© Bill Bowden, 1999
I found this schematic on the Internet, designed by Bill Bowden.
Parts List
- 1 × 555 IC
- 1 × 4017 IC
- 8 × 1N914 diodes
- 4 × 2N3904 transistors
- 1 × 10KΩ resistor
- 1 × 47KΩ resistor
- 2 × 180Ω resistors
- 1 × 10µF capacitor
- 2 × green 3mm LEDs
- 2 × yellow 3mm LEDs
- 2 × red 3mm LEDs
Parts Discussion
555 IC
An excellent tutorial on the 555 timer IC was written by Tony van Roon and is recommended reading if you want to understand this great little chip.
| Pin | Name | Discussion |
|---|---|---|
| 1 | GND | Ground |
| 2 | TR | Trigger |
| 3 | Q | Output |
| 4 | RST | (not used, tied to VCC) |
| 5 | CV | (not used) |
| 6 | TH | The threshold at which the interval ends. |
| 7 | DIS | Connected to a capacitor whose discharge time will influence the timing interval. |
| 8 | VCC | The positive supply voltage. |
4017 IC
The 4017 IC is a decade counter (0 – 9), incrementing everytime it receives an input signal on CLK.
| Pin | Name | Discussion |
|---|---|---|
| 1 | Q5 | The 6th sequential output. |
| 2 | Q1 | The 2nd sequential output. |
| 3 | Q0 | The 1st sequential output. |
| 4 | Q2 | The 3rd sequential output. |
| 5 | Q6 | The 7th sequential output. |
| 6 | Q7 | The 8th sequential output. |
| 7 | Q3 | The 4th sequential output. |
| 8 | GND | Ground |
| 9 | Q8 | The 9th sequential output. |
| 10 | Q4 | The 5th sequential output. |
| 11 | Q9 | The 10th sequential output. |
| 12 | CO | (not used) |
| 13 | LE | (not used, tied to ground) |
| 14 | CLK | Clock input |
| 15 | RST | (not used, tied to ground) |
| 16 | VCC | The positive supply voltage. |