IR Security Alarm Design

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Below is a schematic update suggestion for adding a 555 timer oscillator that drives an alarm buzzer at a 4 kHz tone when the IR beam is interrupted:
Schematic Updates:
  1. Add a 555 Timer in Astable Mode:
    • Add NE555 Timer (if not already in your project).
    • Configure it in astable mode so that when the IR sensor (detecting beam interruption) triggers the circuit, the oscillator continuously outputs a 4 kHz signal.
  2. Select Component Values for a 4 kHz Output:
    • Choose a timing capacitor C = 0.01 µF.
    • Calculate the required resistance values using the formula:
      f=1.44(RA+2RB)Cf = \Large \frac{1.44}{(R_A + 2R_B) C}
      For f = 4000 Hz, a suitable choice is:
      • R_A = 20 k\Omega
      • R_B = 8 k\Omega
        (Since 1.44/((20000+16000)∗0.01×10−6)≈40001.44/((20000+16000)*0.01 \times 10^{-6}) \approx 4000)
  3. Interface with the IR Sensor:
    • Use the output from the IR sensor stage to trigger the 555 timer. For example, when the beam is interrupted (sensor output goes low/high as designed), couple this signal to the control (trigger/reset) input of the NE555 to enable oscillation.
    • You may need to include appropriate biasing or a transistor buffer if the sensor signal level differs from the 555 timer requirements.
  4. Connect the Alarm Buzzer:
    • Connect the output pin (pin 3) of the NE555 to your alarm buzzer.
    • Optionally, include a current-limiting resistor or a driver circuit if the buzzer load requires it.
  5. Additional Decoupling & Supporting Components:
    • Add a 0.1 µF decoupling capacitor between the 555 timer’s VCC and ground.
    • Ensure that all ground connections use the Ground component.
You can use the "Apply changes" button to add these schematic modifications to your project. If you need further assistance with wiring or additional adjustments, let me know!
Add oscillator circuit
Update oscillator wiring
Integrate buzzer driver
Verify component values
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    Chronograph

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    This is a 2 stage IR sensor circuit intended to be used as a ballistic speedometer/chronograph for my Coilgun. I based it off a common design for IR proximity sensors. There are 2 output pins to a microcontroller, and +/-pins for 2 IR receivers, 2 IR emitters, and 2 green LEDs to show when the stage is active. When the beam is broken the voltage on the microcontroller output pins will change, allowing me to code proper coil stage firing timing. The potentiometers are for tuning the sensitivity.

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