555 timer icClock & Timer Circuit Diagrams

5 to 30 Minute Timer Schematic Circuit Diagram

Description:

To create a switched timer that allows you to select intervals of 5 to 30 minutes incremented in 5-minute steps, you can use a microcontroller-based circuit. Here’s a high-level description of the circuit and functionality:

Components needed:

  1. Microcontroller (e.g., Arduino or similar)
  2. Rotary switch with 6 positions (for selecting 5, 10, 15, 20, 25, or 30 minutes)
  3. Seven-segment display module (for displaying the countdown)
  4. Buzzer (optional for sound notification)
  5. Push-button switch (for starting the timer)
  6. Power supply (Vcc)

Here’s a simplified description of how the circuit works:

Rotary Switch:

  • The rotary switch is used to select the desired time interval. Each position of the switch corresponds to a different time setting: 5, 10, 15, 20, 25, or 30 minutes.

Seven-Segment Display:

  • The seven-segment display will show the countdown timer in minutes and seconds. The microcontroller will control the display to count down from the selected time interval.

Microcontroller:

  • The microcontroller (e.g., Arduino) reads the position of the rotary switch and starts a countdown timer based on the selected time interval.

Push-Button Switch:

  • A push-button switch is used to start the countdown timer. When pressed, it triggers the timer to begin counting down from the selected interval.

Buzzer (Optional):

  • You can include a buzzer for sound notifications when the timer reaches zero.

Here’s a simplified flow of how the circuit operates:

  1. Set the rotary switch to the desired time interval (e.g., 10 minutes).
  2. Press the push-button switch to start the timer.
  3. The microcontroller reads the position of the rotary switch and starts the countdown timer accordingly.
  4. The seven-segment display shows the countdown in minutes and seconds (e.g., 10:00).
  5. The timer counts down in 1-second increments, updating the display accordingly.
  6. When the timer reaches zero, it can activate the optional buzzer for a sound notification.
  7. You can reset the timer by pressing the push-button switch again.

To implement this circuit, you would need to write the appropriate code for your chosen microcontroller (e.g., Arduino) to handle the rotary switch, display, and countdown timer logic. The code would involve reading the rotary switch’s position, updating the display, and managing the countdown timer based on the selected interval.

Circuit diagram

5 to 30 Minute Timer Schematic Circuit Diagram 1

Notes:

Simple to build, simple to make, nothing too complicated here. However you must use the CMOS type 555 timer designated the 7555, a normal 555 timer will not work here due to the resistor values. Also, a low leakage type capacitor must be used for C1, and I would strongly suggest a Tantalum Bead type. Switch 3 adds an extra resistor in series to the timing chain with each rotation, the timing period is defined as:-

Timing = 1.1 C1 x R1

Note that R1 has a value of 8.2M with S3 at position “a” and 49.2M at position “f”. This equates to just short of 300 seconds for each position of S3. C1 and R1 through R6 may be changed for different timing periods. The output current from Pin 3 of the timer, is amplified by Q1 and used to drive a relay.

Parts

Relay 9-volt coil with c/o contact (1)
S1 On/Off (1)
S2 Start (1)
S3 Range (1)
IC1 7555 (1)
B1 9V (1)
C1 33uF CAP (1)
Q1 BC109C NPN (1)
D1 1N4004 DIODE (1)
C2 100n CAP (1)
R6,R5,R4,R3,R2,R1 8.2M RESISTOR (6)
R8 100k RESISTOR (1)
R7 4.7k RESISTOR (1)

Timers can be built using either the 555IC or the 7555IC. However, depending on the IC utilized, there are some changes in the circuit. The 555 IC can’t go rail to rail and is only good for 2Mhz. 7555 IC is the CMOS version of the 555 IC. The output of the 7555 IC is compatible with TTL circuitry. Other than these differences, no matter which IC is used in the circuit, the timing function values stay the same.

A complementary metal-oxide-semiconductor (CMOS) is a small amount of memory on a computer motherboard that stores the Basic Input/Output System (BIOS) settings. The BIOS is the software stored on the memory chip on the motherboard.

CMOS is an innovation used in building integrated circuits. It is used in microcontrollers, static RAM, registers, microchips, and other digital circuits.
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