Laser Beams and 555

A laser trip wire that activates a camera. An ambient light sensor from Vishay, the TEMT6000, operates as an NPN transistor connected to a 555 timer in bistable mode. The output is directed to a logic inverter for quick visual status, and then routed to another 555 timer configured in monostable mode. The output from this 555 timer can be utilized to actuate various devices, such as an electric squirt gun, sirens, Nerf guns, etc. In this example, the camera is set to continuous fire mode, as the output remains active for several seconds. This setup could be employed to capture images of a burglar attempting to steal the camera or for more practical purposes, such as taking pictures at the end of a race.

The laser trip wire system integrates a laser emitter and a photodetector, which together create an invisible beam. When the beam is interrupted, the photodetector triggers the ambient light sensor (TEMT6000). This sensor is sensitive to changes in light intensity, effectively acting as an NPN transistor switch. Upon detecting the interruption of the laser beam, the sensor outputs a signal that is fed into the first 555 timer configured in bistable mode. This configuration allows the circuit to switch between two stable states, enabling the system to remain in one state until the laser beam is restored.

The output from the bistable 555 timer is then sent to a logic inverter, which provides a quick visual indication of the system's status. This could be implemented with an LED that lights up when the beam is broken, providing immediate feedback to the user. Following this, the signal is sent to a second 555 timer set up in monostable mode. The monostable configuration generates a single output pulse of a defined duration when triggered. This pulse can be programmed to last several seconds, allowing ample time for the camera to capture images.

The versatility of the output from the monostable timer allows it to control various devices, enabling the system to be expanded beyond just a camera. The activation of devices like electric squirt guns, sirens, or toy guns adds an element of surprise or deterrence, making the system suitable for security applications. The continuous fire mode of the camera ensures that multiple images can be captured in succession, which is particularly useful in scenarios such as monitoring for intruders or documenting events like races. This comprehensive setup exemplifies an innovative use of basic electronic components to create a functional and effective security system.A laser trip wire that actuates a camera. An ambient light sensor by Vishay, the TEMT6000 [ datasheet ] from Sparkfun Electronics, acts as an NPN transistor attached to a 555 in BiStable mode. The output is sent to a logicinverter for quick visual status, then off to another 555in Monostable configuration.

The output from that 555 canbe used to actuate any number of devices (Electric squirt gun, Sirens, Nerf guns, etc. ), but in this exampleI have my camera set up in continious fire mode, as the output stayes on for several seconds. This could be used forcatching a burgler (who probably wants to steal my camera), or more usefull items such as taking pictures at the end of a race.

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