- Joined May 16, 2023
Your source sinewave is 12Vpk not 12Vrms, so the maximum rectified DC voltage is about 10.8V.what am I doing wrong?
Sorry, I have not seen that, after change sin amplitude it shows 1,6 v / 13,50
Hi,Thank you all
Below is a sim that compares the two options, showing the difference in linearity:going for just 12v output you could change the pot to a 2.5k value and get closer to what you need. You could put a 5k resistor in parallel to the 5k pot also, which will give you the max of 2.5k, although the voltage adjustment will not be perfectly linear with the pot knob rotation angle using a regular linear taper pot. It probably won't be too noticeable though as the resistance with pot rotation angle will be only mildly nonlinear.
Below is a sim that compares the two options, showing the difference in linearity:
The 5k linear pot with a 5k resistor across it outputs 1/2 the maximum voltage (green trace) at the 33% pot rotation point (horizontal axis) instead of 50% for the 2.5k linear pot (yellow trace).
View attachment 294382
Hello there,An LM317 simulation uses only "typical" specs. But if you build the circuit, some devices have a minimum load current of 10mA, not 5mA like a more expensive LM117. Then your output voltage will be too high until the total load current (including the current in the 240 ohms resistor and pot) are 10mA. Use 120 ohms to replace the 240 ohms then the unloaded current is 1.25V/120 ohms= 10.4mA and all LM317 devices will work properly.
Since you want a maximum adjusted voltage of 12V then the pot resistance must be reduced to (12V - 1.25V)/10.4mA= 1034 ohms.
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