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    Now that we know how laser diodes work, it’s time to use one in a project! Karen uses a laser diode and an LDR sensor to create a “trip wire”. When the “wire” is “tripped”, meaning the laser beam is interrupted, lights will flash and an alarm will sound! To create the alarm siren, Karen couples together two 555 timer circuits. The entire project is triggered using a third 555 timer circuit used in bistable mode. And a relay circuit is used to control the motor and LED of the flashing alarm light.

     

    Bill of Material:

     

    Product NameManufacturerQuantityBuy KitBuy Kit
    LM555CN - Timer, Oscillator & Pulse Generator IC, TTL Compatible, Astable, Monostable, 4.5 V to 16 V, DIP-8On Semiconductor3Buy NowBuy Now
    LM317T -1.2V to 37V, 1.5A Adjustable Positive Voltage Regulator in TO-220-3 PackageSTM Electronics1Buy NowBuy Now
    G5V-1-DC5 -Signal Relay, 5 VDC, SPDT, 1 A, G5V-1 Series, Through Hole, Non LatchingOMRON ELECTRONIC COMPONENTS1Buy NowBuy Now
    Ceramic Disc Capacitor, 0.01 µF, 100 V, ± 20%, 5 mmVishay3Buy NowBuy Now
    Electrolytic Capacitor, Miniature, 10 µF, 25 V, 515D Series, ± 20%, Radial Leaded, 5 mmVishay3Buy NowBuy Now
    Through Hole Resistor, 10 ohm, MF25 Series, 250 mW, ± 1%, Axial Leaded, 250 VMulticomp1Buy NowBuy Now
    Through Hole Resistor, 100 ohm, 250 mW, ± 1%, Axial Leaded, 250 VMulticomp1Buy NowBuy Now
    Through Hole Resistor, 1 kohm, 500 mW, ± 1%TT ELECTRONICS / WELWYN1Buy NowBuy Now
    Through Hole Resistor, 10 kohm, 500 mW, ± 5%, Axial Leaded, 350 VMULTICOMP4Buy NowBuy Now
    Through Hole Resistor, 68 kohm, MF25 Series, 250 mW, ± 1%, Axial Leaded, 250 VMulticomp1Buy NowBuy Now
    1N4007 -Standard Recovery Diode, 1 kV, 1 A, Single, 1.5 V, 30 AMULTICOMP PRO2Buy NowBuy Now
    Trimpot, Single Turn, Cermet, Side Adjust, 220 ohm, Through Hole, 1 TurnsBourns1Buy NowBuy Now
    Trimpot, Single Turn, Cermet, Top Adjust, 10 kohm, Through Hole, 1 TurnsBourns1Buy NowBuy Now
    Laser diode - 5mW, 650nm, Red - ModuleAdafruit1Buy NowBuy Now
    2.5 Inch 5.0W 4 Ohm Full Range Speaker, 66mmVisaton1Buy NowBuy Now
    ADVANCED PHOTONIX LDR, Photoresistor, 1 Mohm, 250 mW, 320 VADVANCED PHOTONIX1Buy NowBuy Now
    Rocker Switch, SPDT, On-Off-On, PanelZF ELECTRONICS1Buy NowBuy Now
    Pushbutton Switch, SPST, Off-(On), Round, RedNTE ELECTRONICS1Buy NowBuy Now
    Prototype Board, Phenolic, 30 x 25 grid, 1.6 mm, 94 mm, 71 mmMulticomp1Buy NowBuy Now
    BATTERY HOLDER 4 X AA, 6V, w/ switch, wire leadsOSEPP1Buy NowBuy Now

     

    Additional Parts:

     

    Product Name

    Rotating LED Beacon Light

    Case materials

    Extra Wire

    (4) AA Batteries