(SOLVED) Control solenoid valve with Arduino or with circuit

ericgibbs

Joined Jan 29, 2010
18,766
hi,
The diode is just to clamp the back EMF created from switching the relay inductive coil Off.

A general purpose diode with a rating greater than 100v and say 100mA will be fine.
E
 

Thread Starter

Sourc3

Joined Dec 2, 2021
81
hi,
The diode is just to clamp the back EMF created from switching the relay inductive coil Off.

A general purpose diode with a rating greater than 100v and say 100mA will be fine.
E
Ahh nice, I thought that for my circuit, maybe I can get some diode from some board, I have thousand here.
 

Thread Starter

Sourc3

Joined Dec 2, 2021
81
hi,
The diode is just to clamp the back EMF created from switching the relay inductive coil Off.

A general purpose diode with a rating greater than 100v and say 100mA will be fine.
E
I will SIM the circuit first, I dont understand some points, I will post the result in a moment.
 

Thread Starter

Sourc3

Joined Dec 2, 2021
81
hi,
The diode is just to clamp the back EMF created from switching the relay inductive coil Off.

A general purpose diode with a rating greater than 100v and say 100mA will be fine.
E
Ok, so u need to have the relay in Normally Open mode, so the difference between 20ohm and 60ohm(steam nitrogen) is closed and when there is no nitrogen (60 ohm), its should be activated.
 

ericgibbs

Joined Jan 29, 2010
18,766
hi Sourc,
Most relays have change over contacts,
ie: one normally closed and the other normally open.
Change over when energized.

Let me know the result of your simulation.
E
 

ericgibbs

Joined Jan 29, 2010
18,766
Hi S,
The circuit simulation I posted works as you asked.+40C relay ON, less than +40C relay OFF.

I have decreased the hysteresis to about 1C.

Why do you say it didn't work as expected.??
also, why was the 115R changed to 60R.??

E
EG57_ 07.png
 

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Thread Starter

Sourc3

Joined Dec 2, 2021
81
Hi S,
The circuit simulation I posted works as you asked.+40C relay ON, less than +40C relay OFF.

I have decreased the hysteresis to about 1C.

Why do you say it didn't work as expected.??
also, why was the 115R changed to 60R.??

E
View attachment 272335
Aaaah I understand now the confusion, when I said 40, I refer to Ohm not to Celsius.
I mean, need ON with 40-60 ohm or superior, and OFF with less than that. That is translated to ON in -50C to -100C and OFF with less than -100C. That why the reference resistor should be around 60ohm. (Steam/vapors nitrogen are -90C aprox).
 

ericgibbs

Joined Jan 29, 2010
18,766
hi @Sourc3

So to simplify, when using a PT100

Relay Off when lower temperature than -100C
and
Relay On when temperature higher than -100C

Can you confirm this.?

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A 10 Jul. 28 08.27.png
 

ericgibbs

Joined Jan 29, 2010
18,766
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
EG 1289.png
 

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