NTC

kell · 2006-10-27T16:55:50+00:00

I got a heater with a ceramic heating element that has a negativetempco. This kind of bugged me out, but I decided to make lemonade outof the lemon and design a circuit to keep the temperature of theheating element confined in a window.It uses an op-amp (or a comparator, with the addition of a pull-upresistor) and resistors in a bridge configuration is such a way that itregulates current and keeps the resistance of the NTC conductorconstant, which will keep the temp constant also.If the heating element ever gets up to heat (!), its resistance shouldcycle in a narrow range about the valueRs(R2/R1). The feedback resistor on the positive input of the op-ampshould have a much higher value than the resistors in the divider. V in | | ,---------------+---------------------, | | | | / / \ \NTC /R2 /heater \ \ / / | | | | | ,--/\/\/\/---, | | | | | | | |\ | | +-----+--|+\ | 10 |--' | | >------+--/\/\/\/--+--|| | ,---|-/ | |--, | | |/ / | | | \ | / | /15k | \ | \ | /R1 | | | \ | | | / '----/\/\/\/--------------+------+ | | | / | \ | /Rs | \ | / | ...

Oct 27, 2006 61 Replies

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kell 19 years ago

All right, thanks. Your solution seems to be so much better.

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Terry Given 19 years ago

Hi Spehro,

That was fascinating! Xie4xie, lao3shi1. Wo3 mei2you3 han4zi4, wo3 dong3 er4shi2 han4zi4! Wo3 man2 man2 xue2.

Cheers Terry

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