The Simplest DIY Motorized Gigapan Gear

As many of you have already discovered with a peek into my website, I love photography and especially 360° panoramas. Lately I've dived into the fascinating world of Gigapixel photography. So I bought a motorized tripod head and I've made some Gigapixel tests.
Although they're not huge (if you want to see a huge beautiful panorama give a look to Cannes 65 Gigapixel) they give you an idea of the power of the technique.
I then decided to build my own motorized panohead. This is a project I've had for last 3 or 4 years, and I always lacked of time. First idea was to use two step motors and a pic board as Arduino, to obtain a real versatile robot which would have make everybody green with envy ;-) as this one of Phil Warner which I've always admired.
Unfortunately (maybe not?) my project is changed a little, and I chose to design the simplest and cheapest motorized gear for panoramic photography.

The circumstance which is behind the projects is that the nice tripod head I already had allows to rotate around the vertical axes, and the knobs for horizontal rotation and other directions movements are independent. So I could loose (indeed I removed it) the little knob which locked the rotation, and I've discovered that the friction of the head is perfect to avoid unwanted movements.
Then I searched a way to make the head move at little steps, and meanwhile make a switch closing the contact of the shutter mechanism of the camera. One of the objectives was making something very small and light which doesn't need to modify substantially the tripod, and which could be removed if needed. So this project was born. Read next steps to know how I solved the various quests.

First of all I had to find an handy motor gear, better already with the right gear ratio and speed. This is a part of an old PC CD reader, it  took care of the CD shelf movement. I've disassembled some of those CD readers, so I've a few of these motor units. Then I needed another big gear because the speed of the last black one was too fast and the torque too low, so I've recovered this white gear which has the same tooth geometry of the other ones. 
You also can see the little switch and the steel pivot for the additional gear.

My though was to add a metal spike over the last gear so this should push the tripod head at each turn.
First of all I glued an aluminium pipe at the right distance from the black gear. So the two gears are accurately in contact one to each other. Then I glued the top nail inside the slot in the top side of the gear, and I inserted another spike on the bottom side, this last should act on the shutter switch.

This is nothing more than a little lever NO momentary switch. It has only two pins, the third (NC) is formerly cutted.
I blended the metal lever so that the nail on the gear (the one at the bottom side) would push it coming from one direction as from the opposite one. I glued the switch in the right position testing it with the gear in place. 

Now that I know the exact geometry of the spike which should push my tripod head, I can design the big gears with right diameter and number of teeth.
I explain you the mathematical method to calculate the right number of teeth for your telephoto lens. We'll need a simple scientific calculator for that.
Because we are interested in calculate the horizontal field of view (we'll call it hFOV) of a given lens for a given digital camera, we need two simple informations: the focal length of the lens and the horizontal dimension of the sensor.
Many digital camera have a "crop factor" to be applied to the sensor (usually 1.6), this is a number which defines the dimension of the sensor compared to the standard film 35mm wide. So if you know the "crop factor" we have the first information, e.g. if your crop factor is 1.6 the horizontal side of the sensor will be 35mm / 1.6 = 22mm, we'll call that number "width".
The focal length is simply written on any lens.

Following trigonometry rules we have that:
tan (hFOV / 2) = (width / 2) / focal length
and so:
hFOV = 2 x arctan (width / (2 x focal length))

From now it's simple, if we suppose an overlapping of about 30%, we'll have the right number of teeth for our gear:
hFOV x (100% - 30%) = 0.7 x hFOV
n°of teeth = 360 / (0.7 x hFOV)

Now it comes the time at which I wished to have a 3D printer or a CNC cutter with all my heart! Indeed I couldn't cut the gears with a motorized jig saw, because the friction melted the plastic sheet. I could have used wood, but the teeth are very narrow, and I liked this plastic material I had (I think it was the cover of a scanner or something similar), I thought it was easy to cut by hand. Indeed it was, but anyway the process has been sooo long.
I give you the pdf with the schemes of the gears, although they are made for the exact dimensions of my device, and maybe you need to make them different. I've glued the printed sheet on the plastic to have the shape to follow.

Here you see how I refined the edges of each tooth, and I've engraved a socket to create space for the knob bolt.
Everything is done twice because I decided to cut two different sets of gears, one with a total of 40 teeth and the other with 60 teeth. In this way I can choose the 40 teeth gear for about a focal length of 80-85mm, and the 60 teeth for the 135mm longest focal length of my zoom.

To assemble the two pairs of gears, and meanwhile keep them firmly attached at the tripod head, I designed some latches created with a spoke from a bike wheel. There are very sturdy, are stainless, and are a little flexible so to act as a spring around the head.

Indeed mounting them onto the tripod head, with an elastic around it which add more friction, we see everything is stable in place. Furthermore the knobs help to avoid the gears move.

It's time to find a good way to attach our gear to the tripod shaft. That take some days to come to my mind, but then I remembered that I have some plastic joints to connect a LED torch to the bike handlebars, or something similar. I've bought some of them for a few $ (€ here) and I'm so lucky to have one broken, so that I can use the functional half, the one with the fast lock. The diameter is right for the shaft of the tripod.

To attach my motor unit to the clamp I've used an aluminium plate, where I've drilled three holes and make it fit with the clamp flat side. You don't see it in the picture but if you cut a split in the round border of the clamp, and make the folded side of the aluminium plate fit inside it, you'll obtain that the plate couldn't rotate around the screw axis, and everything is locked better.

I drilled two holes in the match posizions on the side of the motor unit, so I could connect the two parts with little bolts and nuts.

Obviously you need a switch to turn on and off the gear. I needed to make the head turn in both directions, so I used a three positions switch, and I linked the pins so that in center position power source is disconnected, and between one side and the other the wires are inverted.
I fastened the switch to a piece of plastic which I've glued in a convenient position. 

I've bought some short connectors for the Canon cameras, with 2.5mm jack at one side, and the C3/N3 (I've not yet understood which is the right name, maybe one is of the plug and the other is of the jack) connector at the other side. So it should be nice to use a 2.5mm female plug for connection to the gear. I've not one of them, so I've used a part of an old Nokia cellphone. It also has the 2.1mm power plug, so I'll use it for an external PSU (this should be an upgrade).
I've cut the mic socket so that the double plug will fit into a place under the motor unit. 
Another solution could be make yourself a plug for your camera, look my other instructables "DIY C3/N3 remote control plug for Canon DSLR".

After having cutted a few the plastic side, I glued the double plug in place and I've soldered the switch wires to the plug pins. You have to connect together the pins of focus and shutter lines  Don't connect together focus and shutter pins because then you shouldn't be able to only focus with half-pressing the camera button. Instead solder only the wires to shutter anf ground pins.
As power I've used three AAA cells, I've tested that they're powerful enough to let me make a pair of gigapixel panoramas. Anyway I could use the DC-IN plug of the Nokia piece to add a switching regulator and use an external psu.

Everything is now ready. I left the two short side of the motor unit because I wanted to cover it to protect the gears, but I've not yet a definite thought about that.

Now we only need to fasten the big gears to the tripod head and the motor unit to the tripod shaft. You can see how the nail came in contact with the plastic gear. I've designed the mechanism so that the contact on the shutter switch is closed when the nail is farthest from the gear. In this way the camera should have the time to rest after the movement, and also the time to shot the picture before moving on the next step...

Let's turn it on, first time without the camera, foreseeing a nice day to test it outdoor.

 

I'll post soon a gigapixel panorama taken with this gear. It will not be huge, because the number of teeth of the gears are designed for about 80 or 150mm lenses (with a crop factor of 1.6). I've taken the first three gigapixel pictures on www.gigapan.com with a focal lenght of 135mm (and a commercial motorized head) so you can get a sense of the resolution.

Look on this IMPROVED VERSION where I modified the motor unito to match with a new terrific perspex laser-cutted 90 teeth gear ;-)

Let's know your considerations ;-) 
Bye!

The first panorama turned out technically very good. As you can see from the screenshot lines and columns are good aligned. I've used 135 mm and the 60 teeth gear, but I've seen that overlapping is very large (about 30%) so I've the margin to use a longer lens too. Here you can see a video of the gear in motion.



And the final result on www.gigapan.com :-)