As I promised, I uploaded the project files for my first version curve tracer. I am finally had some time to clear out the arduino code and make a proper schematic for the curve tracer. Everyone can find and download the files.
Some instruction and explanation:
R1 is a current limit resistor which is setted to 2K ohm.
The R2 resistor is a current sense resistor, I had to put in, because a did not have enough signal to drive the op amp. It is setted to 93.5 ohm.
R3 and R5 are the set resistors to the gains.
I used a TLC2721P precision OP-Amp for create the signals, what did need for the arduino. The R4 and R6 are voltage dividers, in ideally these are set in to the middle, but in my case I had to adjust these to set the line in the middle on the screen.
First have to download the sketch to the arduino and put together the circuit. After have to set R1 and R2 to the correct values.
Then you have to set offset of the Op-Amps (R4 and R6), if you have everything right, you have to see a horizontal line or dot somewhere on the screen. Then you adjust it to the middle with R4 and R6. If you short the probes you shoud see some deflection to vertically.
If the line or dot is in the middle, after you have to adjust the gain with R3 and R5. After all you shoud see a horizontal line when nothing is connected to the probes, when you short the probes you shoud see a vertical line in the middle.
After all these setting you are ready to use the curve tracer.