Which is better for me: Basic Stamp II or Propeller? (multiple stepper motor co

Mr. Bungle

Hello!

I'm planning to undertake a project involving stepper motors, and I'm looking for some guidance on which Parallax kit(s) might be best for me. This will be a motion-control rig for an HD video camera, and while I'll probably start out basic (just controlling focus & zoom via gears and a pair of stepper motors), I'd eventually like to control the camera on multiple axes, including a motorized dolly. I'm aiming for programmable movement and highly repeatable actions so that I can composite multiple camera takes together with pixel precision. This would involve up to 7 stepper motors operating on a studio set.

I tinkered with this about 6-7 years ago with a Basic Stamp II module (I got one stepper motor wired up and taking commands), but I've since sold my electronics gear and I'm likely to be pretty rusty on microcontroller and electronics concepts. I am a programmer by trade (freelance web development) and have been programming nearly all my life, so that aspect doesn't intimidate me; but, I'm still an amateur when it comes to principles of electricity and electronics.

The big question is: would I be better off starting simple with another Basic Stamp II kit (and if so, which one(s)?), or might I be able to tackle a Propeller kit? How many stepper motors can I control simultaneously from either kit? I've read up a bit on the Propeller, but I'm still not sure that I understand it completely. I'm fine with buying something simple and then moving up when I'm ready, but I'd like to avoid having to learn 2 separate interfaces and programming languages if I can avoid it.

Thanks in advance for any help - and please let me know if I've left out any details.

Graham Stabler

A protoboard is a good bet, you have 32pins of IO so you can control a lot of steppers (assuming step and direction drivers are used it could be 16).

I'd give the propeller a whirl, if you want to it will allow you to add a lovely user interface and it has plenty of speed which is ideal for motion stuff and once you get the basics its really easy to knock up simple tests, the prop terminal program by Ariba also gives you mouse/keyboard and TV through your PC when testing.

Controlling steppers on the prop is pretty easy, either in spin or assembly, you can also use the counters to produce variable frequency pulse trains as another means of control.

Graham

OzStamp

Hi Mr Bungle.

Start with the Propeller.. controlling multiple stepper motors with a Basic Stamp is very limiting..
Propeller Proto board or get some grease on your hands and start with the Propeller DIP + eeprom + crystal
and the Propeller plug or Prop clip ..

I am sure the Propeller is the best option for your project...ir if you have 10K + spare buy an off the shelf
4-5 axis motion controller with servo motors etc etc

Cheers
Ronald Nollet OZ

Mike Green

No matter what controller you use, you will need some kind of motor driver to handle the power switching. You can make your own using power transistors or you can buy any of a variety of commercial controllers that do varying amounts of the details of moving the motors. You will need some kind of position feedback device, at least a "power on calibrate" sort of thing so the controller knows the initial stepper position and can recalibrate from time to time in case things "slip". If you use a fancy motor controller, you'd have no problem using a Stamp. These use a serial channel for control and a Stamp can handle several, one at a time ... which is ok.

Here's a sample stepper driver: www.nutsvolts.com/PDF_Files/stepper.pdf.

You could use either a Stamp or a Propeller with this since each stepper needs 2 I/O pins. With a Stamp, that doesn't leave enough I/O pins for much else. I'd suggest using a Propeller. It will let you do things faster, more smoothly, and the whole thing can be run from a keyboard/display provided by the Propeller. You would be able to record sequences on an SD card if you wish or just use some EEPROM.

Lawson

I'd recommend starting with a Propeller kit. The demo-board is a great tool to learn on, and a Proto-Board is an ideal blank slate to start a project with.

The basic stamps can control many steppers, but getting more than one to move at once will be difficult. With the Propeller you should be able to control 2x the steppers, (32 vs 16 pins) and have ALL of them moving at once. Being able to do eight things all at the same time is sooo nice in a machine control application like this.

What's so hard to understand about the Propeller? It is eight microprocessors on a single chip that run independently of each other and can all access a shared memory and I/O pins. Spin is no worse than any other programming language I've learned, and with the Prop cranked up to 80MHz it's pretty fast too.

My two cents,
Marty

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Lunch cures all problems! have you had lunch?

Graham Stabler

Properly sized steppers don't slip but a home switch will be needed so you can start from power off.

The hobby CNC world is a great source of drivers and they tend to be more in to performance. The usual thing is to drive the stepper motor at up to 20X its rated voltage but with a chopper current limit set to the rated current, this maintains torque at high speed. Good drivers also counteract mid-band resonances.

good 3/4 axis kits:

http://www.xylotex.com/

Drives for big motors and servos that you can drive like a stepper:

www.geckodrive.com

Graham

RinksCustoms

for program size and from a linguistical point of view, comming into the prop with the BASICs already behind you, the prop would propably be the better choice. it's got oodles more memory and is ALOT faster with the execution of the program. Not to mentiona host of other advantages that a parallel proccessing video integrated chip offers.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
E³ = Thought

http://folding.stanford.edu/·- Donating some CPU/GPU downtime just might lead to a cure for cancer! My team stats.

Mr. Bungle

WOW, thank you guys so much - you're great!

This is a lot of information to digest, but I most definitely appreciate every single bit of it. It sounds like the Propeller is the way to go, and it certainly seems to be capable of everything that I'm hoping to do with it.

I don't want to jump into the deep end right away; would it make sense to start with a Propeller Education Kit and go through the lessons and labs, or should I pick up the Demo Board and go from there? I'm unsure if the Demo Board will do enough handholding, which I may need to get a hold on the Propeller.

Mike, I'm looking at that link that you included, and I'm definitely going to keep that approach in mind - do I understand correctly that I'd need to build one of those per motor?

With the Basic Stamp II, as I recall I followed a tutorial from Parallax to control a stepper motor using a Darlington Array; is anyone aware of a stepper motor tutorial for the Propeller, or some sort of instructions to get me started? I downloaded and browsed the manual, but I didn't notice any specific mention of stepper motors.

Thanks again, everyone, for your help!

Skogsgurra

I am a bit late to comment this thread. But, my thinking is that there is no reason at all, be it cost, "easyness" or other to go for anything but the propeller. The BasicStamp will not help you learning the Propeller - they are simply soo very different. You will only lose time and confuse yourself if you go via the BS. Also, the ProtoBoard is a perfect platform for anything you need to do. Lots of free I/O.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

Mike Green

Yes, you would need something like that driver for each motor. Remember that the article is about a very general purpose motor development system where the driver can actually run the motor by itself at variable speed. You only need the actual driver IC and the connections to the motor and the microcontroller. There are other stepper drivers available and I'm sure they all have application notes and sample designs, etc.

You can certainly control a stepper with just a couple of Darlington transistors and the same Darlington arrays (ULN2803 etc.) can be used with the Propeller. These driver ICs allow you to use just two I/O pins to set the direction and step the motor. The Propeller has enough I/O pins to allow you to use the Darlington arrays if that's what you want to do.

A number of people have discussed Propellers and stepper drivers in different threads over time, but I don't have any links to them. Someone else may have the links or you may just have to search for them here.

You can do a lot of the PEK tutorials with the Demo board if you get (or have) the parts involved. You can also get a Protoboard with the Accessories kit, add a breadboard for the experimenting and some header sockets on the Protoboard to allow you to easily connect to the breadboard.

Mr. Bungle

Thanks for your input, Skogsgurra - that sounds like good advice. It seems like the major difference to the Propeller (for my purposes, at least) lies in the programming side of things, and that's fortunately the one area that I'm most comfortable with.

Mike, thanks again for your help! I think I might try to go the Darlington route, since that was the path I began with the BS-2 years ago. I did some searching through the forums, and found some useful threads that I think will help to get me started. I think I might skip the PEK and try the Protoboard route that you recommended - that way if I find I need more handholding, I can always put the protoboard on the shelf while I order a PEK and come back to it when I'm more knowledgeable and ready to advance my project.

I'm about to place an order, so I'll keep everyone posted with my progress. I'm sure to have a lot of questions down the road - you guys have been great!