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Built-in project · no microcontroller

Decade chaser

A 555 astable clocks a CD4017 decade counter and ten LEDs take turns to light, with no microcontroller. There is no microcontroller in it: the simulator solves the 15 parts as a circuit, so it runs the moment you press Run, and nothing needs compiling.

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Decade chaserlive0.000 s 0.00x
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How it works

There is no microcontroller in this one, so nothing is compiled: the simulator solves the circuit itself. The file in the editor is the notes that come with it.

sketch.ino
// A 4017 LED chaser: a 555 clock and a decade counter. No code.
//
// The 555 on the left is an astable: the capacitor charges through RA and RB
// and discharges through RB, over and over, and OUT is a square wave at
//
//   f  =  1.44 / ((RA + 2 x RB) x C)  =  1.44 / (76k x 4.7 uF)  =  about 4 Hz
//
// Every rising edge on the 4017's CLK moves the one high output along: Q0,
// Q1, Q2 ... Q9 and round again. The outputs are not in order round the chip
// (pin 1 is Q5, pin 3 is Q0), which is why the wires to the LEDs cross.
//
// The LEDs have no resistors. A CD4017 output can only push a few milliamps
// (it is a 500 ohm switch at 5 V), so it limits the current itself. Change
// the capacitor in the properties panel to speed the chase up or slow it down.
//
// Things to try: wire Q5 to RST instead of grounding RST, and it counts to
// five and starts again.

Parts list

17 parts, plus the jumper wires. Every one is in the editor's parts bin.

How it is wired

15 connections, pin by pin, read from the circuit itself. Each line is one set of pins joined together, by a jumper wire or a breadboard strip.

  • 5 V: NE555 timer pin RESET; NE555 timer pin VCC; Resistor, 10k Ω pin 1; CD4017 decade counter pin VDD
  • Ground: NE555 timer pin GND; Capacitor, 4.7 µF pin 2; CD4017 decade counter pin VSS; CD4017 decade counter pin INH; CD4017 decade counter pin RST; LED, green pin C; LED, red (1) pin C; LED, red (2) pin C; LED, red (3) pin C; LED, red (4) pin C; LED, red (5) pin C; LED, red (6) pin C; LED, red (7) pin C; LED, red (8) pin C; LED, red (9) pin C
  • NE555 timer pin TRIG; NE555 timer pin THR; Resistor, 33k Ω pin 2; Capacitor, 4.7 µF pin 1
  • NE555 timer pin OUT; CD4017 decade counter pin CLK
  • NE555 timer pin DIS; Resistor, 10k Ω pin 2; Resistor, 33k Ω pin 1
  • CD4017 decade counter pin Q5; LED, red (5) pin A
  • CD4017 decade counter pin Q1; LED, red (1) pin A
  • CD4017 decade counter pin Q0; LED, green pin A
  • CD4017 decade counter pin Q2; LED, red (2) pin A
  • CD4017 decade counter pin Q6; LED, red (6) pin A
  • CD4017 decade counter pin Q7; LED, red (7) pin A
  • CD4017 decade counter pin Q3; LED, red (3) pin A
  • CD4017 decade counter pin Q8; LED, red (8) pin A
  • CD4017 decade counter pin Q4; LED, red (4) pin A
  • CD4017 decade counter pin Q9; LED, red (9) pin A

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