To automate something or to give alert for some time duration we use Timer circuit, Here is the most useful and efficient 10 Minute Timer Circuit constructed by using famous Timer IC 555 and few easily available components. It is a Monostable Multivibrator which gives always low output and gives HIGH output for particular period of Time (Here calibrated to 10 Minute) when the Trigger signal is applied to it. Just an LED is connected to the output pin along with Two pin Screw terminal, you can connect Buzzer or further actuator to it. Variable Resistor RV1 acts as Timing Resistor(that one is need to be tuned), if you want fixed resistor then calculate the Value by using Monostable Multivibrator Calculator.
About IC 555
Most useful and Most Utilized IC in analog electronics as well as digital electronics is IC 555, Which is Designed by Hans R. Camenzind in 1972, Due to its internal voltage divider setup its been called as 555 (not sure). This IC application expands from basic timers and pulse generators to more complex Oscillators and Pulse Width Modulation (PWM) due to its adaptability and ease of use.
IC 555 Pinout
|Pin Number, Name
|External trigger pulse applied to this pin
|-Ve pulse applied to this pin to disable or reset the time
|5, CONTROL VOLTAGE
|Controls the threshold and trigger levels
|Compares the voltage applied to the terminal with a reference voltage of 2/3 Vcc.
|Open collector output which discharges a capacitor between intervals. toggles the output When 2/3 Vcc.
|Positive supply for IC
This Timer operates in three modes, 1. Astable 2. Monostable 3. Bistable in all modes IC 555 Oscillates pulse depends on the timing elements. For Astable mode continuously Oscillates square pulse at chosen duty cycle. For Monostable only one pulse when ever the trigger input applied. For Bistable timer ic oscillates two stable state output when the trigger input applied.
- Timer IC NE555P
- Pushbutton Switch
- Variable Resistor 1MΩ
- Resistor 10KΩ, 10Ω
- Capacitor 1000μF/16V
- Screw Terminal 2 pin
- battery 9V
Construction & Working
The 555 timer, a versatile integrated circuit, can be configured as a monostable multivibrator, a single shot pulse generator. In this mode, it generates an output pulse in response to the trigger input. When the trigger pulse is applied to the trigger (pin 2) that falls negative(1/3 VCC), the flip-flop of the 555 timer is set, causing the output (pin 3) to go high. The values of the external resistor and capacitor connected are determined as the timing components, the voltage at pin 6 increases until it reaches a threshold level (2/3 VCC), at which time the flip-flop is reset, and the output is low. Time which it takes and reaches this limit is determined by time constants (R – resistance and C – capacitance). Therefore, you can manipulate these external factors to control the stretching of Pulse duration. The monostable mode of the 555 timer finds use in various timing and pulse generation circuits.
To construct the timer IC 555 as a 10 Minute Timer Circuit, the trigger pin should be connected to the ground supply through the push button switch. When the push button switch pressed the trigger pin gets negative supply and triggers the timer IC 555 operation. Timing components VR1 and C1 are connected across the power supply and discharge pin 7, threshold pin 6 are combined and connected to the timing components. The output is connected to the LED through a 10Ω Resistor. Pin 8, 4 connected with 9V battery positive, pin 1 connected with 9V battery negative supply.
By varying the VR1 value we can adjust the output time limit, Calculate the output time limit before implementing the circuit on the field.
T = 1.1*R*C
T = 1.1*546KΩ*1000μF
T = 1.1*546000*0.001
T = 600.6 Seconds
T = 600.6/60 = 10.01 Minute
For 10 Minute Time you have to Set the R (that is VR1) in 546KΩ.
Initially LED will be in ON condition, and Stays in OFF condition When the Push button pressed, After the time duration (10 Minute) LED gets Turn ON. You can use another LED to Indicate the Counting duration (10 Minute) by connecting LED Anode to the Output Pin 3 of Timer IC 555 and LED Cathode to the Negative or Gnd.