Electronics > Beginners
How to Build a Temperature Cutoff Circuit for High Power LED
kandrey89:
DrG:
What I have: A remote thermistor on MCPCB, not an IC, must be passive due to extreme heat that could be generated on MCPCB.
What I need: A completely analog solution from an IC that can measure temperature from a remote thermistor and either control the gate of a MOSFET directly or through another IC to perform power cutoff (MOSFET switch) due to over temperature limit.
I've seen the ICs you pointed to and they're just ICs with sensors built-in, I cannot use them, they'd have to be mounted on MCPCB and I don't have space nor the environmental conditions on MCPCB.
I think my best bet so far is to use a constant current source through a thermistor and feed an opamp with preset resistor value that will match my desired cutoff temperature, somehow design in a hysteresis, a few more parts than I'd have liked but when there's apparently available off the shelf...
ogden:
--- Quote from: kandrey89 on February 17, 2020, 07:56:30 pm ---How about IC part number if you're too lazy to reply relevantly.
--- End quote ---
Lazy is one who demands solution on golden plate.
Fully analog solution for you would be thermistor+resistor and comparator with internal reference with MOSFET as switch.
[edit] Something like TLV3012/TLV3011. Other solution would be low cost micropower comparator with two (external) resistors as reference voltage.
Zero999:
There is no magic IC which will do everything requested in the original post. At the very minimum a comparator IC and a gate driver will be required. If it's low speed switching, the gate driver could be omitted, but the comparator would still need quite a few external components to implement the timer and hysteresis.
Mechatrommer:
you can google the aforementioned comparator based... the neatest i can find is this, although not really straight forward, you need to change the 6V zener with the thermistor... and make your own voltage measurement on the resulting voltage divider circuit and make V-temp chart..
the lesser clearer one but spot on temperature control is this...
from and description here... https://www.eleccircuit.com/fan-controller-by-temperature-sensor-using-lm393/
there are many more in google.. for mcu based, you can google how 3d printer senses print head / bed temperature. usually 4kohm (or 47kohm? iirc) high side, thermistor low side...
james_s:
--- Quote from: ogden on February 18, 2020, 04:05:43 pm ---
--- Quote from: kandrey89 on February 17, 2020, 07:56:30 pm ---How about IC part number if you're too lazy to reply relevantly.
--- End quote ---
Lazy is one who demands solution on golden plate.
Fully analog solution for you would be thermistor+resistor and comparator with internal reference with MOSFET as switch.
[edit] Something like TLV3012/TLV3011. Other solution would be low cost micropower comparator with two (external) resistors as reference voltage.
--- End quote ---
Agreed 100%
I don't understand what makes people think they can just show up here and demand a turnkey solution be handed to them. People are happy to help and share knowledge but we are not paid consultants, you have to be prepared to do the legwork yourself or offer something in return. There is no incentive to help somebody who is just going to make demands and then disappear once they have what they want.
If I were trying to solve this problem for myself I'd probably use a cheap 8 pin microcontroller, the firmware to achieve the desired behavior is trivial.
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