Digital temperature monitoring/control circuit
The digital temperature control circuit is a precision temperature controller for medical, industrial and home applications. This system is better than the analog system / thermostat with poor accuracy. For example, it can be used to control the temperature of an incubator where maintaining an accurate temperature is very important.
digital temperature control system
The proposed digital temperature control system provides the temperature information on the display, and when the temperature exceeds the set point, the load (ie the heater) is turned off. In this project, the lamp is provided as a load for display purpose. Below is a schematic diagram of a digital temperature control system.
schematic diagram of digital temperature controller
The proposed digital temperature control system uses a microcontroller of the 8051 family, which is the heart of the application. The display unit consists of a four-seven-segment display, a temperature sensor and is connected to a microcontroller.
The digital temperature sensor is connected to the microcontroller to sense the temperature conditions. This system also provides four pressure switches for adjusting temperature settings.
Then the microcontroller continuously polls the temperature information through the digital temperature sensor and displays on the 7-segment display unit and automatically turns off the lamp, when the corresponding temperature exceeds the set point.
Hardware Requirements
Transformer (12-230 VAC)
Voltage Regulator (LM 7805)
the average
purifier
microcontroller (at89s52/at89c51)
Temperature Sensor DS1621
Push buttons
Show 7 pieces
BC547
resistors
Capacitors
1N4007
rotation
microcontroller (AT89S52)
The Atmel AT89S52 is a powerful 8051-based microcontroller that provides a highly flexible and cost-effective solution to a multitude of embedded control applications.
The AT89S52 provides the following standard features:
8 KB of flash
256 bytes of RAM
32 I/O lines
Monitor timer
data indicator
Three 16-bit counters
Geometry two-tier county of six vector
Bi-directional serial port
On-chip oscillator, clock circuit
A pin diagram is shown below.
8051 microcontroller
8051 microcontroller
Temperature Sensor DS1621
A sensor is a device that receives and responds to a signal or stimulus. The sensor can only convert the received signal into electrical form.
The DS 1621 temperature sensor offers the following standard features:
Measurements do not require external components
Measures temperatures from -55°C to +125°C in 0.5°C increments (67°F to 257°F in 0.9°F increments)
The temperature is read as a 9-bit value (transfer 2 bytes)
Wide power supply range (2.7V to 5.5V)
Converts temperature into a numeric word in less than 1 second
Thermostatic settings are user selectable and non-volatile
Data is read from/written via a two-wire serial interface (drain open input/output lines)
Applications include temperature controllers, industrial systems, consumer products, thermometers, or any temperature sensitive system
It is an 8-pin DIP or SO package
Description Pin
DS1621 Pin Description
DS1621 Pin Description
SDA - 2-wire serial data input/output
SCL - Wired Serial Clock
GND - Earth
TOUT - thermostat output signal
A0 - chip address input
A1 - Enter slide title
A2 - chip address input
VDD - power supply voltage
The functional schematic diagram of the DS1621 is shown in the figure below.
The DS1621 provides a 9-bit temperature readout, which indicates the device's temperature. The thermostat output signal (TOUT) activates when the device temperature exceeds a user defined temperature (TH).
The output remains active until the temperature drops below a user set temperature TL, allowing for any necessary slowdown. User-defined temperature settings are stored in non-volatile memory so that parts can be programmed before they are fed into the system.
Temperature settings and temperature readings are sent to/from the DS1621 from the microcontroller via a simple two-wire serial interface (I2C).
temperature measurement
The DS1621 measures temperature using a bandgap based temperature sensor. Delta Sigma Analog to Digital Converter (ADC) converts the measured temperature into a digital value calibrated in Celsius or Fahrenheit.
The temperature reading is provided in a complementary reading of 9 bits, two by issuing the temperature reading command. Data is sent through the two-wire serial interface - MSB first (I2C Serial Communication Interface).
Show the seven basic parts
This version is a common version of the anode. This means that the positive portion of each LED is connected to a common point which is pin 3, Vcc in this case. Each LED has a negative leg attached to one of the device's pins.
7-segment LED display
To make it work, you need to connect pin 3 to 5 volts. Then to make each part light up, connect the ground pin that led to ground through the resistor. It can also be used through any sinking position microcontroller port eg. PORT 0 in 8051 series microcontroller.
Programming
We used the C language to write the application code and compiled it using the KEIL micro Vision (IDE) compiler. After you finish writing the program, this code will be converted to hexadecimal code in order to drive the microcontroller. The generated hex code is burned into the microcontroller using an appropriate programmer.
A 5V power supply is required to power the system, connected to 40 pins of the microcontroller and GND connected to 20 pins. Pin 1.0 to 1.3 is connected from port 1 to the push buttons. Pins 3.5 to 3.7 of the microcontroller connect to 1, 2, 3 of the DS1621 temperature sensor respectively.
digital temperature controller schematic diagram
Pin 0.0 to 0.6 from port 0 of the microcontroller is connected to a 7-segment display. Pin 2.0 to 2.3 of port 2 of the microcontroller is connected to the transistors. Pin 2.4 is connected to another transistor BC547 that drives the relay.
The project uses a DS1621 digital temperature sensor which is connected to a microcontroller. The 8-pin IC surface senses the ambient temperature to sequentially present digital data at pin 1, which is displayed from the microcontroller by 4 common 7-segment anode display units all connected in parallel to port "0".
Four push-button switches are connected to the microcontroller with pull-up resistors to help program the exact temperature as desired. The output from the microcontroller at pin 25 drives the transistor which in turn drives the relay that turns the heater on or off to maintain the temperature.
However, the project uses a lamp instead of a heater for illustrative purposes. The lamp will be on normally to be turned off once the set temperature is reached.
digital temperature control applications
Here are some examples of applications that you should pay special attention to.
External uses involving potential chemical contamination or electrical interference
Nuclear power control systems, combustion systems, railway systems, and aviation systems
Medical equipment, amusement machines, vehicles, safety equipment, installations subj
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