hi,
Please post your latest diagram and sim results.
E

Added:
LTS sim using the correct Thermistor equation rather than a linear source.
Our results now match.

 

hi,
Please post your latest diagram and sim results.
E

Added:
LTS sim using the correct Thermistor equation rather than a linear source.
Our results now match.

Ok, sorry for waiting so long but I figured out how to import that transistor into ORCAD and managed to simulate the project with it. Worth mentioning that I didn't swap the resistor values like you did since, according to my math, it's supposed to be like this. Nothing really changes besides some mV voltages but, for instance, I get close to 5V (5.01V) on TP1 with my resistor values than with the ones you posted (4.88V).

Anyways, I think our results match, yes! I'm trying to troubleshoot the AD output part now. (EDIT1: Just noticed that the commutation point went up to 100C and not 95C, something's probably wrong with the relay since the outputs are fine)

 

hi,
Downloaded your circuit, thanks.
I would suggest R19 be increased in value, say 47k or 100k, the existing 10k will give a 'wide' hysteresis value.
E

I see that on one of your waveform images, that the 95C to 150C, does not start at 0V == 95C.

 

hi,
Downloaded your circuit, thanks.
I would suggest R19 be increased in value, say 47k or 100k, the existing 10k will give a 'wide' hysteresis value.
E

I see that on one of your waveform images, that the 95C to 150C, does not start at 0V == 95C.

I went through my calcs and figured out that at 95C the voltage was 3.30V and not 3.25V. I re-did my calcs so I could find the proper resistor values for signal conditioning 1 / 2 circuits. Turns out, values changed a bit, so I'll attach the updated circuit so you can download it. Worth mentioning that I also changed my Vref voltage at signal conditioning circuit 2 to 3.30V instead of 3.25V, aswell as the R19 value you talked about to 47k.

I'm still finding some problems:

• On signal conditioning circuit 1 the voltage is 200mV = 55C. I wan't to know if it's MY error or if It's something you always need to take into account since the circuit isn't running in a perfect world.
• On signal conditioning circuit 2 the voltage is 4.9V = 150C. Like above, is it my problem or something that is going to happen no matter what? (Worth mentioning that: I'm not looking to have a circuit running at 100% when my calcs don't back it up. I prefer to have this output and explain that It was supposed to reach 5V but it doesn't since this and that rather than reaching 5V and not supporting my case with calcs).
• On the AD output, besides 200mV == 55C and not 0V = 55C (explained on point 1), the first graph doesn't reach 5V since it ends at 90C instead of 95C. My professor warned us that we would have a small temperature gap inbetween the 2 graphs (95C --> first graph / 95C -> second graph) but nothing major like this (it would be a 1 or 2 temperature difference, not 5).
• On the AD output, the second graph doesn't reach 5V because of what happens on point 2.

 

hi j,
What is the simulation period on those images.?
That sloping transition of the AD_Output image is not what I would expect to see.??
E

 

hi j,
What is the simulation period on those images.?
That sloping transition of the AD_Output image is not what I would expect to see.??
E

What do you mean by simulation period? Im simulating according to temperature, not a time domain simulation, so my parameters are [55-150]C with 5C increments.
The ad output is indeed weird.

 

hi,
Try it with 1C increments, using a 5C inc may be causing that artefact.
E

 

hi,
Try it with 1C increments, using a 5C inc may be causing that artefact.
E

I will turn my PC on and get back to it. Will edit the post in a min. In the meantime, can you explain why did we turn up the value of that resistor from 10k to 47k? Didn't understand what you meant by hysteresis, even though my professor talked about it. Also, why do I need a Diode connecting the 2 coil branches and why is one directly connecting to a +12V source?

EDIT1: Lol It works! How could you know that the increment was the problem???? It's literally the greatest news I could have gotten! THANK YOU!

 

hi j,
Pleased to hear you have a good result.
One of the problems with most simulators they create artefacts in the plots they produce.

E

Footnote:
By splitting the Vout into two 'amplified' signals it will not increase the accuracy as you posted earlier, it will only increase the resolution of the ADC values.

Try with 0.5c or if possible 0.1C increments.

 

By splitting the Vout into two 'amplified' signals it will not increase the accuracy as you posted earlier, it will only increase the resolution of the ADC values.

That's what I meant, I'm sorry.

Try with 0.5c or if possible 0.1C increments.

I will, thank you!

Is there any way you could explain my previous comment's questions? Whenever you got the time ofc, I can't really ask for more than what you already did!

 

In the meantime, can you explain why did we turn up the value of that resistor from 10k to 47k? Didn't understand what you meant by hysteresis, even though my professor talked about it. Also, why do I need a Diode connecting the 2 coil branches and why is one directly connecting to a +12V source?

hi,
Look at this PDF to understand hysteresis.

Ref the diode, note a relay coil is effectively an inductor, so look up Lenz's Law regarding 'back emf'.
The diode protects the transistor from being damaged by this back emf.
E

 

hi,
Look at this PDF to understand hysteresis.

Ref the diode, note a relay coil is effectively an inductor, so look up Lenz's Law regarding 'back emf'.
The diode protects the transistor from being damaged by this back emf.
E

Will read it, it's important to know my facts so I can explain the project properly.

Thanks a lot. You helped me before and you helped me once again. Wish you all the best!