A Multiple Temperature-Control And Alarm System, Based On LM35 Sensor, Using FPGAs and VHDL

Abstract: A multiple temperature-control system, based on LM35 sensor, FPGAs and VHDL, is presented here. The system is capable of providing a series of controls and subsequently activate respective alarm systems. It can simulta- neously monitor three basic temperature-related parameters. The first is temperature range values of specific area or a human. Blue, green and red LEDs light up, to present temperature lowering below lower limit value, temperature re- maining within set values or exceeding upper set value, respectively. If temperature is out of limits buzzer also sounds. Second basic parameter monitored here, is temperature rising or lowering rate within specific time set values and sub- sequent activation of center yellow LED and half right of board LEDs or center white LED and half left of board LEDs, respectively. Finally the third basic parameter monitored with our system, is temperature remaining above upper criti- cal set value or below lower critical set value for a specific time period, thus activating breadboard’s right yellow or white LEDs, respectively. LM35 temperature sensor used here and its analog voltage values act as input to FPGA’s ADC unit and converted temperature values are presented to seven-segment displays. All LED systems activated here, correspond to related external control systems which are activated on a case-by-case basis. The system uses DE10-Lite FPGA board and taking into account that specific time periods, as well as upper and lower temperature limits and tem- perature rising or lowering rates can be set to a variety of values, gives our system the ability of implementation in a wide range of applications such as patient, room, laboratory, industrial or external environment monitoring.

Keywords: LM35 sensor, Temperature, FPGA, VHDL, Buzzer, LEDs.