Power Supply thermal Management
3.2 Thermoelectric cooler (TEC)
- Introduction
In our previous article, we have seen the selection parameter of the heat sink and cooling fan. In this article, we will discuss Thermo Electric Cooler (TEC). TEC can be used in heating or cooling system in an application where temperature stabilization or cooling below ambient temperature is required. Here we will use the TEC for water cooling application and discuss pros and cons of TEC.
- Principle
TEC works on the principle of Peltier Effect which states that if a DC current is applied across two dissimilar materials causes a temperature difference.
For this purpose, a thermoelectric material is used which is popularly known as Peltier.
The Peltier is made by using two ceramic wafers with P and N doped semiconductor materials connected in series and sandwiched between them. The N-type semiconductor has an excess of electrons and P-type has a deficit of electronics. By increasing the no. of P and N semiconductors more temperature difference can be created.
The amount of temperature difference developed across the Peltier is proportional to the current following through it. The negative side of the Peltier gets cooler while the positive side becomes warmer. By reversing the current flow direction we can make cooler side hotter and warmer side cooler.
- Parts needed for normal functioning of Peltier
A typical Peltier can generate a temperature difference of 70° between its two surfaces. For normal functioning of Peltier we need to remove heat from its hot side otherwise the Peltier will reach in an equilibrium state and do nothing. So we need a heat sink at its hotter side for extracting the extra heat and also we can use a cooling fan with the heat sink to spread the heat out in the surrounding.
- Peltier application
- Heating
- Cooling
- Power generation
By Peltier, we can convert the electrical energy into heating or cooling and vice-versa. The conversion of temperature into power is called as Seebeck Effect.
- Thermal Schematic of our system
- Circuit connection
- Parts required
- Peltier- CP150
- Heatsink and 12V DC Cooling Fan
- Aluminum water cooling block
- Power source 12V/10A
- Driving the Peltier
Basically, Peltier needs a current source for its operation, but below are the following methods through which we can operate Peltier
- Current source
By applying a constant current to a Peltier we can generate a temperature difference across it. For measuring the amount of current needed to generate a specific temperature we can use the characteristic curve which is mostly given in the Peltier datasheet like below one
- Voltage source
If we have a voltage source then we can operate the Peltier by PWM (Pulse Width Modulation) signal. By varying the voltage we can control the current flow through the Peltier.
- Peltier with driver
Depends on the application of Peltier we can operate Peltier with or without its driver circuitry.
- Peltier Mode of operation
- Open thermal loop system
When Peltier is operated without any feedback network then this system is known as Open-loop system. In open loop system, we cannot regulate or control the temperature developed across Peltier.
- Closed thermal loop system
For maintaining a constant temperature at Peltier we can use a driver, the driver is simply an H-bridge circuit.
When any of the Peltier surfaces get hotter and cooler above its set point then Peltier will detect this change by a temperature sensor. The driver in the response to this, change the direction of the current flow and this will maintain a constant temperature.
- Experimenting with Peltier
We have used the Peltier in open loop system for cooling water; for this, we mount the Peltier with a cooling fan at its hotter side and a two-way aluminum water block at its colder side.
For the power source, we have used a voltage source and below are its results.
Results
Input voltage |
Output current |
Temperature difference (Between Hot and cool surface) |
12V |
7.15A |
10° |
- Application
- CCD cameras
- Laser and Amplifiers
- Refrigerator and water dispensers
- Avionics
- Advantage
- Small size and weight as compared to the normal mechanical system
- Unlike heat sink provides cooling below ambient temperature
- Ability to cool and heat at the same time
- Precise temperature control by closed-loop thermal control.
- Can be used with DC power supply or PWM signals
- Can generate electrical power also
- Reliable
- Eco-friendly does not generate any gas like a conventional refrigerator
- Disadvantage
- Need a heat sink for dissipation of extra heat from the hotter side, hot side temperature should not go beyond 60°
- Require more TEC module for large power generation.
- Point to ponder
- Always use a heat sink and cooling fan to the hot side of Peltier, otherwise, the Peltier will malfunction
- Power the Peltier under its operating range only.
- The recommended power source is a current source or PWM signal.
- The thermal electric material is recommended for proper contact between heat sink and Peltier.
- Use brackets for mounting the water cooling block to the Peltier, this will create extra pressure and provide better contact.
- Real-time picture
Project Source Code
Project Source Code
### //Program to /* @Project: Browser_client_controls_Server_light @Hardware used: ESP8266-01 CP2102 or Arduino UNO (as a USB to Serial converter) LED & 220E resistor External Power supply to provide 3.3V to ESP8266 (Optional) @Brief Introduction: In this application, we have used ESP8266 as our CoAP server & Copper (Cu) as a CoAP client (it is supported with mozilla firefox browser.) The client sends GET, PUT request to the server and server controls the light on the basis of receiving PUT message. For more details, please refer our Article: Browser client controls Server light */ //Include Libraries #include <ESP8266WiFi.h> //Include the ESP8266 library to connect the server to the WIFI #include <coap_server.h> //Include the CoAP server library to connect the server using CoAP protocol /* * Callback Function Declaration: This is a callback function, whenver server receives any get or put request, * the server responses accordingly through this function. * This Function takes the packet (Message), IP address & port of the CoAP client & observe the request on the particular service. */ void Light_control(coapPacket &packet, IPAddress ip, int port, int obs); //Create an instance of CoAP server coapServer coap; /* * Access point SSID & PASSWORD * Change this according to the network */ const char* SSID_of_Router = "NOT UR WIFI"; const char* PASSWORD_of_Router = "marketing"; //Connect LED to the GPIO2 of ESP8266 & for reading the led state at the client end, initialize the Variable for it. int light = 2; bool Light_state; //Define the Callback function void light_control(coapPacket *packet, IPAddress ip, int port, int obs) { char p[packet->payloadlen + 1]; memcpy(p, packet->payload, packet->payloadlen); p[packet->payloadlen] = NULL; Serial.println(p); String message(p); if (message.equals("0")) { digitalWrite(light, LOW); Serial.println("light is OFF"); } else if (message.equals("1")) { digitalWrite(light, HIGH); Serial.println("light is ON"); } char *Room_light = (digitalRead(light) > 0) ? ((char *) "1") : ((char *) "0"); //The server look for the observe flag or GET request from the client if (obs == 1){ coap.sendResponse(Room_light); } else{ coap.sendResponse(ip, port, Room_light); } } void setup() { yield(); //Start the serial Monitor at specified baud Rate as ESP8266 needs 115200 buad rate to communicate using serial Serial.begin(115200); //Initiate the connection of ESP8266 to the Router WiFi.begin(SSID_of_Router, PASSWORD_of_Router); Serial.println(" "); Serial.print("Connecting to...... "); Serial.println(SSID_of_Router); //Wait for the connection establishment while (WiFi.status() != WL_CONNECTED) { yield(); Serial.print("."); } Serial.println(""); //If ESP8266 Wi-Fi is connected to the Router then //we will see the IP address assigned to the ESP8266 Serial.println("WiFi connected"); Serial.println(WiFi.localIP()); pinMode(light, OUTPUT); digitalWrite(light, HIGH); Light_state = true; // add server url endpoints. // We can add multiple endpoint urls. coap.server(light_control, "Room_light"); //Initiate the Connection of ESP8266 as a CoAP server & the port on which server is listening. coap.start(); coap.start(1234); } void loop() { coap.loop(); delay(1000); } ###
Circuit Diagrams
Project Datasheet
Filed Under: Electronic Projects
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