Flashing glowing indicator light switch circuit

Figure 2 shows a light switch circuit with a flashing light indicator . When s is closed, the light E lights normally and flashes
to indicate that the electric hoof loses power and does not work. After opening s. The 220V alternating current is rectified by the bulb E and the diode VD1, and R
reduces the voltage and limits the current to charge the capacitor c. This circuit uses the negative resistance of the bidirectional trigger diode VDH and
the charging and discharging principle of the capacitor C to form a relaxation oscillator. Therefore, the light-emitting tubes I and ED will flash and glow, which is very eye-catching at night
, making it easy for people to find the switch. Location. If s is turned off and the LED glows slightly, either the filament of the bulb E
is burned out or the power grid is out of power.
    VDH can use bidirectional trigger diodes with a transition voltage in the range of 20-40V, such as 2CTSIA, DB3
type, etc. I.ED uses high-brightness red light-emitting diodes.