Tuesday, December 04, 2018

LED Running lights CD4017

This Demo shows LM555 running a CD4017 Counter to drive Ten Leds sequentially. Red Button Powers LED Running Lights, 555 Clock is counted by CD4017. Adjust R2, See ToolTips.

Screenshot of gadget

LED Running lights CD4017

This is a Gadget Tutorial for this Article LED Running lights CD4017.

Press the Red button below to turn on the circuit press it again to turn off, i have put a new battery and did the wiring for you. The Red LED will flash according to the state of the 555 output at pin 3. The decade counter-divider CD4017 has 10 outputs, for every low to high transition, rising edge, the counter advances one LED. After going one full circle the the first LED lights again and it goes on.....


You can vary the value of R2 using the controls below to make LEDs run fast or slow. The frequency of oscillation of astable 555 is given as f = 1.44 / ((R4 + 2 * (R2 + R3)) * C3).

The 10 outputs have 10 green LEDs. The current thru the LED is limited by R1, the current can be calculated like this (9V - 1.6V) / 1K = 7.4mA this is within 20mA which is the danger limit of the CMOS output. You want it to be bright use transistors for every output.

LED Running lights

The cap C1 is a filter and C2 is to prevent noise at pin 5 influencing the output as it is a control voltage point.

You can cascade or chain many more counters with the CO or carry out pin 12 of 4017. The pin 15 reset is kept at low for counting, on high it will reset the counter but is not used in this circuit.(More logic than just cascade if you want just one LED to run say in a chain of 100 LEDs, but that may not be decorative)

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