PC Heat Alarm Circuit Help

[Kate Manuel]

I've connected this circuit on a breadboard and repeated it 3 times just to make sure that I did it correctly. However, when I plug it into the host PC and I actively increase the temperature of my PC to a high one (around 90degC), it doesn't beep. I also tried changing the VR1's reference voltage a few times. I know that there's power flowing through for there's static-like sounds from the speaker. I just don't know what I'm doing wrong. Any ideas?

(Here's the link to the circuit I'm trying to build: http://www.ecircuitslab.com/2012/05/pc-temperature-alarm.html)

 

[tpetar]

Hello Kate and Welcome to EDABoard,

Try this circuit :

**broken link removed**
http://electrosuite.com/audio/alarm/overheat-detector-alarm.html



Additional circuits:

http://automwiring.blogspot.com/2013/04/basic-lm35-temperature-sensor-circuit.html
http://circuit4diagram.blogspot.com/2013/09/fan-control-temperature-using-sensor.html



Best regards,
Peter

 

[chuckey]

Check the output of the ca3130 pin3 make sure it goes fro 0 ->5V with temperature or twiddling the pot. I think that the loudspeaker has too low an impedance,either use a high impedance piezeo buzzer/sounder, or just for testing disconnect the loudspeaker and connect in its place an ordinary audio amplifier with its speaker.
Frank