Saturday, March 14, 2015

Blind Temperature Controller

message: from SJ

for my hobby purpose (pewter small models) i 'm building a kind off rubber press with two hot plate about max: 200degre C. i found your website and studied the different circuits concerning J, K thermocouples, and proportional control that will suits my needs.

I would need more information about one :

- Is the circuit called Blind controller designed for J thermocouple ? as not specified, is not what component value should be adapted?.

- what is function of pot 1K RKE 1W ?

-what does mean RTD i couldn't figure out...?

- Is it possible to use at end of the controller an IC type MOC3041 after Q1 to have zero voltage switching and if so what components should be adapted or add\ removed?

my knowledge in the field are limited question could appear simple... Thanks for understanding

Mail from SJ

In this page Industrial Process Control Circuits

There is a circuit blind proportional temperature controller That is probably what you are referring to.

Blind Temperature Controller
It is for J Thermocouple you can calibrate it with boiling water and Ice. Or if you have the millivolt source you can calibrate it with that.

The 1K RKE 1W is the Dial Potentiometer, You have to fix a dial and Knob. Calibrate the Dial with markings of temperature.

RTD means see here RTD. It is not for this circuit. Unless you want to use it. A 1mA Source is shown in circuit for an 100 ohm RTD sensor.If you are using J type Thermocouple then that is not required.

RTD is more precise, but may be a bit expensive.

MOC3041 can be used, circuit is here. SSR and Zero Crossing Opto-Coplers

Remove the Relay K1. Take two wires from the points that were going to K1 Coil pins 1 and 2. Or take two wires from across diode D1, Observe proper polarity or MOC3041 may go.

The other side of MOC3041 controls Triac and is high voltage and can give shock. Buy and use a SSR

SSR and Zero Crossing Opto-Coplers
Let me know if you have any other doubts.


A words to thank you for the few minutes you spent in answering my questions, " Bravo" for your web site it is particularly well designed and functional...

Yes i might have to contact you again but your explainations are crystal clear so i should not "bother" you more at least for this project.

It is still a long path for me before my project get done, as i built myself all parts of the press,but i won't forget to E-mail you a picture of the result with details.

I could have bought one already made of theses as their price is still affordable, but my opinion is in the internet spirit and lead me to : do it yourself if you can, satisfaction will be your salary. thanks again for your help,

Reply from SJ

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