Current control circuit for a power supply was studied and designed. The circuit will be used with a direct current power supply to generate constant current for resistive magnet of NMR machine. The designed circuit detect a voltage across a sense resistor connected in series to the power supply. The voltage is then converted to a current value to control the cerrent through a power transistor. The AVR microcontroller number Atmega32 was used in this project. This microcontroller has analog input for detecting a power supply voltage.