This power supply can be used as battery eliminator to power small transistorized devices such as radios, calculator, clocks, etc. In the transformerless source, the capacitive reactance of C1 is used to reduce the voltage to a suitable value, regulated by zener DZ. This zener can be 6, 9 or 12 V, depending on the desired voltage and with a dissipation of 1 W.
As shown in the diagram of Figure 1, rectification is done by D1 and C2 filtering, which should be as large as possible. For normal applications, 1000 uF will be sufficient and the working voltage of at least 12 V.
The capacitor C1 must not be electrolytic but rather depolarized, such as polyester, with a working voltage of at least 400 V.
The terminal strip mounting is shown in figure 2.
It is important to remember that the non-existence of a transformer causes the source to have a direct connection to the power network, so there is no isolation. Thus, there is a risk of shock in a contact with the supplied circuit. The maximum current of the source is of the order of 50 mA.
Material list
DZ- 6, 9 or 12 V x 1 W zener diode
D1- 1N4002 or equivalent silicon diode
C1- 330 nF or 470 nF x 400 V or more-polyester capacitor
C2- 1 000 uF x 12 V-electrolytic capacitor
R1- 100 ohms x ½ W - resistor - brown, black, brown
Miscellaneous: terminal strip, power cable, wires, solder, etc.
