IC 555 has an internal Flip-Flop and its working determines the output state of the IC. The discharge input of the IC has an NPN transistor with open collector. The On/Off of this transistor also depends on the state of the Flip-Flop. The Flip-Flop is under the control of the lower and upper comparator of the IC which can be independently controlled by external voltage. Here two LDRs are used for controlling the comparators.
Here is an LDR based movement detector for day time use. It is highly useful in shops, banks etc to confirm the entry and exit of persons. It uses two LDRs and the popular timer IC555.
CD4024 is the CMOS Ripple- carry Binary counter / Divider IC used in Control counters, Frequency dividers, Timers and in Time delay circuits.CD 4024 is the 7-stage ripple counter with Master slave Flip-Flops. The counter advances with each negative going pulse in its input. A high going pulse in the reset pin will reset all the counters in zero state. Schmitt trigger action in the input pulse line permits unlimited rise and fall times. All the inputs and outputs are buffered.
Continue reading “CD 4024 Toggle Switch- Design Trick 2”
Design of the popular Timer IC 555 is so interesting and this tiny chip can be exploited in various ways to make different types of circuits. It can be a Monostable, Astable, Bistable, Toggle, Schmitt trigger etc. The Schmitt trigger action is achieved by exploiting the activities of its two internal comparators. Let us make an Automatic Porch light using the Schmitt trigger property of IC 555. It is an ideal circuit to light the premises of home even if the inmates are not there.