I sense the current using connector j2 (who is connected like your schematic on a big heatsink off the pcb) .
I use the NXP buk652R7-30c fet 30V max 200W @25 deg. Celsius.
My Resistor is : Ohmite TEH100 W 1ohm
it is mounted on a ELV LK-40 heatsink capable of 100W when assisted whit the normal fan. 0,73 K / W @ 6.5 CFM
I bought a new fan that does 24 cfm at max speed (delta FFB0412SHN ) 6W 13000 rpm.
My specs are just to try some supply's of mine. My main Agilent psu does 30V @ 3A and it would be nice to fully test it.
My design got some inspiration from jjoster and dave.
The test pcb is beeing manufactured as you speak [for free
] i will find / fix the problems after it gets back (a week or so) .
U7 is actually on the heatsink, not on the board.
U1,2 are on a heatsink , i just didn't make it 3d.
Reply's :
I added the switch (S3) because i rarely would be going over 5 amps.
And i will replace the output cap of the voltage regulator whit a bigger one.
The LM36 just gives a ballpark figure of the temperature. I don't need it to be super exact.
The opamp (one lm324N ) is connected to the top rail of 12V and bottom rail of GND.
I will replace the 1n4007 whit a faster equivalent . I will test if the gate capacitance gives me a hard time. If so i will solve it accordingly (bodge it) . The ADC could give me a hard time because of noise but i will have to experience it first hand and solve my mistake than.