companies selling reliable microcontrollers and sensors....

Microcontrollers with a built-in high level language, like the BASIC Stamp, are great for starting out. There's also the OOPic, which I personally like, the BasicX, and several others. Support with plenty of example is important. This is one reason the Stamp is so popular, because Parallax supports its products very well.

From there I'd look into a microcontroller programmed via high-level language via a compiler. My personal favorite is the Atmel AVR line of

8-bit microcontrollers, using either Bascom or gcc. There's also the PIC microcontroller, and it has its own wide variety of compilers.

-- Gordon

I started out with the boebot and although I was already advanced in terms of programming and digital design skills, it was a great intro to basic robotics, sensors and motion control. Pretty reasonably priced as well and the support was great. I agree with Gorden, the AVR line is a good choice after that.

Shawn

Hi,

I would also recommend the atmel/bascom route. Being a compiled language you get the best of both worlds (speed of writing/debugging code and speed of execution).

Also the demo version of bascom allows up to 4Kb code which is alot, believe me. My camera controller base (MEGA8515,NE2000 network card + UDP stack, 2 RC servos, VFD display and some LEDs) fits in about 3.5Kb.

Regards Ian Dobson

Home of the Atmel based UDP mobile web cam

mails scanned with av-filter.pl (F-Prot / perl)

"Mark Smith" schrieb im Newsbeitrag news: snipped-for-privacy@i39g2000cwa.googlegroups.com...

For lurkers, Ian is very active on the Bascom forum, which is a great source for support, robotics and otherwise. I am constantly learning from Ian's posts!

-- Gordon

robotic

various

I highly recommend the Parallax products as well as the company. Their support to me has been top notch, at times going above and beyond the call of duty.

My first "real" bot used a Basic Stamp clone - the "counterfeit controller" by Scott Edwards. When it comes to programming, I tend to strongly favor C / C++, but there is nothing wrong with PBasic at all ! I have owned several Basic Stamp products, and have never had any problem reselling them on eBay after I satisfied my learning curve and/or wanted to move on to something else, so I

*highly* recommend them.

Reference:

James C. Deen

Let me answer the sensor question first. I like two companies that sell sensors. One is

which is very reasonably priced. The second is for a wide range of sensors. I'm sure there are other resellers of sensors, but these are my personal first choices.

Now. Comparing processors and the companies that make them is and always will be somewhat of a religious issue. Different people prefer different models, just as there are loyal Ford, GM, and Chrysler owners, then a few, who select particular cars for features per price, rather than by manufacturer. Different strokes for different folks.

Still, since you asked, I feel I can respond. Please note my commercial bias and understand I have a vested interests in what I say. Don't think that doesn't mean I am not 100% sincere about what I say, though. For reference, I am also a Senior Adjunct Instructor teaching robotics at a university at the upper undergraduate/graduate level.

My company

sells very reliable microcontrollers, and we've been doing it about 10 year before Parallax got started at it. Our current 'Pod controllers about 10 years newer, more-modern design than the Basic Stamp, are excellent for motion control, and particularly robotics. I think they are muh a better choice, and I doubt you will outgrow them anytime soon.

There are many other owners of companies which supply boards which post here, who also make excellent boards, which I think would be better to start with than Basic Stamps. Dan Michaels

for PICs and Brian Dean for AVRs come to mind.

Since you ask about using Parallax as a starting point, in my opinion, if you are a beginner and want to progress to the end goal of being an advanced beginner, it will do. If you want to really progress beyond being a beginner, you will need (sooner or later) to leave Basic and stamps behind. So to me, the issue is how much do you learn using Basic and stamps, vs., how much do you learn to do wrong. To wit:

The Parallax Basic Stamp can only do one thing at a time. As a result, you can easily learn how to write a program to control one thing at a time. (No robot of significant utility can be programmed that way.) You also learn some very bad design habits when you try to control more than one thing at a time, in my opinion.

For instance, you can control one RC Servo by using pulse generation command, PULSOUT. But for the milliseconds the processor is doing this, you can not do anything else. Then for another 18 to 19 milliseconds, you should not output a pulse.While the processor is doing this, you can not do anything else. If you use the PAUSE command to get this quiet time right, all your processing power is consumed driving that one Servo. You can't control another thing, not even a second RC Servo on your robot's other wheel.

Consequently, for a two wheeled robot, you will usually have to cheat on the timing. You do two PULSOUT commands in a row, then hope other processing is done roughly at 16 milliseconds. You hope you get close enough to fool the Servos into seeing it as a valid refresh cycle. Or you can't drive your robot reliably. And you can forget about reading a serial channel with a long string, or timing something else like the echo from sonar ranger. etc.

See their own forums to verify this is the case:

So what do you learn to do here using a stamp? Well, most folks quickly learn it is easy to program a stamp to do one thing. They then learn its hard to do useful programming with three or four things going on at once, and never get much further. Or they conclude they need more micros to get several things done. Some folks buy a Serial Servo Controller (about the price of another Basic Stamp) to be able to off load the RC Servos from the stamp. Later they start splitting up the tasks using more and more controllers either stamps, or by then, PIC's or AVR's programmed in some other language, each doing one thing at a time (plus a second task of talking to a central controller telling them what to do which is hard to do while controlling the one thing).

But virtually no one learns the "right" way, the way serious roboticists and programming professionals do multitasking on several complex problems at once, from a Basic Stamp.

I started learning BASIC as about my fifth language, in the early '70's, well before it came to microcomputers. I liked it so much (not), I soon switched to assembler for micros. Since 1980, when I went to work for Rockwell as a professional, I've seldom touched Basic for my own use.

Also, from my experience as a supplier of Basic as well as other languages on some of our past products, I've found the programmers using Basic are often the most lost, and need the most help completing their projects.

Likewise, others have noted problems. For example, most non-beginers are aware of things like this, taken from Wikipedia BASIC article: "In a

1968 article, Dutch computer scientist Edsger Dijkstra considered programming languages using GOTO statements for program structuring purposes harmful for the productivity of the programmer as well as the quality of the resulting code..."

I think you'll find plenty of amatuers that will vouch for Basic. Many professionals got their start, or had early experience as did I, with Basic. But I doubt you can find many serious professionals who would recommend it today, beyond as a beginner's first stepping stone. I can't even do that, because I think you learn bad habits which are hard to unlearn later.

Thanks for the mention, Randy.

Regarding the Stamps, I'll be the first to say that they do have excellent documentation. I was looking through one of their manuals a few years ago on the Stamp and was very impressed with the explanations about some of the very basic fundamentals. My impression was that the documentation was geared to the very uninitiated beginner, and even then, to those of very limited technical experience

- to the point of explaining the barest of fundamental concepts.

If you fit into that category, they are probably an excellent starting point.

But I will dispell a myth - even rank beginners can pick up an Atmel AVR, PIC, or other bare chip or board and start from there. Randy's Pod's would fit into that category too. You don't have to start in the childproof section where all the tables have padded corners and all the outlets are covered and breakables are put high up out of reach. After all, many folks that come to amateur robotics already have a good bit of experience in at least one aspect of the field whether it be programming, electronics, mechanical, or other discipline. So why choose a route that assumes little or no experience with limited growth potential?

Admittedly many of my customers are experienced folks who know exactly what they want. They don't ask for help, they don't need it - they buy their boards and start right away putting them to use solving real world problems. However, occasionally I'll get someone who's never programmed a microcontroller before, but knows some programming, and wants to learn programming or maybe has a project in mind and chooses one of my boards as the basis to solve it. There have been sooo many times I will tell you that after just a few questions that we work through, usually by e-mail, that person is off and running and never looking back. I've had folks that started off with many questions like "how do I control a pin" or "measure a pulse width" or "control a servo" since they had no microcontroller experience. Many times those same people end up developing the most amazing things. I will also say that, on a personal level, it is a wonderful experience to be a part of that.

What is the common thread among these successful people? First off, they _want_ to learn and have a burning desire to accomplish their goals. They are tenacious - there are so many little things to trip you up when working with computers and robots. When something doesn't work right the first time, and believe me it rarely does, chances are there is not some fundamental design flaw or compiler bug that you are the very first to uncover on your very first project that the many thousands before you have somehow not noticed. Chances are, it is something small - wire connected to the wrong pin, ground from your controller to your sensor/servo/display is not connected, forgot to enable a pin as an output and thus it can't drive the LED, etc, etc. You have to be able to not get too frustrated, think logically and patiently enough to troubleshoot the problem by "eliminating the impossible", what remains, no matter how improbable, must be the answer to paraphrase Sherlock Holmes.

Second, they ask questions and _listen_ to the answers. None of us knows everything and even highly experience folks get stuck every once and a while. But to get help, you need to be able to formulate your question such that you can get a useful answer. And it kind've goes without saying, but you also need to ask your question to the right audience. Asking the right question to the wrong person or group will be as fruitless as asking a poorly formed question to a panel of experts. You know you haven't asked a very good question when you get a lot of questions back in return. You can tell a thoughtful question because it really gets to the core of the problem - most likely a result of a certain level of person's own study. They are learning, after all, and a certain amount of effort is expected - no pain, no gain, and all that. A good question also contains enough relevant surrounding details so that your audience can best answer - but not too many, "Just the fact, Mam."

Given those two qualities, there is very little you can't accomplish, no matter what tools you use.

So I personally think that if you stand back and look at who is doing the cool stuff, those people have those successful problem solving, can-do personalities. That is the "tool" that all the neat nifty projects have in common from autonomous helicopters to balancing robots to lawn mowing robots to ... just do a few Google searches and you'll find hundreds without trying too hard.

We like to say the project is successful because of this processor or that microcontroller or sensor X. I'm guilty of it too. I love a good project which showcases the capabilities of my boards. In a way, it's kind've a paternal feeling - something I made is doing this really amazing thing. But the reality is that it's the person or team behind the project that make it successful, not the processor or board. The microcontroller or board can make certain things easier, more reliable, faster, etc, but successful people and teams find ways to overcome those in spite of the limitations of their tools (and every tool has limitations). Look at the great architecture throughout the past few thousand years. Some amazing buildings and structures have been built with just the barest of tools and the crudest of materials - the Sistine Chapel, for example - truely works of art. Today, we have fantastically advanced tools and materials by comparison, yet it's rare to find a house that will last longer than the mortgage to pay it off. What does that tell you about gaging success by the tools? It's the people and their desire to accomplish their goal!

Good tools can make things easier, of course, though :-)

-Brian

Parallax is a well-established group; couldn't go too wrong. basicx.com supplies a similar chip that also works well.

Another source of useful electronics is

Lots of good stuff from processors to displays to wireless and sensors.

As far as processors go, ARM chips are generally faster than PICs, Stamps, or AVR; they're also 32 bits instead of 8. If you like a cookbook approach and want a large hobby community, stay with the simpler chips. If you want a serious processor and would like compiling with gcc, then give the ARM chips a look.

supplies numerous processor boards, but I've not purchased from them, so I can't vouch for their quality yet. TI has a nice set of DSP processors (e.g. the TMS320x2812 or the TMS320C6713), but their dev kits are generally expensive ($400+).

Later, Daniel

Hi Gordon,

I don't know if I should take that as a complement or not :).

All I can say is that I've been programing for about 20years on everything from Z80's and 6502's in assembler up to a large IBM host system (mainly SQL queries/reports) but I programm ATMELs for "fun".

I also see myself as a lurker in this news group :)

Regards Ian Dobson

Home of the Atmel based UDP mobile web cam

mails scanned with av-filter.pl (F-Prot / perl)

"Gord>> I would also recommend the atmel/bascom route. Being a compiled language >> you

I bought one of the Olimex boards from

I think they carry the entire Olimex line. I have no complaints about the quality of the board, but not much in the way of support is available. Several people in my local robotics club have purchased ARM boards from and been quite happy with them.

The downside to ARM chips is that the initial learning curve can be steep.

Jeff.

The biggest downside of the ARM chips IMO is that the development environments can be quite expensive. Even if you use GNU tools, you still have to program the chips. For that reason the "smaller" chips are a bit easier to bite off. The PIC and AVR are great, the AVR has the best advantage in that with the GNU-AVR tool chain you can get free open source stuff. The Atmel FAE's tell me that the GNU AVR compiler comes in a close second for code efficiency. Add that to the very inexpensive chip programmers and learning boards and it is a hard platform to turn down.

IMO, YMMV, DLC

Randy, I took a look at your site and am interested in your NMIH-0050 H-bridges.

What do you mean by "free wheeling diodes" ?

Thanks ! JCD

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The NMIH-0050 are very popular H-bridges. Does quite well up to 20KHz (by our testing and can even operate at 30KHz with some heating due to the high speed switching). Also it has good internal protection; undervoltage, over-current, thermal shutdown, etc. It will save itself if it can. You really have to slam it around to get it to overheat.

Free wheeling diodes mean the diodes built across the motor in reverse direction. There are four. One each goes from ground (anode) to motor terminal (cathode), and one each from motor terminal (anode) to +V (cathode). What these do is allow the back emf of the motor to be shunted off into the battery. You know, if you build up a field across an inductor (in this case the coil of the rotor/stator) and suddenly switch if off, as the field collapses, the energy has to go somewhere. The voltage will rise until a conduction path is found. On cheaper H-bridges, like the original L293 lower power H-bridge for example, this spike can wind up killing the output transistor. So you put external diodes across the transistor backwards. So as long as the voltage behave themselves and stay below the battery voltage, there's no problem. But if they should kick higher, they reverse bias the diodes and get dumped into the battery.

Found a write up on it here

you want to know more

-- Randy M. Dumse

Caution: Objects in mirror are more confused than they appear.

I'm new to all this and was studying your NMIH-0050 board and the schematic to try and understand how an H-Bridge works. Maybe some people here can educate me.

What stuck me as odd, was that was no input combination that would just allow the H-Bridge to turn off (i.e., all 4 transistors off). It must either be on, or in one of the two braking configurations. And then there was the suggestion that one typical way to drive it would be to simply alternate between forward and reverse in varying duty cycles to control the speed.

I understand how alternating between forward and brake, or forward and reverse would work nicely to control the speed, but my first thought was that it would be wasting a lot of energy and generating a lot of extra heat by doing that (instead of alternating say between forward and all off).

So, why is it done like that? Is it the nature of DC motors that they don't actually waste the energy when a forward spinning motor is put into reverse by the H-bridge? Does it instead (maybe with the help of the freewheeling diodes) actually just pump the energy back into the battery?

What would happen if you had an H-Bridge that could be turned off, and then alternated between forward and off to control the speed instead of forward and brake or forward and reverse? What would be the advantage or disadvantage of each of these three techniques in terms op all the relevant factors like torque or energy wasted etc?

And another related question. Do the free wheeling diodes effectively cause the H-Bridge to go into a brake mode if you turn all for transistors off (and it's connected to the battery to allow the energy to flow back into the battery)? In which case the actual brake mode of the H-Bridge is somewhat redundant and energy wasting since it short-circuits the motor and causes the energy to just turn to heat in the transistors and motor windings?

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Thanks ! That is very informative & a big help ! I will probably be snatching up a couple from you soon! JCD