Entry Level Stepper Motor Control / What To Use?

I'm going to look into that. And Thanks!

I'll keep ya in the loop loop loop..

GA. I will second that suggestion.

Here is a link to some Arduino uno kits (with stepper motor) on Amazon. It is best to check out which ones contain a 'learning' manual, or a link to the manuals.

The Arduino site itself has a lot of useful info.

IMHO: You might want to go directly to the Adafruit, Sparkfun, or Canakit sites. You will pay a little more than the cheap knock-offs, but will get a better product, with better support and tutorials.

GA.

Canakit looks to be a bit pricey compared to Adafruit and Sparkfun. For example, I have the Arduino Starter Kit for which Canakit charges $100. My daughter and son-in-law bought this kit for me for my birthday and paid only $65. On the flip-side, they've got some nice products the others don't.

Adafruit has great prices but they're so popular that many of their items are out-of-stock.

Sparkfun is a great site and has a nice mix of products.

Years ago, I built an XY plotter using stepper motors. I built the drivers from scratch, using Johnson counters to generate phased square waves to drive the windings. (It was loads of fun to play with! )

Each motor driver requires two inputs, direction and step.

Now there are ICs that will drive two motors, and you can buy circuit boards to drive a stepper.

Or, as others have suggested, there is the Arduino solution.

I found something called a feather PCA9685 in a video that might be of use.. I wrote that down.. then i couldn't find it on the same site?

it's late. Great options. Much to learn. Good help. Thanks!

That product is designed for use with RC-style servos, not steppers. Big difference.

For controlling steppers, this plugs right into the Uno's headers. 19 bucks. Much more flexible as well, as it can be used to drive steppers, servos, and regular DC motors. This will drive two steppers.

Look up picaxe they do everything you need.

You are fully correct Pj3ns3n in what you say about PICAXE chips, I will expand a little on what they can do for the OP (or anyone else too!), as I feel the chips deserve that...

PICAXE chips are sold at prices that make Arduinos and their derivatives, look in comparison, to be quite quite expensive.....burning a chip, is not quite the disaster it might be on an Arduino, late on a Saturday night, as you will have spares!!

PICAXE chips start at around $2 for the bottom end, which will probably deliver all the power and easy programming that such a Stepper Motor type of test unit needs (plus a few extra components for interfacing of course!.)

Also having the possibility to have more PICAXE chips in a unit, each one doing its own particular "thing", while communicating with other such chips, not only allows possibly the "total" speed of such a tester unit to be effectively increased, but makes for very easy programming and fault finding.

All the manuals, and all of the software needed are simply free to download and use.....

Go to the following websites:-

PICAXE-Microcontrollers

The huge forum is here:-

Picaxe Online Forum

Programs can be developed very quickly in an extensive proprietary version of BASIC, that is very fast (4000 lines per second are easily achieved with just the internal clock running at 4Mhz, some PICAXE chips run at 64Mhz).

From the website:-

How fast does the PICAXE operate?

All PICAXE M2 and X2 microcontrollers have an internal resonator which operates at a default of 4MHz for M2 parts and 8MHz for X2 parts.
PICAXE M2 can run up to 32MHz using the internal resonator while PICAXE X2 can run up to 16MHz using the internal resonator and up to 64MHz using an external 16MHz resonator.

At 4MHz the PICAXE chips are executing one million instructions per second internally which, for typical I/O commands such as high, low and toggle, equates to around 4,000 BASIC commands per second. More complicated commands will take longer to execute and therefore fewer of those commands can be executed per second.

So some chips will execute program lines at up to 16 times of that, = Possibly 16 million lines per second!!!!

So I can highly recommend them for speed of programming (very easy to learn), ease of faultfinding, and speed of operation, (though this particular usage probably does not require anything particularly fast, steppers are a relatively slow, electro/mechanical device.)

All that is needed to start work are almost any old PC or Laptop, that the free editor can run on, some breadboards for development and easily found, cheap "strip-boards" to make the final devices.

.......though some people stay with the breadboards!!

Some PICAXE Chips, a down loader cable, (either USB or possibly COM if the PC/Laptop is REALLY old!)

A cheaper development system, with such worldwide support, I have yet to see or hear about.

Examples of interfacing to steppers are already in the documentation, possibly making the hardware build a very easy stage, plus programming examples that can easily be built on for own use.

Some examples can be perused here:-

Interfacing PICAXE to Stepper Motors

If you look on the first page of this (free) pdf manual download, you will notice that both Unipolar and Bipolar Stepper motors can be driven by PICAXE chips and a minimum of extra of hardware (probably same/similar hardware as an Arduino requires):-

PICAXE Manual Part 3

Even if you accidentally "Burn" a PICAXE chip, you can probably buy several dozen of them for the price of a single Arduino or similar......though I have yet to damage one myself....

Obviously, if someone already uses Arduino, they will stay with them, but of course the same can be said about people who understand PICAXE chips, so if you have no experience in this area at all, you can start where you wish!!

Thanks Andy for the backup. I have taught Picaxe for many years at GCSE and A level DT projects. They are as you say very easy to use with lots of info online. We have made plotters, sun finders, fish feeders, automated money boxes etc with steppers scavenged from old printers. Great fun. Make good data loggers to and can easily be made to transmit serial data back to P.C.s for plotting real time data. You can drive servos, motors, LEDs, LED Marixes and LCD displays. Lots of project ideas out there.

For this application the Picaxe would work fine but, for other apps that require faster processing, one concern I would have is that it appears to running a BASIC interpreter on-chip. On the website they speak of its executing 4000 instructions per second (4 MHz clock). That is not very brisk, all things considered. The Arduino is programmed in C++ which compiled and downloaded to the processor. It's very fast. I've one app where I'm reading 2 A/D channels at ~1 kHz each and processing the data (including median filtering) with idle time to spare. What has been your experience? Have you found the BASIC programming to be a bottleneck for certain apps?

How fast do you need to be for controlling a couple of motors? In fact, they are more than fast enough.....up to 16 million lines of BASIC code per second is a really useful amount of speed!!

Plus, the I2C interfacing and the many other types of external chips supported, are all made very easy to implement. The numbers of example interfaces support software are legion....

Though anyone with experience of using another chip (Arduino is a very good example), will probably not want to use a new chip.....understandably.

But for a total newcomer, he will find it easy to program and understand, the Arduino is nowhere near as easy....

So for for anyone starting from scratch, there is really nothing better around! Cheap, plus good FREE software and masses of help from both RevEd and the forum.

Also, as I mentioned earlier, by being SO cheap, you can purchase far MORE chips, each one doing a part of the processing needed, and communicating with the "master" chip when required! Which simplifies the overall programming significantly, by breaking it up into simpler blocks!

Helping with fault finding at the same time..

Doing all that with an Arduino is nowhere near to being so easy.....

I have used both, and the PICAXE wins hands down each and every time for me personally.....not just because of the exceedingly low price either.....but how they are SO easily interfaced to each other.....

Even if someone decides (unlikely!) to "throw out" the PICAXE version later in favour of another system, he will have managed to do it very cheaply, plus he can sell it off on ebay very easily......very low losses....

But each to his own of course!

Did you read the first sentence? What does the first sentence say, Andy?

"For this application the Picaxe would work fine but, for other apps that require faster processing,"

I was "clearing up" the statements....

I have to admit that I was never at a loss for speed when using them, but what have you made where their speed was simply "not enough", may I ask......that would be very, very interesting for me personally......

And like many here, it is obvious that certain "jobs" will simply not be possible, for the reasons stated...

Microchip also make AtMega compatible chips, that have even more performance than the original chips.....which may interest you....

What may interest some here is a comparison between Arduino and PICAXE:-

arduino-vs-picaxe

Which PICAXE wins 7:3 points!!

I await your reply with great interest!

The comparison is frivolous in a number of places. For example: Picaxe runs 28 servos vs Arduino's 20. Who runs even 20 servos? No one that I know of.

Dozens of lines to measure temperature? No, a couple of lines. Etc., etc.

Several flavours of Arduino use ATMega parts.

One thing he does conclude correctly: the picaxe is not fast. When you need speed, this is a killer. What did I need the speed for? VLF RF sampling. I would never consider the picaxe for this application. It is too slow by a wide margin.

For stepper-motor control? Either one is fine with me.

You wrote "...up to 16 million lines of BASIC code per second is a really useful amount of speed!!"

No. Not even close.

16 million (machine) instructions for a 16 MHz device (assuming its instruction set all take a single clock cycle to execute, probably not realistic), not 16 million lines of BASIC code per second. Thousands of lines per second, not millions. In fact this is what they say of their 4 MHz part (from the link you provided):

4000 per second for a 4 MHz part (x 8 for a 32 MHz part and we're still 32000 per second, not millions). Also consider that the high, low, and toggle I/O functions are fairly simple BASIC functions internally and still slow things to a crawl. More complicated functions slow things down even further. The reason? Most of the time isn't spent executing your program, it's spent running the interpreter.

You are being picky, as most code written for PICAXE actually does often have a single command per line, as it make fault finding far easier and the overhead is minimal to none, but as you may not have tried them, you could not be expected to know that.....

Piling more commands in a single line is usually bad programming, at least in PICAXE BASIC anyway. So the "line speed" is high, but you might possibly see that as "cheating".

But even if the speed is only a quarter of what I mentioned (it will usually be higher than that), they are still very fast chips, with the flexibility of BASIC, something many users quickly learn to appreciate.

You might also be mixing up PICAXE BASIC with way older BASICs (PC's GWBASIC for example) worked, as they were interpreted as the program ran, which of course makes things REALLY slow....though some could also be compiled if the need for more speed arose, but then suffered from heavy program overheads, making it still quite slow.

The biggest drawback for PICAXE BASIC to my mind is that it is not FP....but there are ways round that if you are careful.....and there are FP co-processors that could be interfaced if needed....I have never had the need myself....

Here is one that works well (I am told) with PICAXE chips over an I2C connection for someone needing fast FP maths:-

PICAXE Add-on-Modules uM-FPU-Floating-Point-Coprocessor

Here are a further few bits and pieces that you may find interesting, taken from the PICAXE website:-

1) Do symbols increase program length?

No. All symbols are converted back to 'numbers' by the computer software prior to download and so have no effect on program length.

You can use as many symbol commands as you wish.

2) Does the PICAXE support interrupts?

Yes. All M2 and X2 parts support a 'polled interrupt' on input pins using the setint command. The polled interrupt scans the input pins between every BASIC command (and constantly during pause commands), and so activates very quickly.
The X2 parts also support 'hardware interrupts' on specific input pins using the hintsetup command. Whenever a hardware pin interrupt is detected it is flagged until cleared.
Using the setintflags command allows the interrupt routine to be called between BASIC commands to respond to the hardware interrupt flags and other interrupt conditions.
The PICAXE uses the internal microcontroller interrupts for some of its BASIC commands (e.g. servo). Therefore the internal microcontroller interrupts are not available for general use.

3) Can I run more than one program at a time?

The PICAXE M2 parts support up to 8 separate program tasks which can be active at the same time.
The PICAXE 08M2 and 18M2 support up to 4 program tasks, the 14M2 and 20M2 support up to 8 program tasks.

4) How large can a PICAXE program be?

This varies on the commands used, as not all commands use the same amount of memory.
There is no fixed 'byte' formula as to memory usage e.g. pause 5, pause 50 and pause 500 will all take different amounts of memory space! To calculate memory usage use the 'Check Syntax' option from the PICAXE menu. This will report the amount of memory used.
As a rough guide, a PICAXE M2 can hold a program of between 600 to 1800 lines of code (ignoring blank lines, comments and 'symbol' definitions), a PICAXE X2 can hold 2000 to 3200 lines of code per program slot.
Some commands, such as sound and serout use more memory and so will reduce this count. In our experience most educational programs that are too long to download are generally badly composed, and can be greatly reduced in size by use of sub-procedures etc.

5) Can I see the assembler code downloaded into the PICAXE?

The BASIC commands are converted to a tokenised form when downloaded so are not stored within the PICAXE memory as either source code nor as assembler code.

6) Why use the PICAXE instead of assembler or C?

The PICAXE uses a simple BASIC language (or flowcharts) that younger students can start generating programs with within an hour of first use. It is much easier to learn and debug than either C or assembler code.
The second advantage is the direct cable download method. The software is free and so the only cost per computer is a low-cost download cable. This enables students to buy their own cable and for schools to equip every single computer with a download cable. Other systems that require an expensive programmer are generally too expensive to implement in this way.
Finally as the PICAXE chip never leaves the board, all leg damage (as can occur when the chip is moved back and forth from a programmer) is eliminated.

Here a clever way to go (found on the PICAXE Forum) if you really need speed:-

For me, if I need more speed than PicAxe provides, then I build the 'idea' using PicAxe (14M2 or 20M2) once I have this working I can then substitute a PIC16F1825 or 16F1829 which are pin compatible devises. For compiling a program for the PIC processors I use Great Cow Basic which is open source and compiles the source into PIC .hex files which can then be programmed using my GQ-4X programmer.
The overall solution isn't as flexible as the PicAxe version as I lose the simple programming link capabilities, but comparing the two devices (14M2 and 16F1825) in the same circuit using similar code (Great Cow Basic and PicAxe Basic are rather different dialects of Basic) with both devices run at 32MHz the 16F1825 was close to 20 times faster.
http://www.picaxeforum.co.uk/showthr...l=1#post278479
Still, I much prefer the whole ecosystem that PicAxe provides. I've got a couple of Arduino devices which look great, I've also got a couple of mBed devices, my 'problem' with both of these is that I find it hard to see how I can incorporate the processing devices from these (AVR or ARM) into a finished design. I find it hard to locate easy to understand and follow information on the fundamental support circuitry required to allow programming/reprogramming of devices and other support peripherals such as crystals/resonators. That is why although I've programmed the devices, they've stayed on the shelf yet the PicAxe (or PIC equivalent) have been built into designs which have gone on to be produced commercially.

I hope this was interesting for you.

Andy, look at its published speed: 4000 BASIC instructions per second on a 4 MHz part, one million machine instructions per second. That is 250 machine instructions executed per BASIC line, on average, and that for simple I/O instructions. Slower for more complex BASIC functions. They spell it out in plain English.

The BASIC interpreter is slowing this thing down to an absolute crawl. Where else is that time being spent? I/O instructions on Microchip parts are single machine instructions (ie, assembly, if you will), instructions that take one microsecond to execute, but by the time that BASIC interpreter has gotten round to executing a single line of BASIC code 250 microseconds have passed, average. 250 machine instructions, average, per BASIC line, using their benchmark. Again, where is that time being spent? Not on your program, guaranteed.

Arduino's C++ is compiled into machine instructions and those are downloaded to the chip. It is not interpreted. In complied C++ a write or read instruction to a port or register reduces to a single machine instruction and it would reduce to a single instruction on Microchip's part had they done the same. They chose interpreted BASIC for convenience, not speed. Had they chosen compiled BASIC it would be a helluva lot faster, but they didn't.

You did not read my last post through I feel. Not that it makes the PICAXE any faster!

But as previously mentioned,in some applications where speed may be important, using more chips and dividing the workload can often be used to advantage.

Also, as someone else mentioned, its a lot easier, where space is tight, to fit a few PICAXE chips in rather than an Arduino.

Plus those other AtMega chips that MicroChip also make, will "polish off" almost any equivalent units around....

As I mentioned earlier, several flavours of Arduino use ATMega parts. Nice parts and very fast.

I've been using Microchip's products since 1993 - 24 years now (25 as of May) - and I have been very happy with them. I would be much happier with Picaxe had Microchip chosen to use a compiled language, even BASIC. For comparatively slow stuff like stepper-motor control, no problemo; whatever works, but most of my apps typically need a bit more speed than an interpreted language can offer.

Did you not appreciate the usage of an identical PIC to the PICAXE, once the system "works", but needs speeding up?

The speed change is thought to be around 20 times, which is quite a massive difference to my mind!! Useful even!!

Furthermore, it is possible to completely "erase" a PICAXE, so that it reverts back to being the original PIC, then use the other BASIC compiler that I mentioned, to prepare the PIC for running at full, high speed!!

Maybe you overlooked it in my post?

To my mind, it makes the PICAXE even more flexible and therefore more useful than even I had thought about, even though I knew it was possible.....

Have a great day!

PS. The chips are more expensive in the US and Germany, than in the UK, but in the US vary around $3.50 upwards to around $12......

See here:-

US Prices of picaxe chips

20 times is a 'massive' speedup? You're joking, right?

Well if I had a car that would only do 50MPH, then paid a company to tune it up for a 20 times speed increase, that would make a slow car, faster than the speed of sound....

So applying that simply to a 64Mhz clocked PICAXE Chip, would (assuming my math is correct) be around 64,000,000 x 20 = 1,280,000,000 or over a Gigaherz, quite reasonable for a small and very cheap chip!!

Tell me (again and again) if I am missing something!

I have the opinion that something got up your nose recently, and that you want to take it out on me for some obtuse reason of your own making!!

You might think you are going to "WIN", but what do you perceive as winning?

I still say :-"*Manners maketh man!" Obviously you don't!!

* Manners-maketh-man

We need someone on CR4 with your experience with PICAXE, in fact, we have needed someone like you for several years now!!

How about you starting a sort of learning/training course for CR4ers here?

I am simply not experienced enough to do it alone, though I have plans to start using "them" again in the near future! But someone like yourself would be a boon for us all.....

What say you?

PICAXE chips are SOOOO flexible......

Start with a couple of steppers from an old inkjet printer and an Arduino $20, and a motor shield for it.

Arduino has a complete library of code contributed by the community and you can easily re-program to suit your needs.

Sorry for not getting back, I've been about. I think I like either of the suggestions; there doesn't seem to be a huge price difference in the US anyhow. What I'm curious about is which will take me from being able to work out a two servo motor to 3, 4, 5 or 6 without issues. I also want to work on programmable RGB LED lights for another use and want to carry over knowledge seamlessly, of course.

Download the manuals for PICAXE and have a read, that way you can decide better what you want to do and with what system.

The downloads are here, as are many other details of PICAXE usage:

PICAXE-Microcontrollers

Click on any of the headings and, eventually, "Manuals" should give you a good overall impression....

Then do the same for other systems that interest you, the Arduino for example....

..yeah.. that's about what I've been doing. and why I've been trying to find a modular solution.

I wouldn't mind getting a little of each system and seeing which one turns out to be more intuitive and therefore works for me first. Of course I love the idea of the lowest priced units for repeat-ability reasons. ..That's money best spent in any R&D

You've helped a lot. Thanks

That's why we are all here of course, to assist, but it is very kind of you to say thanks as well, not everyone does that!!

Thanks from us all.

I've sent a PM to A.W. asking him to give my initial parts list a once over.

Arduino / first on the board

..more later