DIAC CONTROLLED FLASHER
101％ working project hello friends today I am gonna telling you about some easy and valuable electronics projects for school and college practical
This simple flasher finds various industrial applications as a high - voltage indicator or machine - ' on' indicator . It flashes once every second to give a warning indication . It is simple to design and can be wired lead - to - lead without using PCB. It is directly powered from 220V AC and can be enclosed in the mains box.
Mains 230V AC is rectified by Di. which reduces it to a safer level through 33 kilo-ohm resistor R1 . Capacitor C1 ( 470pF , 100V ) charges through diode D1 and resistor R1`which reduces the flow of current to the diac and hence the triac remains non - conducting.
After capacitor C1 is fully charged the voltage across the diac rises and it conducts . This provides gate current to the triac through R2 . The triac fires and completes the circuit of the lamp and it glows.
Fig1; circuit diagram
The triac ( BT136 ) comprises two silicon - controlled rectifiers ( SCRs ) connected in the reverse parallel configuration sharing the same gate circuit . When the triac fires , both the SCR portions conduct . The gate of the triac is quite complex and it can be triggered by DC , rectified AC , AC or pulse sources like neon lamps or switching diodes like diacs.
Since the circuit uses 220V AC , all the points are at mains lethal potential . Adequate spacing and use of lead sleeving is required as saftey measures while assembling the circuit . Do not enclose the circuit in a metallic cabinet unless it is made fully shockproof Also , do not solder or desolder the components when the circuit is powered .
