High Speed Photography with electromagnetic gun
Section 1: My thought begins with building an electromagnetic gun
The thought I had to make an electromagnetic gun is generated from my engineering intuition. I once said in the classroom that I wanted to make an amplifier, a voice amplifier. This was because I want to finish this course with a design with the procedure from circuit design to the actual physical components design. I used to design an amplifier and I used to want to use this chance to make it true. However, due to it will be just an amplifier (not fun), I abandaned that idea. After a Google search in my mind about how to use my knowledge to start a circuit design, I came up with the idea about the Electromagnetic Gun.
The electromagnetic gun is made by many circuit components: transistors, diodes, capacitors, ziodes, resistors, coils and of course the power supply. I found many versions for circuit design of electromagnetic guns, and I ended up with using the circuit diagram below following the Youtube video.
Version 1: Prototype
Everything starts with prototype that tries out the accessibility of the circuit design. I started by getting all the required materials in the circuit and built it. Every component I got was from Taobao and I followed exactly the same procedure on the Youtube video: here it comes the prototype.
I powered it up with four 5V batteries which can help me charge the capacitor really fast. The digital screen is basiclly a voltage meter which shows how much voltage is charged across the capacitor. Two bottoms are designed as the charging botton (yellow one) and the other was the firing botton (red one). All the devices are put in a bubble box for safety reasons. I recorded one video for the firing (it is in slow motion).
After successfully tested all the components, I started to think about what can I do with it. I received many wonderful comments from follows in IMA, and one advice among all of them was doing a high speed photography.
Section 2: Let’s start High Speed Photography
Inspired by the picture searched online and from the advice by Rudi and Cindy, I want to test whether the gun was powerful enough to break something like the a plastic bag filled with powder so we can capture some wonderful pictures like the one above.
I bought one kind of stive (an edible material in cooking) (shown below) and some very thin plastic bags to test. The test result is not good. It turned out I cannot impale the bag with dust inside, even it only contains a small part of it.
When I wanted to increase the power of coil gun (try to penetrate the powder bag), I increased my charge up to 250V (I nevered did this large), the circuit burned when I fired. I heard a very large sound and saw a spark. The circuit stop working. I could not charge up the circuit any more. I had to come up with alternatives (4 days till presentation).
After carefully examing the circuit, we found that it was due to the burn down of one transistor. I had to redo and reconstruct the whole circuit. The picture below is my orginal “fire button”, my voltage meter and the transistor. I took them off kept as a souvenir lol.
Section 3: more experiment on High speed photography
After fixing the circuit problem I had before, I continue on my experiment. This time, instead of trying to penetrate something, I just wanted to see some effects of impact. Thanks to the help from professor Rudi, I set up the my equipment as shown in the figure below. We used one adurino and two relays to control the gun and the camera. The light there is to provide enough tight for the photography since we would be shootting under 1/4000 shutter speed. After several trials, I adjusted a relatively good delay time between two devices (1500us) and took some photos. There are many points one should be attention to for the camera setting here:
- The shutter speed of the camera needs to be as fast as possible. For Canon 6D, the fastest we had is 1/4000. With a faster shutter speed, you will be able to capture faster objects clearly.
- Provide enough lights. Although the large aperture can give more incoming lights, it’s far not enough. A strong flash light or a consistant light source (like what I had) is very necessary.
- Switch the focus mode to manual focus. Auto focus will waste 1 sec in focusing every time it shoots and we cannot allow that. Adjust the focus to a proper focus distance and set to manual setting.
Let me also put on some pictures when I did countless experiments.
The synchronous between gun and camera needs to be adjusted carefully. For different energy in the capacitor, we need different delay time. For example, 100V —- 1500us, 150V —- 17500us and so on. This number need countless trials and fails, so if someone in the future wants to do this again, don’t give up.
Section 4. My Work
After countless trials (more than 300 pictures), I had some successful pictures. Please enjoy them below.
In the above, I put on 6 groups of photos. One group of photo (besides group 6) contains two pictures. The first one is 1 second before the impact on the dust and the second one is the impact effects. If you can put two pictures together for comparison, you will see the effects. For group 6, I am shooting a jelly. The picture recorded the exact moment when the bullet get inside the jelly.
As you can see, I chose 3 different materials: dust, potato chips and jelly. I chose them because my gun is not powerful enough to penetrate something like an apple or a bottle.
Section 5: Conclusion and some thought
I believe high speed photography is a very charming category in the photography family. It can capture the moment that cannot be seen by human eyes and that’s what makes it unique. However, it’s unique and very hard to capture. You have the contrains in the camera side, the gun side, the lighting device. Despite every device is properly set, you still need many tries before you can actually see something.
I didn’t start this project considering I will do high speed photography, so I just had about 3 days to do the shooting adjustment. If I had more time or I made the decision earlier, I would definitely have some more beautiful pictures. Next time someone try to do this, he should keep a good recording of the setting of each shooting: how many charges are in the capacitor, what’s the distance between the gun and the camera, how many microseconds should the delay be…… If one wants to use a more powerful gun (such as a real gun), the shutter speed might need to be quicker so you might need a more professional camera. This is a difficult task both from the aspect of device constrains, and from the aspect of the efforts you need to put on.
I considered my work in this project is satisfactory but far from a good work. This is a very wide aspect of photography and so many artists put years of work into it. This even deserves an entire class to introduce it. I learned a lot from this project and during the whole process. I have writen most of my experiences and learning outcomes in this blog, but if you have specific questions regarding any parts I did, I will be happy to help!
Section 6: Thanks
Special thanks to all the IMA fellows who gave me advices, helps and supports. Thanks Kevin who brought me 4 capacitors from electronic markets although I did put them into use (due to the constrain of time). Thanks Shawn, who came up with the idea of electromagnetic gun in the midterm and I stole it. Thanks Rudy, who supports me all the way in this class! Without all the helps, I couldn’t learn this much and finish this. Thanks to the show, I had the chance to display my work to others. I really didn’t expect that many people were interested in my work! Thanks for all the good words!