- Name: timer_arduino_two
- Title: Micro-controller Countdown Timer
- Description: Countdown Timer: Range 1-99 minutes. Output time (mm:ss) to seven segment display and Audio to Buzzer. Input: Push button to start. Potentiometer used for time select.
- Author: Gavin Lyons
- URL: https://github.com/gavinlyonsrepo/timer_arduino_two
None
Arduino IDE 1.8.5
Eagle 9.3.0
The schematic drawn in Eagle is in documents section.
You will need following parts.
ATmega328p micro-controller as per schematic or alternatively a Arduino uno/nano module.
Resistors: 20 ohms , 220 ohms, 660 ohms, 10K , 500ohms X 7, 1K X 4
Transistors 4 X 2N2222 NPN
One 4 digit seven segment module (SMA420564)
one 50 k potentiometer
one pushbutton
One on/off SPST switches
One piezo buzzer passive
One 16 Mhz crystal
One Lm317 voltage regulator
Capacitors. two x 22pF, three x 100nF , 1uF
The user selects the countdown time (1-99 minutes) with the potentiometer then starts with the pushbutton. Time remaining is displayed on seven segment display. When finished the buzzer is activated and Zero displayed on 4 digit 7-segment display for a few minutes, The unit then shuts off display and buzzer.
LED Array Pin Layout
| Pin Uno | Pin Atmega | 7 Segment pin |
|---|---|---|
| D2 | PD2 | a |
| D3 | PD3 | b |
| D4 | PD4 | c |
| D5 | PD5 | d |
| D6 | PD6 | e |
| D7 | PD7 | f |
| D8 | PB0 | g |
| n/c | n/c | p |
| D10 | PB2 | d4 |
| D11 | PB3 | d3 |
| D12 | PB4 | d2 |
| D13 | PB5 | d1 |
The 4-digit seven segment display (SMA420564 or SM420564) is a common-cathode display.
4 Digit 7 Segment Cathode Red LED Display 0.56" SM420564.
Copyright (C) 2019 Gavin Lyons see LICENSE.md in documentation section for more details