltier cell and this here is a thermocouple maybe you think these have nothing to do one with each other but actually these are kind of the same but used in opposite purposes these two components have something to do with the union between two types of metal alloy and a certain current flowing through these wires this process is based on the so-called thermoelectric effect it's quite incredible than when you have this union of two different metal alloys connected in a loop if you keep one very cold and the other end very hot there will be a current flow created inside of this loop and the backwards effect is that when you supply current to this loop of wire one end will get hot and the other one very cold of course we could use these two effects in everyday applications for example to measure temperature or to heat or to cool something that's what the thermocouple and the peltier cell are doing so today we have yet another theory episode so in this video i will show you the theory inside of these components why this thermoelectric effect occurs and what applications we have for these elements we will have the chemistry and the physics parts and some electrical fundamentals so make sure that you subscribe and activate the notification bell consider supporting me on patreon so guys let's get started [Music] this episode is sponsored by the pcb manufacturer company glc pcb their main services are the two layer pcbs for only two dollars also four and six layer pcbs the smt assembly process where you will get the pcbs with all the components already soldered in place and also the smt stencil for soldering smd components with solder paste the quality of the pcbs is amazing i use their services all the time and always get good results for only 2 dollars you have 5 pcbs of any color that you want so go to jlcpcb.com upload the gerber files of your design and order the pcbs in just a couple of minutes what's up my friends welcome back so remember that today i will explain the thermocouple and the peltier modules and for that we will have to know the so called seaback effect and also the peltier effect after that we will see what use we could give to these configurations so first thing first the thermocouple inside this very tiny ball of metal there are two different types of alloys joined together when i hit this up they will create a voltage drop as you can see here on my multimeter this voltage drop is extremely low in the range of 40 micro volts per each celsius degree but we can still use this all we have to do is to add an amplifier and amplify the voltage to something that we could easily read so we do that and then we can measure the temperature so that's exactly what this device is doing this is a k-type thermocouple and this device here has an amplifier and a correlation between the voltage read and the temperature and that's how we can measure that temperature but the interesting thing is not the amplifier part and the temperature reading but how just two simple wires merge together could create a voltage drop well let me cut this thermocouple wire inside we have actually two wires one is covered with some red stripes and the other one with some blue stripes these are not copper wires actually these are made of two different alloys one is called como and the other one alumo and that's what makes this process possible so look if i merge them in a loop and place my multimeter in series well there's nothing happening for now but now i heat up one side of the loop and there you go as you can see a current is now flowing through this loop of a few hundreds of milliamperes but how is this possible because there is no current source in this circuit so let's go deeper and understand the seebeck effect okay so imagine a wire made out of a metal so this is a conductor the fact that this material is a conductor that means that it has these free electrons which are able to move around under voltage potential difference but at the same time we also know that these electrons have a thermal energy actually that's what temperature is electrons bouncing around so at the temperature of absolute zero these electrons are not moving but the higher is the temperature they start vibrating more and more having more thermal energy so now imagine for example this wire is at 20 degrees celsius and all the electrons inside are vibrating with the same energy but now we hit one end of this wire so that means the electrons on the left side will jiggle a little bit more because they have more thermal energy so that will make the electrons to be in some sort of speaking more separated because now they vibrate more so on the left side we'll have less electrons because they are further away one from each other but on the other side the electrons are get pushed so we will have slightly more electrons on the right side so guys do you see what this is this simulates a voltage differential because we have a deficit of electrons on the left side and more electrons on the right side creating a certain positive potential on the left and the negative one on the right okay so this point here will be the principle of the seebeck effect so let's go even deeper at the same time it's quite obvious that different methods will have a different amount of free electrons and this will require different quantities of thermal energy to start vibrating more and more so that's why we use two types of metal alloys for our experiment so for example heating 1 to 100 degrees might create a certain voltage difference but then hitting the other one at the same temperature since the alloy is different the seebeck effect is not as pronounced so the voltage difference will be different so now we take these two wires and join them in a loop so remember that the top wire will create a voltage drop that let's say is greater than the voltage drop on the bottom wire and we show that with the bigger v plus and the v minus so once again obviously the current flow in the top wire is greater than the current flow in the bottom wire from left to right to understand this better let's give some values the top wire is pushing let's say 20 units of electrons clockwise and the bottom wire is pushing 10 units of electrons counterclockwise so now if i sum up these current values which are just electrons moving around the top current value will win because the value is higher so we would have 20 plus negative 10 which is equal to 10 units of electrons flowing clockwise so we will have a total net current value like this inside of the loop so that's it guys that's how we create that current on our wires when we present a temperature difference between the two ends of the loop with two different alloys so that was the seebeck effect the current value as you can see is very low around 300 microamps so we can't really use this with any device so that's why we have this thermocouple amplifier so we amplified a small voltage 100 times or so and now we could read this with a microcontroller for example so if you know the curve with the relation between the temperature and the voltage drop on the amplifier output we could easily use this device for temperature measurement actually that's exactly what we do with the k-type thermocouple like this one so that's how easy is to measure temperature using just two simple wires with the seebeck effect but then we have the reverse effect which is called peltier effect and i will explain that with the so called peltier cell with the seebeck effect we have seen that if you create a temperature difference between the two ends of these wires a voltage drop is created between the ends of the loop but what if you apply that voltage difference to this wire's loop well just the opposite will happen now a temperature difference will be created as you can see i apply a voltage to this peltier module and on one side will get very hot and the other side will get very cold one side will get so cold that it could even freeze water so it's below zero degrees to understand why this is happening we need to take a different approach and see this metal alloys differently remember from the diode theory video that electrons are orbiting the nuclei of the metal but these orbits are quantified so that means we have the orbit of n1 which is representing the lowest energy then n2 and 3n4 and so on till the maximum energy an electron could have for that specific molecule of metal so without any external energy the electrons in the metal will always try to occupy the less energy orbits closer to the nuclei of the ion the more electrons we put in they will keep occupying the next levels going up and up each time so right now you should understand that we have the metal ions each one with their electrons and at absolute zero these electrons will be still but let's say at room temperature we will also have the thermal energy so those electrons will also be vibrating as we have seen before actually only the upper orbit's electrons will be able to jump around between the energy levels to understand better let's imagine these electrons in the 2d representation instead of the 3d orbit so now jumping between the levels of the energy would be something like this the more energy they have the higher the jump will be so now if i have a different metal alloy with different characteristics these energy jumps at the same thermal energy input will be on a higher energy level so with the same thermal energy input on the second metal the jumps will be higher at least energetically speaking so now let's see what happens when we join these methods together and create a junction now we'll play a voltage difference between the ends of these wires like this so the electrodes will flow from the left to the right so that means that some electrons from the left metal will go to the right metal but the free electrons of the second metal are vibrating on a higher energy level so now the vibrations are smaller and that represents less thermal energy and that at the same time less temperature so let's put it this way let's give some imaginary values imagine the electrons on the right metal are jumping between the energy levels 5 and 8. so we have three levels of energy difference and also remember these are just imaginary numbers so now the electrons will jump on the metal on the right where the electrons are jumping between the levels of energy 7 and 9. so what do you think that electron will still jump three levels of energy in this case from 7 to 10 or it will only jump the difference of energy so from 7 to 8. well our electron from the left metal didn't get any external energy so its maximum level will still be energy orbit 8. so in this case the jump will be smaller of only one level of energy but what does smaller jump represents as i've told you before the bigger is the vibration of an electron the higher is the thermal energy so in this case since the jump is smaller that means that some thermal energy was lost and at the same time that means that the right metal got a little bit cooler the opposite effect will happen backwards if the electrons are falling on the lower energy orbit they will now gain some thermal energy so the metal will get hotter so i hope this makes sense so that's how we get the temperature difference when we apply voltage at the ends of the union of these wires so what we have inside of a peltier cell are a bunch of different alloys metals like this ones connected in series this is made in such a way that on the right we have one alloy and on the other side we have the other alloy so one side will get hot and the other one will get cool having just one simple wire you couldn't even sense the temperature difference but having a lot of connections in series we could get a decent temperature difference in between so guys we use two pieces of metal inside of a so-called thermocouple to create a voltage from a temperature difference and then we use the filter cell with some metals inside to create a temperature difference from voltage so as you can see one is the opposite of the other we could use thermocouples basically to measure temperature quite precisely different types of thermocouples made out of different types of alloys will give different voltage output and they could go from different temperature range for example this is a k-type thermocouple which would measure up to 1200 degrees celsius on the other hand we could use peltier modules to cool down something there are some makers who made their own portable freezer out of beltier modules and a heat dissipator and some batteries another use for the peltier modules is to use them in reverse so we cool down one side and we heat up the other side and that will create a voltage this time the voltage is way higher because we have a lot of junctions in series and not just one as before so for example space satellites could have a nuclear thermal generator inside and can use that heat to create voltage from the peltier modules and with that supply the satellite for a very long time there are other makers that created a voltage generator from belgium modules with a candle and a heat dissipator so guys this was the thermoelectric effect and more specific the sea back effect and the peltier effect i hope that you learned something new and if you like this video give it a like make sure that you subscribe for more interesting videos also consider supporting my work on patreon so thanks again and see you later guys [Music]

Channel: Electronoobs

Views: 356,642

Keywords: thermoelectric effect, Peltier effect, Seebeck effect, physics, explanation, tutorial, electrons, how it works, freezer, thermocouple, type, animation, electronics, basic, demonstration

Id: PccE4WcfnAw

Length: 14min 22sec (862 seconds)

Published: Sun Sep 20 2020