hi Sourc
Check this simulation for -100C change over.

Do you follow it OK.?
I would recommend 0.1% tolerance resistors and R5 be 100 Ohm 20 turn trim pot, for calibrating.

E
View attachment 272418

Im reading, im reading, I dunno if I understand the graphic now, -120v? where is the change? 0.01ohm? Im trying but this last reply is a bit confused for me.

 

Hi S,
Read the Notation on the Plot NOT -120V, but -120C degrees, the scale is Degrees.

The switch On temperature for the relay is -100Cdeg rising , if you want the relay to switch Off at a lower than -101C, falling, reduce the value of R2.


What don't you understand about the plot.???

E

 

Hi S,
Is this any easier to follow.?
Lowered the relay drop out temperature.
E

 

Hi ericgibbs , I am here again for the holidays, now we are going to order nitrogen again and in these days finish your prototype, sorry for being absent but it was my holidays and I have completely disconnected.
[READY]



I don't have a 60 ohm res and 1Meg, I will use a 148 (100+48) ohm and a 500k ohm and try to test it with a heat gun.
Today I said you the results.

 

Hi @ericgibbs , I had tested with the hot gun, I set the reference resistance in 120ohm, so when I heat it, the Vin((-V)-(+V)) is > 0 and the relay is ON (I have set the max amper in 40mA) and It's work, when it need to OFF again, it doesnt work. Anyway, this monday I will order the nitrogen and test it with your real values.
I needed a lot of time to understand the LM339 xd hahaha but thanks a lot, it only need a bit more work.

 

hi S,
I thought we agreed that reference resistor was 60R.?
E

 

hi S,
I thought we agreed that reference resistor was 60R.?
E
View attachment 275418

I have order the nitrogen, but for now Im using a 120ohm resistor to test with a hot gun

 

@ericgibbs I have a question, the arduino mudule relay, have 3 pins (S, +, -), in my last circuit I join S with + and its work, do u think your circuit can resist that? What current do u calculate in transistor output? Im getting very high current.

 

hi S3.
Do you have a type number for your Relay Module or a link so that I check the details.?
E

@Sourc3
What is the voltage of your power supply and the working voltage of the relay module.?


If your module is of this type, they are only 5V relay coils

 

hi S3.
Do you have a type number for your Relay Module or a link so that I check the details.?
E

@Sourc3
What is the voltage of your power supply and the working voltage of the relay module.?


If your module is of this type, they are only 5V relay coilsView attachment 275671

@ericgibbs I think I have it, I think this relay come with the diode and transistor like you posted.

So I have removed this part and it works, I have set 24 volts (To feed the solenoid too). And connect 24 volts to S(signal) and +(positive)

 

@ericgibbs I think I have it, I think this relay come with the diode and transistor like you posted.
View attachment 275716
So I have removed this part and it works, I have set 24 volts (To feed the solenoid too). And connect 24 volts to S(signal) and +(positive)

Im using a potentiometer to simulate resistance bridge.

 

Hi S3,
Pleased to hear you have succeeded in making it work.
Let me know how it goes when you get the liquid nitrogen to carry out the final test.
E

 

Hi S3,
Pleased to hear you have succeeded in making it work.
Let me know how it goes when you get the liquid nitrogen to carry out the final test.
E

Me too sir, thank you very much for your constant help. I'll send you a video when I have nitrogen and we can see it live.

 

I worked with LN2 and you need a solenoid designed for LN2.

Way back in post #9 I mentioned that. Normally solenoids designed for cryogenics specify it in their data sheets. Does the label on the solenoid you show specify it works with LN? I had assumed you were already working with the LN2.

Ron

 

Way back in post #9 I mentioned that. Normally solenoids designed for cryogenics specify it in their data sheets. Does the label on the solenoid you show specify it works with LN? I had assumed you were already working with the LN2.

Ron

Yeah @Reloadron , its a spececific solenoid for LN2. Thats no problem. We arent go to order LN2 yet, this task has been delayed until mid-October, so we don't go to order LN2 to test it.

 

Yeah @Reloadron , its a spececific solenoid for LN2. Thats no problem. We arent go to order LN2 yet, this task has been delayed until mid-October, so we don't go to order LN2 to test it.

OK, that's good. Please do let us know how things work out.

Ron

 

OK, that's good. Please do let us know how things work out.

Ron

Im sure that the first persons to know that are u, the people of that post.