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Digital Controlled Linear Power Supply

In myteenage years, about 40 years ago, I created a dual linear power supply. I got the schematic diagram from a magazine called ‘Elektuur’, nowadays called ‘Elektor’ in The Netherlands. This power supply used one potentiometer for the voltage adjustment and one for the current adjustment. After many years these potentiometers did not function correctly anymore which made it difficult to get a stable output voltage. This power supply is shown in the picture.

In the mean time I picked up embedded software development as part of my hobby, using the PIC microcontroller and the JAL programming language. Since I still want to use my power supply – yes you can buy cheaper switch mode variants nowadays – I got the idea to replace the old potentiometers by a digital version and so a new PIC project was born.

For adjusting the voltage of the power supply I am using a PIC 16F1823 microcontroller that uses 6 push buttons as follows:

One push button for switching the output voltage on or off without the need to switch the power supply on or off completely
One push button to increase the output voltage and another one push button to decrease the output voltage
Three push buttons to be used as preset. After having set a certain output voltage, that exact voltage can be stored and retrieved using these preset push buttons
The power supply is capable of outputting a voltage between 2.4 Volt and 18 Volt with a maximum current of 2 Ampere.”

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