Temperature Detector Incorporating Buzzer Alarm

Brief Introduction

This is a project that is determined to regulate the amount of temperature within boiling water, homes, car engines, and boilers such that when a certain temperature is exceeded the system detects and triggers a buzzer alarm to alert the person in charge.

Working on the Circuit

The figure below shows a well-designed circuit of temperature sensor circuit which has been done using the KiCAD EDA tool. The circuit has an LM335Z temperature sensor, TL071 comparator Op-Amp, and alarm/Buzzer as the main components.

The role of the resistor R1 is to limit the amount of current that goes into the LM3352 IC to the required 1mA. The potentiometer RV1 is used to adjust the output voltage to the IC TL071 IC pin 2 which is the inverting pin. The R2, RV2, and R3 are used as the reference voltage that goes to the comparator pin 3 which is the non-inverting pin. The Resistors R2 and R3 serve as voltage dividers and RV2 is for adjusting the temperature detector sensitivity. The potentiometer RV2 has a resistance range of about 2.8 to 3.3V which is equivalent to a temperature range of 268 to 337 Kelvin.

The user can adjust the temperature as they want since the TL071 IC has a good temperature range from -40 to 100 degrees Celsius. RV3 potentiometer is used to adjust the TL071C output.

Now when IC M337L_S08, U1 detects the temperature less than RV1 is set to, It triggers the pin 2 input voltage to exceed the voltage at pin 3 thus making the output pin 6 high to approximately 9V hence biasing Q1 which switched Buzzer connected at J3 to buzz.

The BOM

• U1 SOT-89-3 1 LM337L_SO8
• J3 PinHeader_1x02_P2.00mm_Horizontal 1 Buzzer Connection
• 3 J2 PinHeader_1x01_P2.00mm_Horizontal 1 9V
• 4 Q1 SOT-89-3 1 BC327
• 5 U2 MSOP-8-1EP_3x3mm_P0.65mm_EP1.68x1.88mm 1 TL071
• 6 J1 PinHeader_1x01_P2.00mm_Horizontal 1 GND
• 7 R2 R_0805_2012Metric 1 8.2k
• 8 R1 R_0805_2012Metric 1 5.6k
• 9 RV3 Potentiometer_Bourns_3339P_Vertical_HandSoldering 1 100k
• 10 R3 R_0805_2012Metric 1 3.9k
• 11 RV2 Potentiometer_Bourns_3339P_Vertical_HandSoldering 1 1k
• 12 R4 R_0805_2012Metric 1 470
• 13 RV1 Potentiometer_Bourns_3339P_Vertical_HandSoldering 1 10k

The BOM has been generated using the KiCAD EDA tool.

We assemble all the component symbols using the KiCAD EDA, then convert them to a PCB layout, complete the design as expected, do PCB routing, size the traces as expected, add vias, and finally generate all the expected fabrication files such as Gerbers, BOM, drill files, and pick and place files.

The PCB 3D Output

Ordering of the PCB Board Manufacturing

Lastly, you can assemble your board at home or consider choosing the best online manufacturers available to fabricate the board for you. Definitely, for me, I would choose some manufacturers for this board.

The best manufacturer that I have always loved and worked with is the PCBWay who have always done quality work and delivered the boards on time as agreed during ordering. The board is ordered online through their website by clicking on the PCBway instant quote page and placing your order by uploading your fabrication files derived from your favorite design software.