You need to increase voltage that supply opamp.. opamp doesn't have voltage high enough going to it to be able to make it's output high enough.
Try making V1 15-20 V and try..
Yes I did that - see the post you answered to: "Giving the opamp a higher voltage also does not change much, see attached pic."
I should have worded it better, sorry.
I gave them their own voltage supply of 15 or 20 Volt (V3), and let V1 at 9V. In the picture CCL_3c.png above, both opamps had 20V supply.
Also you have to make resistor smaller and use smaller input voltage as control.. If you have 4V on 4A on a 1 Ohm resistor it is 16W.. that's a lot...
For smaller currents let's say 1A it is ok at only 1W..
You mean making R1 smaller? And making the input voltage for the second opamp on the noninverting input (+ on the left side) smaller? I did that, see the above post: I changed the dividers R2 & R3, so that the opamp input voltage on the noninverting input (+) is lower, then it somewhat works.
Also, please try some other opamp model.. I downloaded one you use and it seems to be behaving funny..
I just tried like 20 different opamps (also LT1677) and they all show the same characteristics.
The datasheet of the LM324 shows that the inputs do not work if their voltages are above (the supply voltage minus 1.5V) which is 7.5V in your circuit. But your input is 8V so of course the opamp does not work.
If you increase the supply voltage V1 of the opamp then the inputs will work properly.
Only the first opamp might have input voltages >7.5V if the potentiometer is <~20%, its output at 10% potentiometer value is ~8V. The second opamp that is the relevant one never has input voltages anywhere near 7.5V - see CCL_3c.png above: This is what happens when both opamps have 20V supply. The input voltages at the second opamp are maximum 4V (U+ and U- in the picture).
The datasheet for the Mosfet shows that it completely turns on when its gate to source voltage is 10V. But since the value of R1 is so high at 1 ohm then for 4A though it its power is 16W (!) and its voltage is 4V and the input to the Mosfet must be 14V. then the supply voltage V1 for the opamp must be 15.5V or more.
Back to the setup from my original post and both opamps having 9V supply (which I've shown does not make a difference to them having 20V supply when looking at the current through R1). The mosfet's maximum gate-source voltage is 7V.
Hee, hee. Don't make the resistor smaller as was said, instead reduce its value to 0.15 ohms or so. Also the voltage from the pot must be reduced with a series resistor making a voltage divider.
I don't quite understand this sentence. The resistor R1 was 1 ohm, you tell me not to make it smaller but instead to reduce its value to 0.15 ohm - for me that is smaller than 1 ohm.
But the overall characeristics of the current/voltage at R1 does not change no matter what value R1 has.
Thank you for your answers