My workbench has many broken devices and most of them will be used as the part for making the electronic projects. One day I looked at the broken radio, I found there's an AC line cord with socket and a transformer. Actually I like the way they used AC socket with the AC cord. I thought why don't make a simple DC supply from these parts. Most of the DC adapters provide only DC output. But not AC output, some of the uC circuit need a +5V for digital circuit, some need an AC line voltage for timing synchronization, digitizing sine wave, and some need unregulated for relay driving. So I designed above circuit for lab usage. The circuit is a linear regulator providing galvanic isolation from main line through the use of isolation transformer. Quite safe for experimenting with AC voltage. Below pictures show the example of input/output terminal connections, labeling and components placement in the box. The circuit can be built using universal PCB. The output terminal is for big load connection so this makes it quite strong and good electrical contact to the load being used.
Part List for the Student DC Supply
U1- 7805 three terminal +5V Voltage regulator
D1- DB102 bridge diode
D2- 1N4001 silicon rectifier diode
C1- 1000uF, 25V, electrolytic capacitor
C2- 10uF, 16V, electrolytic capacitor
C3- 0.1uF disc ceramic capacitor
T1- transformer 220V primary 7.5V secondary 500mA
*all of above pictures including
circuit diagram are captured by using a low cost (3,300 Baht) scanner,
Acer S2W 3300U (Scan-to-Web), not an expensive digital camera. I
was surprised! the result output files are pretty impressive.
