What Are Good Alternatives for PTC Thermistors with Sharp Resistance Changes?

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In summary, the conversation is about a new member who is developing a high power electronic system and is looking for a hardware shutdown for over-temperature. They mention using a PTC with a sharp Resistance vs Temperature characteristic and have purchased a kit from EPCOS. They are looking for other manufacturers or kits that offer this feature and have a better control on tolerance. They also mention wanting more options for nominal values. Another member suggests using a bimetal switch as an alternative and provides a link to a product from TI.
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Sparky27
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Hi all, I'm new here so I thought I'd give this a shot.

I'm developing a relatively high power power electronic system and I want a hardware shutdown for over-temperature without going back and revving my PCB too extensively. One effective way to accomplish this is with a PTC with a sharp Resistance vs Temperature characteristic like so:
upload_2016-3-31_10-7-26.png


I've actually purchased this kit shown here: http://en.tdk.eu/inf/55/db/PTC/PTC_Sensors_SMD_chips_standard.pdf

I'm still shopping around but I'm wondering if any of you have experience with PTC selection. Here are my main issues:
1. NTC's generally won't work for what I'm trying to do because they are relatively linear. Effectively what I want is a temperature triggered switch (like shown characteristic). The linked above was the only family of resistors (EPCOS) that I could find with that property. Does anyone know of any other manufacturers or kits that might have this feature?
2. The tolerance range of these ones I've found is HUGE (+/-50%). This will become a digital signal at the end of the day so I can work with it but I'd prefer less slop. Once again, does anyone know of any other suppliers I can go to that will have a better control on tolerance?
3. The nominal values from this kit are very limited (just 110, 470,680,10k) and I'd like more options.Basically, I'm still shopping but thought I'd give it a shot in case any of you out there know your PTC's and more importantly your suppliers.

Thanks!
Sparky
 
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Sparky27 said:
One effective way to accomplish this is with a PTC with a sharp Resistance vs Temperature characteristic
A bimetal switch could be an alternative.
It's simply on/off.
 
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What is a PTC thermistor?

A PTC (Positive Temperature Coefficient) thermistor is a type of thermally sensitive resistor that exhibits an increase in resistance with an increase in temperature.

What factors should be considered when selecting a PTC thermistor?

When selecting a PTC thermistor, factors such as the desired operating temperature range, resistance value, and response time should be considered. Additionally, the circuit's voltage and current requirements, as well as the thermistor's stability and long-term reliability, should also be taken into account.

What are the advantages of using a PTC thermistor over other types of temperature sensors?

One of the main advantages of using a PTC thermistor is its high sensitivity to temperature changes, allowing for precise temperature measurement. PTC thermistors also have a small size and low cost, making them ideal for use in a wide range of applications.

How do I choose the appropriate PTC thermistor for my application?

The appropriate PTC thermistor should be chosen based on the specific requirements of your application, such as the desired temperature range and accuracy. It is recommended to consult with a PTC thermistor manufacturer or supplier for assistance in selecting the right thermistor for your needs.

Can a PTC thermistor be used in both heating and cooling applications?

Yes, PTC thermistors can be used in both heating and cooling applications. When used in a heating application, the thermistor's resistance increases with an increase in temperature, causing it to generate heat. In a cooling application, the thermistor's resistance decreases with an increase in temperature, allowing it to absorb heat from its surroundings.

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