Monday, February 6, 2012

How to Make a LED Chaser cum Blinker Circuit Using IC 4017


  The presented circuit was requested by Mr.Joe, one of the keen followers of this blog. The circuit initially was intended to be used for generating LED strobe light effects and was asked to be modified such that it could be used as an LED sequencer as well as a blinker. The change over would be implemented via a toggle switch.

The circuit diagram may be understood with the following points:

The IC 4017 is not new to us and we all know how versatile and competent this device is. Basically the IC a Johnson’s decade counter/divide by 10 IC, fundamentally used in applications where sequencing positive output signals are required or desired.

 The sequencing or the orderly shifting of the outputs take place in response to a clock pulse that needs to be applied at the clock input pin #14 of the IC.

With every rising positive edge of the clock input, the IC responds and pushes its output’s positive from the existing pin out to the next pin out in the order.

Here a couple of NOT gates are used as a oscillator for providing the above clock pulses to the IC 4017. VR1 may be adjuted for determining or fixing the speed of the sequencing.

The outputs of the IC are connected to an array of LEDs in a specific order which makes the LEDs look like as if they are running or chasing during the operations.

If the circuit would be required only to produce the chasing effect, the diodes would not be required, however as per the present ask the diodes become important and allows the circuit to be used as a blinker also, depending upon the position of the switch S1.

When the switch S1 is positioned at A, the circuit behaves like a light chaser and produces the normal chasing effect over the LEDs which start illuminating in sequence from top to the bottom, repeating the operations as long as the circuit remains powered.

As soon as S1 is flicked toward B, the clock signals from the oscillator are shifted into the input of the transistor T1, which instantly stats to pulsate all the LEDs together in response to the received clocks from N1/N2 configuration.

Thus as per the requirement we have successfully modified an ordinary light chaser circuit with an additional feature through which the circuit now is also able to function as a LED flasher.

Do not forget to connect the inputs of the remaining unused gates from the IC 4049 either to the positive or the negative of the supply. The supply pins of the IC 4049 also need to be connected to the relevant supply rails of the circuit, kindly refer to the datasheet of the IC.

Tf all the ten outputs of the IC 4017 are required to be integrated with LED sequencing, just connect pin #15 of the IC to ground and use the left over outputs of the IC for the required sequencing of the LEDs in the order of: 3,2,4,7,10,1,5,6,9,11


Parts List

The fooliwng parts will be needed for making this LED light chaser cum flaher circuit:

R1, R2, R3 = 1K,
R4 = 100k
VR1 = 100K linear pot.
All LED resistors are = 470 Ohms,
All diodes are = 1N4148,
All LEDs = RED, 5mm or as per choice,
T1 = 2N2907, or 8550 or 187,
C1 = 10uF/25V
C2 = 0.1uF,
IC1 = 4017,
N1, N2 = IC4049

18 comments:

  1. You said a clock pulse needed to be applied to input 14. Would that just be applying power to the chip or something different.

    ReplyDelete
    Replies
    1. Clock pulse means a frequency or generation of alternate positive and negative pulses.
      The function is done by the gates N1, N2, the output from N2 provides the required clock pulses to pin14 of the IC 4017 when the switch is connected to point A.

      Regards.

      Delete
  2. im not seeing point A on the schematic and not sure where it is.

    ReplyDelete
  3. Good day sir swagatam. pls i want to understand something about this interesting circuit. Is it thesame set of LED that chase that also blink or we need to connect a different set of LEDs to the transistor for the blinking operation? Pls clear me on this. Thanks as i await your reply

    ReplyDelete
    Replies
    1. Hi Tombari,

      The circuit can be made to work both ways.
      If you connect separate LEDs to the lower diodes, they will blink while the upper LEDs will chase depending upon the position of S1.
      If you connect the lower diodes to the black points of the upper diodes, the connected LEDs can be made to chase or blink depending upon the position of the switchS1

      Regards.

      Delete
  4. Thank you for your response. Please i will like to propose a modified circuit in which if we have two set of LEDs then the upper ones should be chasing while the lower ones are flashing simultaneously. A second modified circuit should be such that the switching action from chasing to flashing is done automatically after a set time either by a relay or other timing sub unit. Thanks. Electronics is the best field!

    ReplyDelete
    Replies
    1. Great suggestion Tombari, if I get time I'll surely update the idea here.

      Thanks and Regards.

      Delete
    2. Hello Swagatam,
      I am in need of assistance. I want to build a small LED array of 5-6 different colored LEDs that light one at a time for a period of 3-5 seconds in a loop. The LED sequencers I see everywhere light too fast. I want them to cycle through the 5-6 LEDs at a slower rate and stay illuminated for 3-5 seconds before moving to the next blub.
      Can you assist me with this?

      Thanks,
      Steve

      Delete
    3. Hello Steve,

      You just need to increase the value of the oscillator capacitor C1 for the desired effects. Increase the value appropriately until you get the desired effects.

      Delete
  5. Is it possible to make LED sequencer circuit using any BGA or any other smaller IC than 555?

    reply

    ReplyDelete
    Replies
    1. LED sequencer or LED chaser is possible only with ICs like 4017 etc, I have no idea about other options.

      Delete
  6. Is it possible to make a circuit which will be a blinker and a sequencer? As in, the first LED will be turned ON for 10 milliseconds and then turned OFF for 2 seconds, followed by the next LED doing the same?

    ReplyDelete
    Replies
    1. the above circuit will work in that way only, T1 stage and all the diodes will not be required in that case.

      Delete
  7. Please indicate c1 and vr1 terminal signs indetail.

    ReplyDelete
    Replies
    1. c1 is nonpolar, vr1 center and one outer lead joins with the ground and the other free end to R1.

      Delete

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Readers are advised to proceed with the construction of the presented circuits only after understanding the concepts from the core. Not adhering to this can lead to failures and frustrations.