The post explains how to make a simple flip flop circuit using IC 4013.

The quick availability of the many CMOS ICs today has made designing of much complicated circuits a child's play, and no doubt the new enthusiasts are enjoying making circuits with these magnificent ICs.One such device is the IC 4013, which is basically a dual D-type flip flop IC, and may be used discretely for implementing the proposed flip flop actions.

In short the IC carries two in built modules which may be easily configured as flip flops just by adding a few external passive components.

IC 4013 Pinout Function

The IC may be understood with the following points.

Each individual flip flop module consists of the following pin outs:

  1. Q and Qdash = Complementary outputs

  2. CLK = Clock input.

  3. Data = Irrelevant pin out, must be either connected to the positive supply line or the negative supply line.

  4. SET and RESET = Complementary pin outs used for setting or resetting the output conditions.

The outputs Q and Qdash switch their logic states alternately in response to the set/reset or the clock pin out inputs.

When a clock frequency is applied at the CLK input, the output Q and Qdash change states alternately as long as the clocks keep repeating.

Similarly the Q and Qdash status can be changed by manually pulsing the set or the reset pins with a positive voltage source.

Normally the set and the reset pin should be connected to the ground when not utilized.

The following circuit diagram shows a simple IC 4013 set up which may be used as a flip flop circuit and applied for the intended needs.

Making a Flip Flop Circuit

Both the flip flop may be utilized if required, however if only one of them is employed, make sure the set/reset/data and clock pins of the other unused section is grounded appropriately.

A practical application flip flop circuit example can be seen below, using the above explained 4013 IC

Mains Failure Backup and Memory for the Flip Flp Circuit

If you are interested to include a mains failure memory and back up facility for the above explained 4013 flip flop design, you can upgrade it with a capacitor backup as shown in the following figure:

As can be seen, a high value capacitor and resistor network is added with the supply terminal of the IC, and also a couple of diodes to ensure that the stored energy inside the capacitor is used for supplying only the IC and not to the other external stages.

Whenever mains AC fails, the 2200uF capacitor steadily and very slowly allows its stored energy to reach the supply pin of the IC keeping the IC's "memory alive" and to make sure that the latch position is remembered by the IC while the mains is unavailable.

As soon as the mains returns, the IC delivers the original latching action on the relay as per the earlier situation, and thus prevents the relays from losing its previous switch ON status during the mains absence.

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