The circuit is using two different voltage regulator ICs. First is a LM7809 IC, it is a fixed voltage regulator IC, it is use to convert the output of 14V plug pack to 9V for arduino board. The next IC is a LM317T that is an adjustable positive voltage regulator IC, it is used to convert the output of plug pack to any voltage between 1.2V to 12V. A suitable heatsink is must for both ICs.
An arduino is a 5V device therefore it cannot drive projects which require more than 5V DC, and normally you have to use external power supplies. This power supply for arduino projects can be used to supply the power to arduino & its projects. The supply is adjustable and it can be adjusted
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