Voltage fluctuations at potentiometer

Question

I am using the following circuit which receives a DC voltage from a transformed and filter capacitors. I am getting a problem of the voltage changes.

Here without load the potentiometer input coming from the regulator is practically giving:

Without load the voltage I am getting across the load is:

With load the input voltage to the potentiometer becomes:

This input voltage change is not that much but this has resulted in a large change of 2 V in the output which is 9.2 V.

I haven't changed the knob of the potentiometer and I have received an unusual change. What can be the reason. I have used the potentiometer shown below:

This is the complete schematic:

Answer 1

You got some good answers to a very similar question a few days ago, but you appear not to have understood and have not implemented the design changes required.

It would be very helpful if you would draw a schematic using CircuitLab or LTspice, so you can run simulations and see the effects of various component changes and design modifications. If you are making an actual breadboard, there may be some problems due to grounding and poor connections, especially if you are running more than a couple amps.

Here is a simple implementation of a variable 0-12 V power supply, set to 6 V, showing raw DC voltages for loads of 10, 100, and 1k, and control and output voltages for 10 and 1k loads.

^{simulate this circuit – Schematic created using CircuitLab}

(edit) Here is a way to achieve nearly perfect correlation between a control signal and output:

^{simulate this circuit}