Choosing a BS
fma38
Posts: 42
Hi,
I'm new to the BS world, and I need some advices. I plan to use a BS to drive an automatic pano-head, to make high resolution panos. The idea is to use an astronomic mount, like this one:
http://www.telescope.com/shopping/product/detailmain.jsp?itemID=227203&itemType=PRODUCT&iMainCat=6&iSubCat=24&iProductID=227203&relateInfo=1&add=yes#tabLink
Instead of a telescope,there will be a digital camera.
I need to drive 2 motors (I think it uses DC motors), and readback incremental encoders. The process is to turn the head in the horizontal axis with a precise value (accuracy < 0.5°), take a picture, then turn again. At the end of a row, turn a few degres on the other axis, and begin a new row.
My first idea was to use a Palm to make high level interface, communicating with the BS through IRDA. But maybe the BS can drive a little keyboard, and a LCD display.
What device should I choose? I plan to implement a PID to drive the DC motors, maybe through the Pololu driver. What power do I need? Is the cheaper BS (BS2, in fact) enough? Do you know if such project (or close) already exist? Where can I find routines for LCD/keyboard driving?
Thanks for your help,
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Frédéric
I'm new to the BS world, and I need some advices. I plan to use a BS to drive an automatic pano-head, to make high resolution panos. The idea is to use an astronomic mount, like this one:
http://www.telescope.com/shopping/product/detailmain.jsp?itemID=227203&itemType=PRODUCT&iMainCat=6&iSubCat=24&iProductID=227203&relateInfo=1&add=yes#tabLink
Instead of a telescope,there will be a digital camera.
I need to drive 2 motors (I think it uses DC motors), and readback incremental encoders. The process is to turn the head in the horizontal axis with a precise value (accuracy < 0.5°), take a picture, then turn again. At the end of a row, turn a few degres on the other axis, and begin a new row.
My first idea was to use a Palm to make high level interface, communicating with the BS through IRDA. But maybe the BS can drive a little keyboard, and a LCD display.
What device should I choose? I plan to implement a PID to drive the DC motors, maybe through the Pololu driver. What power do I need? Is the cheaper BS (BS2, in fact) enough? Do you know if such project (or close) already exist? Where can I find routines for LCD/keyboard driving?
Thanks for your help,
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Frédéric
Comments
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- Stephen
BS seems to me a better choice, as they are very popular.
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Fr
2) There's a tremendous amount of documentation available on the Stamps. On Parallax's website, look under Downloads. You'll see "Stamps in Class tutorials" and "Nuts and Volts articles". There are specific examples for using a 4x4 keypad in a Nuts and Volts article. I don't have the link currently, but it wouldn't hurt to scan the articles' titles and look at a few of them.
3) Most webstore pages in Parallax's online catalog have links to extensive documentation for the product involved. One of the LCD displays (www.parallax.com/detail.asp?product_id=30058) has a keypad interface built-in. The Stamp uses two pins to communication with the display using an asynchronous serial protocol.
4) For any kind of relatively open-ended project like yours, I'd use one of the BS2p models (BS2p/pe/px) because of the extra statements supported and the additional memory (compared to the BS2).
5) An excellent website for information on math / interfacing with sensors / timing information is www.emesystems.com.
I plan to use a Pololu Dual Serial Motor Controller to drive the motors, and a LS7366 (quadrature decoder/counter) to read encoders. About the LCD, the one you suggest is a little bit expensive for my needs; a 2x20 chars is enough. For the keyboard, I will make a simple-but-intuitive interface, using only 2 push-buttons (OK/Cancel), and a rotary encoder to increase/decrease input values.
What do you think about?
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Fr
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- Stephen
Well, I will first order the Pololu DC motor driver, and start to play arround. The user interface will be the last thing I will implement, as I discovered that BS2 can read/write values through the program/debug serial line [noparse]:o[/noparse]) This is very usefull to make quick tests!
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Fr
Although all the folks that replied know far more about the Stamp world that do I, I read the brief specs provided at the site you posted. To me, it almost seems as if you could hack the hand controller to interface to a BS2p version Stamp·to do everything you need. I base this·thought on the statement describing the product mentioned at the site you posted:·"Four directional buttons on the convenient hand controller allow you to quickly slew your [noparse][[/noparse]camera]" to the place you want. Do the four directional·buttons imply left, right, up, and down? If so, it sounds like all you need to do is buy described on the web site and a Stamp with a breadboard area and study and work and study and work night and day and night and day until the thing does what you want.
Sounds easy, doesn't it? (It probably is a lot easier than I implied above!)
Good luck!
--Bill
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You are what you write.
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Frédéric
I am going WAY OUT on a limb here, but can you hack into the encoder feedback, somehow?
In my investigations, it seems to me that one may attain great repeatability with gearmotors and commercial-grade encoders. You can obtain even better accuracy with steppers and commercial-grade encoders. The problem is the expense. Gearmotors may be had rather cheaply. The encoder for the gearmotor will cost about the same (more, maybe) as the gearmotor. The controller for the gearmotor--if the motor draws, say, more than 3 amps--will be costly.
In the stepper-world, about the same·situation exists. You can easily achieve great repeatability, but if you want to move something the least bit heavy at anything other than VERY slow speeds, you have to look at NEMA 23 (at least) frame size motors. For example, I have a heapie-cheapie NEMA 17 frame size stepper which I equipped with a 3:1 timing belt reduction that turns a rotary table. I am not sure I could turn the table without the 3:1 reduction. When you step up to a NEMA 23 size motor, torque problems tend to pretty much disappear . . . as far as my application and your application--which seems highly similar, go. With the proper NEMA 23 stepper, I can easily turn the table directly, thereby eliminating the gear reduction via the timing belt. (And, I think I have found·a source for inexpenisve steppers in higher torque capacities, along with the appropriate controllers.)
By the way, although my project is a little less than half finished, it might be ideal for what you are trying to do. I will have two rotary tables mounted one on the other at 90 degrees to each other. You could 'take a picture' slew left or right and take another picture, then raise the second table up a bit and take a picture and then slew the other way. Even the low-end mill tables that I am using are of far higher precision than anything you and I are likely to build.
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If you choose to post, I will watch your progress with great interest. Plus, if all my mistakes interest you, I have no problem sharing them!
·
--Bill
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You are what you write.
About our project, there are in fact 2 projects of motorized panohead. 1) a pro version 2) a cheap version. For the moment, I'm working on the second one, based on the astronomic mount. For this one, I will try to keep as much material as I can. But for the pro version, it will maybe build from scratch, and then, stepper motors with rotary tables is one of the solution I'm thinking about (I'm using such things for my work, but very expensive ones, because very accurate, not needed here. What are yours?).
We started a wiki page for the cheap version (but in french):
http://fr.wiki.autopano.net/T
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Fr