speaker protection circuit

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Find this protection circuit:

http://users.otenet.gr/~athsam/protection_2_EN.htm

and like to try on it. The kyt81-122 is difficult to find so can I use a ntc thermo resistor instead. I would think of feeding R3,R2 into - input of IC1a and R1,ntc into + input of IC1a. Would that work? How are we going to test if this part works? If I am going to glue the sensor to a test heatsink and do the calibration or testing, I might never able taking it off and glue it to the working one? Can I use a pot for R3 so as to adjust the temperature for cut-off.
 
diyAudio Member
Joined 2002
bigpanda said:
The kyt81-122 is difficult to find so can I use a ntc thermo resistor instead. I would think of feeding R3,R2 into - input of IC1a and R1,ntc into + input of IC1a. Would that work?

Hi,
Yes.
How are we going to test if this part works?

With cheap thermometer or with your fingers.

Bolt NTC on a small sheet of metal on one side. Use your soldering iron and warm up the opposite side. Put your finger on the NTC. Lift your finger up when the NTC gets too hot for you; this means that the the temperature is about 65-70C. Immediately measure NTC resistance. Use the same value for R3. Simple, right?;)

If I am going to glue the sensor to a test heatsink and do the calibration or testing, I might never able taking it off and glue it to the working one?

I wouldn't be in favor of this. A better idea is to use a small piece of metal bolt and a screw. Use thermal grease between the heatsink and NTC.


Can I use a pot for R3 so as to adjust the temperature for cut-off.

Yes.

Regards,
Milan
 
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