555 ics hysteresis for dark activated

Posted on Feb 4, 2014

This is a circuit that can be used for dark activated means the relay will be activated when thelight intensity fall below a certain threshold. Without hysteresis, the relay will be activated and deactivated if the sensed brightness fall under or rise above a single point of darkness level. With hysteresis, the darkness level for activating and de

555 ics hysteresis for dark activated
Click here to download the full size of the above Circuit.

activating the relay will be different, and this solve the relay oscillation problem when the light intensity is swinging up and down around a single point of no hysteresis activation level. Here`s the figure of the circuit; We can employ the hysteresis of a 555 IC to improve the sensingof a drop in light, since the internal 555 circuit has 1/3 and 2/3supply voltage thresholds. We have to use a LDR or CDS cell with out 2 to 8 k resistance at desired light level. At the dark, the resistance of the LDR will rise and activate the relay if the voltage at pin 2 reach 2/3 of supply voltage (8V). After the relay is activated, more light is needed to make the LDR decrease its resistance until the voltage at pin 2 falls below 1/3supply voltage (4V).

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Clock/Calendar/Alarm with ATtiny12
    AVR LED RF Field Strength
    Monostable to bistable relay with momentary switch
    Vhf-Uhf Preamp Circuit
    switching power supply 2
    Voice Bandwidth Filter