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Hopefully I'm in the right place...(Project help needed please)

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James39

New Member
Hey all, I'm new both here and to the world of robotics, so please forgive me if I have a hard time following or don't know how to convey my query properly. Also excuse me for this being very wordy and more in depth than it likely needs to be, I don't know what about my project is important to mention.

As a little background on the reason for my project: I am formerly a photographer by trade, and for fun I still enjoy taking panoramic photos by putting the camera on a tripod and rotating it a bit at a time both horizontally and vertically and using all of the photos (usually a few hundred) to make one photo with weird warped perspective and a 360 degree view. This can be a pain to do and I often end up missing small sections and ruining the whole thing; and also it needs to be done quickly so clouds or anything moving will line up-or to not miss the rapidly dimming light during a sunset. Often times I do this while traveling and one missed section or moment wasted is totally disheartening when I get back home from a trip, anticipating the final result the whole way back, and realize it's not going to work.

My idea is to build a robot of sorts to do the work for me, rotating in small increments to be sure to capture everything, while working much faster and precisely than I can. I am aware that a product exists that does this, but it is meant for small consumer point and shoot cameras, not larger DSLR cameras like I use. Combined with the ridiculous price tag, I decided to just build something tailored to my exact needs. All I really have so far is an idea of the frame required (basically a "U" shaped set of arms with the camera bridged across the top of the on a plate that can rotate around a horizontal axis; the whole thing on another plate to rotate it around a vertical axis while mounted on a sturdy tripod) but while I can handle the design and fabrication of the frame just fine, I lack any knowledge of the other hardware and software required to automate my contraption.

I assume I would want to use stepper motors with a relatively fine degree of rotation (I typically go 5 degrees at a time according to the hash marks on my tripod,) though I'm not sure what size/power is needed-especially for rotating the camera around the horizontal axis. The camera (2 pounds) and plate (>1lb) would be fairly centered on the axis of rotation; the lens (approx 2 lb) will extend out about 5.5 inches off of the axis of rotation. I'd imagine the motor for the vertical axis doesn't need to be nearly as powerful since it doesn't really have any leverage against it due to gravity, but I plan on using identical motors just to make things easier for me to learn. I've done some looking and only really came across ones that seem like they would be too small. I'm also not sure if I know if I need a Unipolar or Bipolar motor.

While I am a bit confused about the motors, what REALLY escapes me is the other hardware to back up the motors operation. I'm obviously going to need a controller of some sort, as well as a power supply. I can figure out the battery situation once I know my system and its requirements, so my main concern is the controller. How am I to know if my controller will be compatible with whatever motors I choose or if it will be able to perform the functions I want? In addition to wanting a few different options as far as the pattern of rotation, I also need to have an option for a time interval between movements in the event of long exposures. Finally, I need to be able to program an additional port to fire the shot, either through an electronic cable release spliced in somehow (I believe they are basic enough to find a way for that to work), or a solenoid physically depressing the button. I'm guessing that even the most basic controller would be up to the task, but I don't know how to tell for sure what I need to get. I've seen drivers for sale as a "related product" while browsing for motors, is this something different from the controller? As far as the programming aspect, I have a friend who is proficient in a few different programming languages and is willing to walk me though that part of the process. I just need to get to the point where I have something to program.

Sorry for running on so long, I just wanted to make sure I didn't leave anything out. I'm still doing my own research, but I wanted to put this question up for you guys to see so as to give it time to be seen and all that, should anyone chose to reply. I'm anxious to figure all of this out and start building. If I have come to the wrong place in search of advice, perhaps you could point me in the right direction.

Thank you for your time and have a good day!
 
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Sceadwian

Banned
Between unipolar and bipolar, unipolar are usually much easier to drive. Biipolars require the current to be reversed in some coils during the stepping sequence which electrically tricky sometimes, where a unipolar motor require a simple binary progression of positive pulses, bipolar stepper drivers are pretty easy to make. If you search the forums here you'll probably find at least a half dozen threads about them. If you gear the steppers you will be able to control rotation/tilt of the head pretty precisely, sub degree depending on how you gear it. The hard part would be actually making the mechanical bits work. As far as a controller goes you just need to make sure you have enough I/O lines, you need 4 for each stepper motor, and maybe twice that for any possible extra needs for I/O lines that may come up. 16 I/O lines is not hard to find on a micro controller.

blueroomelectronics - Smart Kits Build Smart People
Blueroom is a frequent poster here and makes some REALLY nice looking PIC kits.

www.sparkfun.com
Also sells many different AVR and PIC development kits. Shop around see what you like, many of them will work. I prefer AVR myself but many people here prefer PIC's

Both PIC's and AVR's can be programmed in basic so it's very friendly to novice users. The actual part that drives the stepper motor is an IC or mosfet based driver because micro controllers themselves can't power much of anything, they just drive the power electronis that do. If you have trouble finding refrences using the forums search function go to Google's "Advanced Search" And limit the search results to www.eletro-tech-online.com as Googles search engine is much better than the boards.
You should be able to start construction on the motorized part of the tripod before you even decide on a controller. If you don't know where to go some of the other people here should be able to recommend a good website to go to for mechanicals.
 
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Triode

Active Member
If you want to spend around $10 and simplify it a bit, there are chips that will take a few signals from your controller and generate the pulses for a stepper motor. It's not that hard to generate the needed pulse sequence yourself, but the chips im refering to just take 3 to 6 inputs, one which is set to high to enable the system, one which is high or low to set direction, and one that you send a pulse to whenever you want a step, often one to select full or half step is also used. The L297 and L298 for example, are designed to go together, the '97 generates the pulse order and the '98 amplifies it, their datasheets include a complete circuit diagram of how to build a controller out of the two, the chips cost about $5 together. The total list of parts shouldent cost too much.

http://www.datasheetcatalog.org/datasheet2/c/0g0gh362kxwx30o7xi4x2i4jzffy.pdf

the diagram is on Pg.8

There are certainly other options, but I like this way because you can get a diagram specifically for the chips your using for free, and the parts arent very expensive. If your going to get into robotics in general then you might want to learn more about how the stepper sequence is generated for yourself, but this is a good short cut, and they include fatures like syncronization if your using multiple motors.

By the way, you probably already thought of this, but on the mechanical side of things, you should definitely counterweight the camera so that it doesnt take substantial holding force to keep it positioned vertically, its just easier on the motors that way, and it uses less power.
 
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Triode

Active Member
yeah, i pasted the link wrong, also the chips are about $15 together now, they used to have them at a site called All electronics for pretty cheap, but you cant get them both there anymore. Still buying chips made to your purpose to supplement your microcontroller is always an option, and sometimes the cheapest one at that. Other times its just time saving enough to make it worth the extra.
 

be80be

Well-Known Member
Lol you change it I posted one for you you can get them for $10.00
 
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