Camera Axe 5 Contest

For those not familiar with the Camera Axe or what it does check out

In the past I’ve always designed a product and then released it as open source when it’s done. While this seems to be the more common model for open source hardware, it obviously isn’t ideal since the community feedback won’t have an impact until the next version. This time I’m publishing an early rough version of the new Camera Axe hardware and having this contest to see if we can improve it before I finalize the design.

I’m planning to give away one of the new Camera Axes when their done to the winner. If the winner would rather have $100 credit on my store to buy sensors today I will allow that substitution. The winner will be chosen by me based on who I think gave the most helpful information. My decision is final. This could be a fix in my board design, a suggestion on how to save costs, a better part recommendation, a new feature, or anything else that helps me. To enter the contest you can either leave a comment at the end of this post, or you can also email me (ribblem ‘at’ If an idea shows up more than once the first person to suggest it will get credit. After the contest is done I’ll contact the winner via email. If you leave a comment below as admin I can see your email you enter so make sure you use the correct email. If I can’t reach the winner in 3 days I’ll try to contact whoever I thought was the next most helpful.

Here are the alpha PCB files for this new version of the Camera Axe.

If you have questions ask them below and I’ll do my best to answer them. Have fun and lets make the best Camera Axe possible!

Here’s a list of some of the big changes in this design since the previous version of the Camera Axe. These areas of the circuit would be the areas that most likely have bugs or could be improved.

  • Started using surface mount parts. The plan is all the surface mount parts will be pre-soldered even for the kits. This will make the kits easier to assemble. I needed to do this because the board is much more complex and some parts where only available as surface mount.
  • USB port is now included and an FT232 chip so no special FTDI programming cable is required. The USB port will also power the device.
  • Reworked the battery system to use a more efficient boost converter instead of a linear regulator. This also let me reduce the batteries from 6 AA to 2 AA.
  • Various other power efficiency improvements (Mosfet, better resistor choices, …).
  • Included an ICSP programmer header.
  • Added an LCD constant current source to more efficiently power the backlight. This will reduce power usage by more than half.
  • Added some 1M resistors to ground on the sensor ports. Hopefully this will fix the floating sensor pins when no sensor is plugged into a port.
  • Filter caps moved closer to pins they are filtering to reduce noise.
  • Added IO protection to the sensor pins.
  • Reworked Sensor1/2 pins so they should be more flexible for future sensors while maintaining backwards compatibility with existing sensors. These changes should allow IC2 sensors or a stepper motor controller per sensor port.
  • Lots of other little improvements.

This contest will be open through at least February 20th, 2011. I will update this post when it is officially closed.

I’m sure people will ask when this version will be done. The answer is that I’m not sure, but I hope to have it done in four months or less.

Update 1

Here is a list of changes I’m seriously considering. Basically I have added these to my PCB files and will only remove them again if I have a good reason to do so.

  • Integrated to a new and better boost converter to create 5V.
  • Added an Lithium battery charging circuit and plan to include a rechargable battery. This will increase cost a little, but get rid of the many problems mentioned about not having a battery compartment.
  • Added dedicated buttons to trigger camera/flash ports
  • Switched to a two color LED that connects directly to the shutter/focus pins on camera ports 1/2.
  • Added a battery charging LED.
  • Reworked a lot of the part layout to get filter caps closer to the pins that need them.
  • Added an internal header on the board for an optional real-time-clock board from sparkfun. This will require lots of code changes and I’m still unsure if I’ll support yet.

Update 2

And we have a winner. Congrats PTB! I’ve contacted him and he said that his version 4 is serving him well so he’s wants to wait for version 5.

While this officially ends the competition feel free to leave other ideas you have in the comments or post them to the Camera Axe forums. Ideas are always appreciated!

I’m going to finalize the PCB design and send for a few to be made. Then based on experience I’ll need to do at least 1 respin on a board this complex. Then I need to verify the final board version and hopefully the new software will be written. Then I know to get quantities of some of the parts is 8 weeks of lead time. Basically I think best case it will be 4 months before I have everything ready for a release, and it could be significantly more time. We’ll see how close this prediction is…

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High Speed Air-gap Flash

A bullet hitting a solid brass rod.

If you just want to buy an assembled and tested airgap flash, I have made an updated versions that can be purchased at Information Unlimited.

In my quest to capture amazing high speed photographs I notice that when photographing shooting bullets the bullets were blurred. I found that standard xenon tube, which standard flashes use, is very bright for the energy put into it because of glowing xenon gas. The book Electronic Flash Strobe by Harold Edgerton explains all the calculations, but in practice this means all the flashes from Nikon, Canon and others that use xenon flash tubes have a minimum duration of 1/40,000th of a second. That’s fast enough for most things, but not for a shooting bullet travels around 1000 feet/second. In 1/40,000th of a second that bullet can travel about 1/3rd of an inch leading to blurry photographs of bullets.

To solve this I had to make a faster flash. I’m certainly not the first to do this. I think that was Harold Edgerton. He actually created a company called EG&G to sell a product called the 549 Microflash, but that company has been dissolved and the product discontinued. Sometimes you can still find these flash units on ebay, but the ones I saw were selling for $8K+. There is also a company called Prism Science Works making a modern version of these for researchers, but you’ll need really deep pockets to afford one of those. I saw directions on how to build one in the August 1974 issue of Scientific America and emailed Alan who had already built a few. After this research I realized I could build a sub-microsecond flash for just a few hundred dollars. A sub-microsecond flash means the flash duration is less than 1/1,000,000th of a second or about 25 times faster than a xenon flash.

Here is an image showing how an air-gap flash compares to a standard flash when photographing a 1000 feet/sec pellet.

I am a strong believer in sharing knowledge so I’ll explain how I made my air-gap flash, but I am knowledgeable with high voltage safety procedures. You should not build this because this flash will kill you. It really will. This flash requires charging a 35,000 volt capacitor that will easily kill a person for a single mistake. I have a safety checklist that I use ever time I plug in this flash and it still scares me. If it didn’t scare me then I shouldn’t be using it because this thing is dangerous. The below information is for educational purposes only. Do not build one! If you go against my advice and do build one, I am not responsible for any injury, death, or any other problems it causes.

Here is a list of the main parts I used to build my air-gap flash:

Here is an overall diagram of how all the parts fit together.

This is the schematic for the custom circuit board I made. Basically it doubles the 120V AC and uses an external signal to trigger the 45 kV transformer.

And here is a picture of my custom circuit board.

Here is a picture of the air-gap flash.

This shows what is plugged into the air-gap flash. 120V to run the 45K trigger transformer, 14V to charge the big capacitor, and a 3.5mm cable to use for triggering.

Here is a side view. Notice that the reflector has a thin sheet of Plexiglas over it to make cleanup easier. The metal reflector is also grounded in case the plexiglass tubes shatter, and they do shatter sometimes. I have found they last longer if I use latex gloves so no oils from my hands get on the glass tubes.

This is a close up of the glass tubes where the spark happens. The outer glass tube is just for protection and to reduce noise. The inner tube has the wire 45 kV trigger transformer inside. When that transformer is triggered the air ionizes and that cases the big capacitor to discharge in a 1.5 inch spark that creates the flash of light. To seal the inner tube I melt one end with a torch until it is sealed.

A top down view that shows how everything is connected.

This rod is very important. It is how I discharge the big capacitor after every use so I don’t die when I’m working on the flash.

Those extra wires and circles are there so I had an easy way to discharge the capacitor.

Note about using it with the Camera Axe. The Camera Axe only allows a trigger voltage of up to 20V. This has a trigger voltage of 240V so I needed to to put a high voltage protection circuit between this and the Camera Axe. There are many examples of these circuits on the web.

Here are a few results:

Glass rods being hit by a bullet.

A balloon being hit by a bullet.

Thanks Alan for your help and letting me use some of your amazing photos.

Comments (57)

Camera Axe 4

After six months of work, the fourth version of the Camera Axe is finally ready. For those new to the Camera Axe it’s a programmable camera and flash trigger with two sensor plugs that can be used for a wide range of sensors. It can do anything from timelapse to photographing a shooting bullet. For a little background information read about versions 1 and 3 of the Camera Axe. This version is open sourced under the Creative Commons Attribution NonCommercial 3.0 License. I do sell kits, assembled versions, and various sensors at my store.

Camera Axe Video:

Here is a list of improvements from version 3 to version 4 of the Camera Axe.

  • The screen is much larger and this makes the menuing system easier to use.
  • The case is is much nicer because I had custom cases made for this project.
  • Added two LEDs to indicate when the camera or flash is being triggered.
  • Much nicer 3.5mm jacks for the sensors and camera/flash plugs.
  • Added a dedicated external power plug for those wanting to use external power.
  • The buttons feel much nicer.
  • Batteries last four times longer.
  • A new microcontroller that has two times the space for more features in the future.
  • The software is a complete rewrite and has too many improvements to list, but I’ll mention the greatly improved intervalometer mode and the new fast trigger mode.
  • The kits are easier to assemble (no wires or drilling needed).

There’s more information information about sensors, reprogramming, flash/camera cables, and much more at

Here are a few images taken with the Camera Axe.

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Electric Eel Wheel 2 – An Electric Spinning Wheel

I’ve just finished the second version of my electric spinning wheel. My previous versions have more explanation of how electric spinning wheels work see here and here. I decided to use the original name of Electric Eel Wheel 2. (sarcasm)I really like this new idea I came up with of adding a “2” for the second version of a product. Good thing I open source my ideas, perhaps other products will start copying me on this great idea. (/sarcasm)

There a lot of improvements in the new version. Here’s a list:

  • Much high quality of motor with longer life
  • Lots of changes to greatly reduce noise (quiet running motor, nylon flanges, …)
  • Motor controller runs at lower temperatures
  • No soldering required so the kits easier to assemble
  • Custom enclosure to protect the electronics and create a more professional appearance
  • Larger bobbins (hold over 8 oz)

For lots of details like build guide, FAQs, and a link to a store that sells the Electric Eel Wheel visit the project’s main page.

Here is a video of the Electric Eel Wheel 2 being used:

Here are a few pics:

Don’t forget to visit

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Projectile Sensor #2

Due to a few request I decided to make some improvements over my original version of this sensor.

The major improvements are a new 3 PCB design, which makes this much more durable than the previous version. The other huge improvement is using the Honeywell SD5600 Optoschmitt Detector which has a fall time of 15 ns. Previously I was using a standard photo transistor which had a response time of 15 us. This new design is 1000x faster! This actually matters on faster bullets since sometimes the old sensor wouldn’t notice a fast small bullet. The SD5600 never misses.

The only downside to this new design is that it’s a little more expensive. Here’s the BOM.

  • Female Header
  • 2x 90 Degree Male Header
  • 2x 3.5mm Jacks
  • 2x IR Emitters
  • 2x Honeywell SD5600
  • 2x 1K Resistor
  • 2x Male/Male 3.5 mm Cable
    • This sensor has two IR sensors spaced exactly two inches apart. The user inputs the distance from the sensor to the desired position of the projectile when the picture is taken. Based on the time it takes the projectile to travel those two inches between the sensors, a velocity for the projectile can be determined. Since bullets and other projectiles basically travel at a constant velocity, it is easy for the microcontroller to calculate the delay in microseconds until the picture is taken.


      Here’s a link to the Eagle files I used to create the PCBs.

      Using the Projectile Sensor with the Camera Axe

      There are 3 PCBs and everything is labeled so it’s supper easy to plug them together. You will need the 3.0.04 or newer version of the Camera Axe software. Turn on the Camera Axe and hit menu until you get to the projectile menu. Set the distance you want the bullet to be from the second gate when the picture is taken and then push the right button until you get to the “Trigger on” menu for the projectile sensor and set this to low. Now hit the set button. If the sensor continuously displays the speed of the projectile that means the sensor boards aren’t lined up correctly. Look at it from the side and bend the boards so the emitter is pointed directly at the detectors. Once it’s sitting there waiting for a projectile put your finger through the two sensors and it will report back to you the speed of your finger. Once you get this it’s working.

      Mounting the Projectile Sensor

      I mounted a projectile sensor to my pellet gun and it is working great. The pellet’s velocity ranges from 985 feet/second to 1060 feet/second. Below are a bunch of pictures of how I did this mounting.


    Comments (10)

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