Three-minute-timer
When S1 is off, C1 charges to within 0.5 V of the battery voltage through diode D1 and resistor R4. When S1 is closed, the anode of the PUT rises to the positive supply voltage. The PUT does not conduct because the battery voltage appears in series with the charge stored on C1, which raises the gate of the PUT to a level positive with respect to the anode. The timer relies on the discharge of capacitor C1 through resistors R1, R2, R3, and R4. Once C1 is at zero volts, the PUT will turn on battery voltage to the Sonalert and cause it to sound.
The described circuit operates as a timer using a Programmable Unijunction Transistor (PUT) and a capacitor (C1) to control the activation of an alerting device, specifically a Sonalert. Initially, when switch S1 is open, capacitor C1 charges through diode D1 and resistor R4, allowing it to reach a voltage close to the battery voltage, specifically within 0.5 volts. This charging phase is critical for establishing the baseline voltage needed for the subsequent operation of the PUT.
When switch S1 is closed, the voltage at the anode of the PUT increases to match the positive supply voltage. However, the PUT remains off at this stage due to the voltage drop across C1, which acts to raise the gate voltage of the PUT above the level present at the anode. This condition prevents the PUT from conducting, allowing the circuit to remain in a non-active state.
The timing mechanism is realized through the discharge of capacitor C1, which occurs via the resistors R1, R2, R3, and R4. As C1 discharges, its voltage decreases until it reaches zero volts. At this point, the charge level in C1 no longer supports the gating condition of the PUT, and it turns on, allowing the battery voltage to flow to the Sonalert. This activation results in the Sonalert producing an audible sound, signaling the end of the timing period.
The design emphasizes the interaction between the passive components (capacitor and resistors) and the active component (PUT), showcasing a simple yet effective timing mechanism suitable for various alerting applications. The circuit's performance can be influenced by the values of the resistors and the capacitance of C1, allowing for adjustments to the timing characteristics as needed.When Sl is off, Cl charges to within 0.5 V of the battery voltage through diode Dl and resistor R4. When Sl is closed, tbe anode of tbe PUT rises to the positive supply voltage. The PUT does not conduct, because battery voltage appears in series with tbe charge stored on Cl, which raises the gate of the PUT to a level positive with respect to the anode. The timer relies on the discharge of capacitor Cl through resistors Rl, R2, R3,and R4. Once Cl is at zero volts, the PUT will turn on battery voltage to the Sonalert and cause it to sound.
The described circuit operates as a timer using a Programmable Unijunction Transistor (PUT) and a capacitor (C1) to control the activation of an alerting device, specifically a Sonalert. Initially, when switch S1 is open, capacitor C1 charges through diode D1 and resistor R4, allowing it to reach a voltage close to the battery voltage, specifically within 0.5 volts. This charging phase is critical for establishing the baseline voltage needed for the subsequent operation of the PUT.
When switch S1 is closed, the voltage at the anode of the PUT increases to match the positive supply voltage. However, the PUT remains off at this stage due to the voltage drop across C1, which acts to raise the gate voltage of the PUT above the level present at the anode. This condition prevents the PUT from conducting, allowing the circuit to remain in a non-active state.
The timing mechanism is realized through the discharge of capacitor C1, which occurs via the resistors R1, R2, R3, and R4. As C1 discharges, its voltage decreases until it reaches zero volts. At this point, the charge level in C1 no longer supports the gating condition of the PUT, and it turns on, allowing the battery voltage to flow to the Sonalert. This activation results in the Sonalert producing an audible sound, signaling the end of the timing period.
The design emphasizes the interaction between the passive components (capacitor and resistors) and the active component (PUT), showcasing a simple yet effective timing mechanism suitable for various alerting applications. The circuit's performance can be influenced by the values of the resistors and the capacitance of C1, allowing for adjustments to the timing characteristics as needed.When Sl is off, Cl charges to within 0.5 V of the battery voltage through diode Dl and resistor R4. When Sl is closed, tbe anode of tbe PUT rises to the positive supply voltage. The PUT does not conduct, because battery voltage appears in series with tbe charge stored on Cl, which raises the gate of the PUT to a level positive with respect to the anode. The timer relies on the discharge of capacitor Cl through resistors Rl, R2, R3,and R4. Once Cl is at zero volts, the PUT will turn on battery voltage to the Sonalert and cause it to sound.