The well-known fan cooler, which can be found in household appliances and mainly in computer power supplies, operates at a voltage of 5-12 Volts.But what if the fan needs to be powered from a 220 Volt network? To do this, you can use a step-down mains transformer, but it is bulky and now it is not so cheap.The second option is a switching power supply, this is modern and inexpensive, but the pulser gives interference.The third option is to make a power source for the fan yourself, not heavy and without interference.All this can be done according to the presented scheme.
The capacitor C1 serves to limit the current of the 220V network, I chose 1.5 UF for its capacity and it limits the current at about 110 mA, which is quite enough for a fan.He was given a parallel R2 resistor to discharge it when the device is disconnected from the mains.The resistor R1 performs the function of limiting the charging current of the capacitor C1 during switching on and the function of a fuse.Next, the alternating current enters the diode bridge and is rectified to a pulsating DC.The zener diode serves to stabilize the voltage at about 10 V and the capacitor C2 smooths out current ripples.
The capacitor was applied to a voltage of 275 Volts, this is indicated on the case as 275VAC.This is a capacitor X, it is specially designed for operation in a 220V network.
To find out what current the capacitor limits, I connected a milliammeter to the capacitor and plugged it into the network.The current as seen at 110 mA.
If there is no zener diode, then the constant voltage at the output will not be 10 Volts, but all 207 Volts.The zener diode does not need a current-limiting resistor, the current limits the capacitor.A zener diode with a stabilization voltage of approximately 9-11 volts and a current of more than 200 mA.Instead, you can put another zener diode on the desired current and voltage.
Now everything is assembled and checked.The output of such a power supply will be approximately 10V and the current source can output 100 mA.But it must be borne in mind that the device is not galvanically isolated from the mains, so it is necessary to observe safety precautions, do not touch the details with your hands.
