1 to 12 volts Power Supply with Led Indicator
This is a 1.2 - 12 V, max 1A power supply with a low voltage indicator LED. The indicator part includes three diodes and one LED. For example you are charging a battery, you can observe the charge status at that moment. Another advantage of this circuit, when the drawn current exceeds 1A (practically 0.85A), the current protector in LM317 intervenes and LED indicator warns you about the very low output voltage.
Be careful while choosing the transformer. Most of the products are specified as 10VA but their outputs are not as said.
Another good property of this circuit is the mains noise does not pass to the DC part.