science fair

[deleted-147265]

Im making prototype of a device that will sense if a child is in an overheated car. I will have a pressure and temp sensor once both are activated the circuit will be comlete i need to know how to finish the circuit when the temp sensor goes above a certain temp

[rmarz]

Saumilkhadilkar - I understand the temperature sensor in this experiment, not sure what role the pressure sensor plays. One of the tasks any alarm circuit has to perform is how to interface the output reading of the sensor to the real world so that an alarm warning could be activated. In a simple bimetal thermostat, for example, the bimetal element is actually a SPST switch and can be wired directly to the sounding or alerting device (assuming it is powered by electricity). If your sensor is an electronic element like a thermistor or thermocouple, the interface is very dependent on the sensor. Is the output a varying resistance value? If it is, you need some circuitry that that evaluates that 'when this resistance is present' the circuitry determines that the condition for alarm is met and is activated. There are a number of mechanical thermal switches such as 'fan switches' that you might be able to salvage. Older mercury thermostats should never be used because of the mercury issue. Tell us more about your sensor and we might be able to be more helpful.

As an aside, you might write this up as a different kind of alarm such as a freezer alarm to protect food if refrigeration fails, or a frost alarm to help protect outdoor plants. The idea of protecting a child in an overheated car is probably not the best. Children should not be left unattended in cars no matter how effective the alarm system might be.

Rick Marz

[deleted-147265]

Thank u by the way the role of the pressure sensor is to see if the child is in the car or the alarm would go off whenever the car is hot

[rmarz]

Saumilkhadilkar - I understand. I misunderstood it to be an air pressure sensor, not a mass sensor.

Rick Marz