DIY Laser Trip Wire Alarm
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 Name | Manufacturer | Quantity | Buy KitBuy Kit |
|---|---|---|---|
| LM555CN - Timer, Oscillator & Pulse Generator IC, TTL Compatible, Astable, Monostable, 4.5 V to 16 V, DIP-8 | On Semiconductor | 3 | Buy NowBuy Now |
| LM317T -1.2V to 37V, 1.5A Adjustable Positive Voltage Regulator in TO-220-3 Package | STM Electronics | 1 | Buy NowBuy Now |
| G5V-1-DC5 -Signal Relay, 5 VDC, SPDT, 1 A, G5V-1 Series, Through Hole, Non Latching | OMRON ELECTRONIC COMPONENTS | 1 | Buy NowBuy Now |
| Ceramic Disc Capacitor, 0.01 µF, 100 V, ± 20%, 5 mm | Vishay | 3 | Buy NowBuy Now |
| Electrolytic Capacitor, Miniature, 10 µF, 25 V, 515D Series, ± 20%, Radial Leaded, 5 mm | Vishay | 3 | Buy NowBuy Now |
| Through Hole Resistor, 10 ohm, MF25 Series, 250 mW, ± 1%, Axial Leaded, 250 V | Multicomp | 1 | Buy NowBuy Now |
| Through Hole Resistor, 100 ohm, 250 mW, ± 1%, Axial Leaded, 250 V | Multicomp | 1 | Buy NowBuy Now |
| Through Hole Resistor, 1 kohm, 500 mW, ± 1% | TT ELECTRONICS / WELWYN | 1 | Buy NowBuy Now |
| Through Hole Resistor, 10 kohm, 500 mW, ± 5%, Axial Leaded, 350 V | MULTICOMP | 4 | Buy NowBuy Now |
| Through Hole Resistor, 68 kohm, MF25 Series, 250 mW, ± 1%, Axial Leaded, 250 V | Multicomp | 1 | Buy NowBuy Now |
| 1N4007 -Standard Recovery Diode, 1 kV, 1 A, Single, 1.5 V, 30 A | MULTICOMP PRO | 2 | Buy NowBuy Now |
| Trimpot, Single Turn, Cermet, Side Adjust, 220 ohm, Through Hole, 1 Turns | Bourns | 1 | Buy NowBuy Now |
| Trimpot, Single Turn, Cermet, Top Adjust, 10 kohm, Through Hole, 1 Turns | Bourns | 1 | Buy NowBuy Now |
| Laser diode - 5mW, 650nm, Red - Module | Adafruit | 1 | Buy NowBuy Now |
| 2.5 Inch 5.0W 4 Ohm Full Range Speaker, 66mm | Visaton | 1 | Buy NowBuy Now |
| ADVANCED PHOTONIX LDR, Photoresistor, 1 Mohm, 250 mW, 320 V | ADVANCED PHOTONIX | 1 | Buy NowBuy Now |
| Rocker Switch, SPDT, On-Off-On, Panel | ZF ELECTRONICS | 1 | Buy NowBuy Now |
| Pushbutton Switch, SPST, Off-(On), Round, Red | NTE ELECTRONICS | 1 | Buy NowBuy Now |
| Prototype Board, Phenolic, 30 x 25 grid, 1.6 mm, 94 mm, 71 mm | Multicomp | 1 | Buy NowBuy Now |
| BATTERY HOLDER 4 X AA, 6V, w/ switch, wire leads | OSEPP | 1 | Buy NowBuy Now |
Additional Parts:
| Product Name |
|---|
Rotating LED Beacon Light |
Case materials |
Extra Wire |
(4) AA Batteries |