Laser Detonation Device


Group Members
Frank Graffagnino
Michael DeRouen
Jeremy Moreau


This project was an assignment from my Electronics II class (EECE 353).






Abstract

This device is basically a laser transmitter to be used as a detonation trigger. Since detonation requires extreme safety, this trigger was made to operate at a certain frequency. When this specific signal is superimposed on the laser, the explosive is detonated. This creates extra stability due to the fact that ambient light cannot generate a detonation tone and the explosive detonates only when it is intended to. This detonation was simulated with a light bulb up until the final run.





Design

The design basically consists of three circuits that function as one: the transmitter circuit, the reception circuit, and the frequency detection circuit.


The Transmitter Circuit

The transmitter circuit is nothing more than a very low power laser pointer with a transformer in series with its negative power supply. This allows the signal to be super-imposed on top of the laser intensity.






The Reception Circuit

A phototransistor and an operational amplifier are basically all that is used in the reception of the laser. The phototransistor works in active mode with the light intensity acting as the base of the transistor. This single stage amplifier drives the input to the 741 op-amp, which amplifies the signal to an amplitude that is detectable by the next stage.





The Frequency Detection Circuit

A phase lock loop circuit was implemented to detect a frequency of 46 kHz. The output signal was active high until the frequency is detected on the output line. After a small delay (0.25 - 0.5 second), the phase lock loop makes the output go low using TTL logic. This output signal is placed on one side of the relay coil to cause it to switch on when the frequency is detected. Unfortunately, we do not have a schematic of this portion but we do have a picture.





Implementation

The implementation of our design took course primarily over three days. The first day consisted of building the circuits and testing them in the lab. We then moved it out of the window of the lab to test at a far distance of approximately 100 feet.

The second day of implementation mainly evolved around the testing of constructed explosives to be used in the final run. This will not be covered here nor will any pictures or any construction information be given about the explosives used.

The third and final day of implementation required us to move our circuit to the detonation site. Here we tested and filmed the final results of our project.



Implementation Day 1

First we moved the receiver outside and ran power to it with extension cords:



Then we began to test. We ran into some problems with the frequency but found out that the phase lock loop frequency we had designed for had shifted due to temperature change. This was easily remedied and we were able to turn the light on and off.



Here is picture of the laser beam through some chalk dust:





Implementation Day 3

The BIG day! First we set up our circuits in an open area.









Here is a picture of the operating station (the transmitter circuit a safe distance away):



Detonation was also simulated here with the light bulb before any other device was plugged up! The following are still frames from the video:

It seems we have a little visitor (DISCLAIMER: No bunnies were hurt in the making of this project)...



These pictures are of the final run. The first image shows the frequency generator on 46 kHz which means that this image is just prior to actual detonation.



Now onto the explosion!!!
































Conclusion

As one can see, the project and detonation were a complete success due to careful planning and testing ahead of time. Extreme caution was taken and nothing was rushed. This led to a project that was not only fun, and exciting, but an extreme learning experience.


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