Op amp temp control - help wanted....
What I wanted was a thermostat of sorts to control the cooling of a heatpipe,
The actual temps are irrelevant what I need is the difference between 2 sensors (one cold, one hot.) the hot end of a heatpipe is in a variable temp environment (so it gets hot and cooler.) I need to make sure the cold end is always colder. so if the hot cools to within x degrees of the cold i want operate a relay to start a cooling circuit.
I really only wanted one unit ( a prototype , I suppose.) But quotes to get this working varied greatly, some running into thousands.
However one person did point in a direction...though not necessarily the right one ! He said :-"My guess is that yoiu would get close enough putting the thermisters in series from a 5v rail and comparing the mid voltage to reference using an OP amp - and drive the relay from that. I suggest you experiment with this."
Sounds simple enough...except my knowledge of Op amps is about the same as brain surgery !!!
I only want to use simple NTC thermisters 10k±1% 3435°K –50 to 90°C
The relay ideally needs to control an output of 16v 8.5 amps but if it's easier a 240v 10amp can be used so long as it can be triggered.
I only need a small control range 0º-10º or maybe 12º between hot and cold sensors.
I really would like to solve this if I can....any ideas gratefully welcomed.
What I wanted was a thermostat of sorts to control the cooling of a heatpipe,
The actual temps are irrelevant what I need is the difference between 2 sensors (one cold, one hot.) the hot end of a heatpipe is in a variable temp environment (so it gets hot and cooler.) I need to make sure the cold end is always colder. so if the hot cools to within x degrees of the cold i want operate a relay to start a cooling circuit.
I really only wanted one unit ( a prototype , I suppose.) But quotes to get this working varied greatly, some running into thousands.
However one person did point in a direction...though not necessarily the right one ! He said :-"My guess is that yoiu would get close enough putting the thermisters in series from a 5v rail and comparing the mid voltage to reference using an OP amp - and drive the relay from that. I suggest you experiment with this."
Sounds simple enough...except my knowledge of Op amps is about the same as brain surgery !!!
I only want to use simple NTC thermisters 10k±1% 3435°K –50 to 90°C
The relay ideally needs to control an output of 16v 8.5 amps but if it's easier a 240v 10amp can be used so long as it can be triggered.
I only need a small control range 0º-10º or maybe 12º between hot and cold sensors.
I really would like to solve this if I can....any ideas gratefully welcomed.
Last edited:
