A simple project board for the 08M

[bwevans]

A few of us were discussing using the PICAXE in various curricular activities. I agree that breadboards have their place and that wiring up an 08M is not the hardest thing in the world. With that said I wanted a way to give students an even easier route into controlling things with a micro. I took inspiration from the arduino - <A href='http://arduino.cc/' Target=_Blank>External Web Link</a> - which is hugely popular at the moment and in use by NYU and UCLA particularly in the arts &amp; design departments. Within no time at all students (and n00bs alike) can have their first hello world up and running and it also works well for more advanced applications like quickly hooking a flex sensor to a servo.

At 30$ and the more complicated language I felt the arduino could be improved upon, or at least made easier and simpler with the loss of as few capabilities as possible. So Ive been working on a small board for the 08M that could be offered in kit form (or pre-made if I could find a distributor willing) that has the serial plug built in, vreg wired up with a standard power jack, and easy access to the pinouts. I was going to wait until the prototype made it back from china to show everyone but then I found Eagle3D which is super cool so here you go:

<A href='http://www.csulb.edu/~bevans2/AXEbrd3Dblack480.jpg' Target=_Blank>External Web Link</a>

Pin0/Serial jumper at the top, LDO 5v vreg, 2.1mm power plug, can take as low as ~6v DC in, female pin headers for the pinouts (may use small screw terminals instead). You can easily wire up an LED to pin0, servo to pin4, and even an analog sensor without touching a breadboard. Overall dimensions are 1.25&quot; x 2&quot;.

Thoughts, criticisms, comments, opinions, drive by banana flinging... ?

Brian

 

[hippy]

Looks nice. Things off the top of my head, and I'll think more on it ...

A reverse polarity protection diode on Voltage In is a comfort, and as a half-wave rectifier usually allows AC as well as DC operation; even less to worry about when pulling walwarts out the junk box. Makes it near indestructible unless one finds a 40V PSU !

I always fit a power-on LED ( via 1K8 to keep current down ) and usually one across Serial Out / Pin 0 so I can see download is working, and it's an 'always there' LED to toggle to prove the PICAXE is working, and it also flashes on SERTXD.

A row of holes around the PICAXE is convenient for additional hookup wires, pull-ups for specific applications and somewhere to jam a meter / scope probe.

Shouldn't there be a 100nF-220nF decoupling cap somewhere ?

As all this adds components and cost, I'd suggest adding the tracks / holes and silk screen but leaving parts optional for people who might want them to buy and fit themselves.

 

[Rickharris]

Why go to 9 pin download when the jack socket is so cheap, keeps with the rev ed pattern and PDF files and works - also stops people using the download cable for anything else.

 

[Rickharris]

At school we use the Rev ed project PCB kit for the 08 and connecta set of solid core wires to it for connection to breadboard.

The entire thing with battery pack and bread board is glued onto a bit of MDF Students soon learn which wire does what, 20 boards

Works well as long as you have staff who are willing to take the time to learn how to use it - Another story!

 

[manuka]

<b>Arduino </b> , meaning &quot;Friend&quot; (Italian, Old German) &quot;Valuable friend&quot; or &quot;People's Friend&quot; certainly looks a tempting next step after wetting your feet with Picaxes. You'll have to convince us however that they'll seduce beginners over dirt cheap 3 x AA powered 08M driven breadboards! See the barebones approach that's very common for intro. NZ/Aus educational Picaxe work =&gt; <A href='http://www.picaxe.orcon.net.nz/bboview.jpg' Target=_Blank>External Web Link</a>

 

[Dippy]

I won't look, but I bet a fiver that it is a picture of a breadboard.

 

[Rickharris]

Put your money away Dippy (I looked) <img src="smile.gif" width=15 height=15 align=middle>

 

[RexLan]

I got the software and can't get it to work at all. Says no vector, no face , etc.

Instructions are lacking

 

[bwevans]

Arduino, also an old king of the city Ivrea, Italy. ;-)

Hippy, Im going to use the LM2940 for the vreg specifically because it has the reverse protection diode built in. It gets rid of an extra part that way. I dont know about hooking up AC but the 2940 is a nice bit of hardware. It also specified very specific caps to be used on the power lines... .47 incoming and 22uF outgoing IIRC. I wasnt sure about adding anything else. I wanted a power on LED but couldnt cram it in and so ultimately choose size over features. When/if I go to SMT Id like to get it in. As is you can add one on pin0 for the micro power on LED which I prefer if Ive got the i/o room.

I choose the DB9 b/c its bog standard and in many cases doesnt require extra investment. I had students put together project boxes which included a breadboard and a DB9 mounted to the outside and many of them just plugged this box right to the back of their laptops. (lots of college students have laptops) So in this case the board could plug right in (the size helps here) or youll be using USB to serial anyway and so have an adapter.

As for the breadboard... they will always be neccy for experimentation. These kits you guys use do work wonderfully if you care to hook them up yourself or are in a school situation where they are already prepped for students to pick up and and start programming. I had my students use Stans model for hooking everything up and it was tedious for the newcomer to do. Just watching them solder to a DB9 was painful. Then once everything is hooked up how many of you have dropped a breadboard and had everything come loose? Or you need a permanent application and have to perf board the same vreg/program circuit over and over.

So the idea was make it even simpler for the newcomer, take some of the repetitive work out of it and make it generally more approachable. (Under the particular assertion that the end user would have to make it themselves and not be provided with a pre-built box.) Then if you have a crazy circuit your building with multiple picaxes or something of the sort you can use this board almost as a programmer.

Ok breakfast is on the table. I know some of you I will never convince but I still appreciate your comments!

More thoughts?
Brian

 

[thelabwiz]

How much cheaper than the 08 protoboard from Peter Anderson? <A href='http://www.phanderson.com/picaxe/index.html' Target=_Blank>External Web Link</a>
With shipping and an 08M it's about $15US.

John

 

[manuka]

Splutter-DB9 =only 3 wires! I've just<b> DROP KICKED* </b> tested a Picaxe breadboard akin to =&gt;<A href='http://www.picaxe.orcon.net.nz/pik3.jpg ' Target=_Blank>External Web Link</a> &amp; nothing came adrift. In ~30 years of supervising students with BBs in fact I don't ever recall a dropped one suffering! Far more often parts will fall out of a stuffed PCB as it's turned over during hand soldering.

With every respect to Peter I have to say that his <A href='http://www.phanderson.com/picaxe/picaxe08m/picaxe08m_dev.html ' Target=_Blank>External Web Link</a> is harder to follow for newbies than our Kiwi versions. Aside from my increasingly infamous layout <A href='http://www.picaxe.orcon.net.nz/bboview.jpg ' Target=_Blank>External Web Link</a>, check Andrew's =&gt;<A href='http://www.picaxe08.orcon.net.nz/ ' Target=_Blank>External Web Link</a> &amp; note the <b>pre teen </b> kids using them.(As an aside, the booming NZ oil &amp; gas region Andrew is based in has an immense adult skills shortage, &amp; his &quot;Bright Spark&quot; schools work is part of a NZ govt. funded technical up skilling scheme. A large part of his work involves enthusing kids who may otherwise feel electronics is too hard. Check their smiles in the pix to see just how successful he is at this!)

Even THESE approaches daunt? Try Andrew's nail &amp; clip versions =&gt;<A href='http://www.brightsparks.org.nz/MentorFTP//PICAXE-08/www_help/Files/PICAXEtalk.jpg ' Target=_Blank>External Web Link</a>

I can not stress enough that<b> encouragement </b> (at least here in NZ/Australia) of today's cynical Ipod/PlayStation/Cell phone era youngsters is a crucial aspect of Picaxe promotional work we do. A culture that electronic gadgets are just disposable fun,linked with a perception that there's no money in electronic careers, means many youngsters just WILL NOT even bother checking the likes of battery voltages or broken wires. If such basic woes are perceived as too hard then indeed &quot;Why bother&quot; with more involved circuitry?

I seemingly speak of this endlessly, but those of you at the &quot;electrons in your blood&quot; level may not appreciate the nature of the quest for youthful &quot;hearts &amp; minds&quot;. Unlike my own -mumble- NASA/Apollo era youth,electronics would be the last career anyone with vision would now consider- here in NZ anyway. There's perceived to be more demand &amp; income (MUCH MORE !)in standard electrical work for starters. A 20yo. idealist also tellingly mentioned to me recently <i>&quot;I want to work in a field that gives satisfaction with a well made product lasting decades, NOT some hi tech gadget tossed away after a year ... </i> Stan

<b>*Footnote </b> : In a rugby playing country like NZ, the &quot;drop kick&quot; test is considered a fairly standard initial measure of project ruggedness.


Edited by - manuka on 06/01/2007 22:59:11

 

[tarzan]

&#8220;ultimately choose size over features&#8221;

My opinion this is a mistake. You should set a higher standard than what there is currently available. I would have provisions for DE9, 3.5mm stereo socket &amp; 3-way polarize header. Also add enhanced down load circuit and protection diode for input3 leg 4 of 08/08M Picaxe. You could also produce a plug-in/add-on PCB proto-type area. Make the orientation of the PCB and output header so as to easily plug into a breadboard without covering too much area of the breadboard. One way to achieve this is to use a 90-degree Molex header and stand your PCB on edge vertically then insert into breadboard. Or emulate this layout.<A href='http://www.parallax.com/detail.asp?product_id=32310' Target=_Blank>External Web Link</a>

Flashing LEDs always look good and are functional too.

My two cents worth.

Edited by - tarzan on 07/01/2007 01:48:10

 

[gidgee]

to each his own or what ever rocks your boat, all have a place in furthr learning of this great little chip
john

 

 

[hippy]

I hadn't twigged the LM2940 was anything but &quot;a regulator&quot; and it also appears to be designed for automotive applications.

I'm in favour of the DB9 and for those who already have 9-to-9/25 cables, it saves the cost of another. I use the 3-pin molex on most of my kit, and rejected using 3.5mm, especially as there are so many variants around ( for cameras, PDA's etc ) which often have different wiring, and there's that &quot;shorting output to 0V&quot; risk when inserting and removing.

From a manufacturer's perspective, not having to buy / supply 'specialist' cables nor force the user to buy from another source ( more P&amp;P, more aggro ) makes DB9 a logical choice.

 

[wilf_nv]

Your project is very interesting, using the picaxe as enabling technology for artists.

To make the technology factor less obtrusive, the whole package should have a natural, intuitive, even aesthetic feel to it. The picaxe approach of &quot;keep it simple&quot; makes the learning curve quite smooth. For minimal applications, the picaxe low startup cost, low system price and rapid design cycle time is hard to beat.

Having this forum as a resource makes it possible to quickly solve almost any problem, often with new innovative solutions that push the knowledge envelop and makes it all very exciting.

More to the point:

I have used the LM2940 myself for a number of projects. It is cheap, readily available and virtually indestructible.

But there are some subtle problems you should be aware of. The LM2940 has a quiescent current of 30mA which is high for battery powered applications and this current rises much higher when the input voltage approaches the output voltage typical of a low battery condition.
The datasheet skirts around this peaking of quiescent current, which is quiet, common for LDO regulators when the series regulator transistor is driven deep into saturation in order to maintain regulation

The 1A rating implies that you would use this regulator for a common supply for the picaxe and the load.

This is not recommended especially for heavy loads like hobby servos. Consider a split supply or at least an RC filter in series with the picaxe +V supply pin.

For low power battery or solar operated projects consider using the drop in LM2931- 5.0 (T0220), which can supply up to 100mA max but has a quiescent current of 500uA when the load current is less than 10mA as would be the case in the SLEEP mode. The LM2931 does require a 100uf output cap for stability but that would serve a LM2940 just as well.

There are CMOS LDO regulators which on paper outperform these bipolar LDOs but I have no experience with them.

Regarding the logistics of using your picaxe proto board in real applications:

The concept is a basic general-purpose picaxe uC only platform that should be foolproof and gets results quickly.
That's right in line with the whole bare chip picaxe concept.

At the same time there should be some protection on the inputs and outputs to limit current to avoid damaging the chip via external connections.

You can also look beyond simple projects to applications in which your basic platform may be connected to I/O expansion boards designed for more demanding tasks.

A common form factor with some kind of standard connector, header or expansion bus would allow the basic board and specialized I/O boards for interfacing with popular sensors and actuators to plug together or be connected together with short flat cables using headers and IDC connectors.

Not a trivial task to standardize anything but I would love to hear what kind of interfaces are commonly required for art installations, animatronics etc.

In the area of distinct art applications software, a library of modular program blocks developed to support commonly used sensors and actuators that can be smoothly combined in many ways, may provide both structure and flexibility, a light framework on which creative ideas can be quickly tested.

Although just a small chip in the scheme of things, mixed into the steaming broth of hardware, software and wetware, who knows what wicked new picaxe ideas may this way come.

wilf


Edited by - wilf_nv on 07/01/2007 18:55:55

 

[premelec]

Stan, I used to have a breadboard with springs for connector points - you pulled a bit on the spring to open it and stuffed in the wire and let the spring grab it or any of a number of other wires to the same point. I hope you'll put up a gallery of all these different methods in one place - what about twisted wire nuts? aren't we all?

 

[hippy]

That spring / peg-board was what got me into electronics in the early 1970's when I bought one from a school bring-and-buy sale.

Happy memories ... http://www.hansotten.com/philipsee8.html

 

[Rickharris]

double post

Edited by - rickharris on 07/01/2007 21:01:25

 

[Rickharris]

The phillips electronic engineer - thats how I got into electronics as well

Picture here <A href='http://images.google.com/imgres?imgurl=http://www.nzeldes.com/Miscellany/images/Homebrew08_medium.jpg&amp;imgrefurl=http://www.nzeldes.com/Miscellany/Homebrew.htm&amp;h=296&amp;w=295&amp;sz=51&amp;hl=en&amp;start=1&amp;tbnid=Q5fYV1IzDgrE-M:&amp;tbnh=116&amp;tbnw=116&amp;prev=/images%3Fq%3Dphillips%2Belectronic%2Bengineer%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DG' Target=_Blank>External Web Link</a>


You can also make a board with golf tee sized holes. Put a brass eyelet in each hole and you can use them to connect components using a golf tee to hold them in place.

 

[premelec]

Oh I love it! so many ways to make flaky connections to tech us how to troubleshoot!
OK that was supposed to be TEACH us how... but what the heck...

Edited by - premelec on 08/01/2007 03:04:04

 

[bwevans]

Just a few random things to add to the discussion. And thank you wilf for the comments.

Standardization and the art/design fields dont often get along. Which is why this board is simple and is meant to be an open ended stand alone object. Simplify the most common aspects of the PICAXE and leave the rest up in the air. I had thought a shield like idea used by the arduino crowd <A href='http://www.sparkfun.com/commerce/product_info.php?products_id=7914' Target=_Blank>External Web Link</a> might be nice but I havent thought much more about it. It could plug directly into the female pin headers.

Most things I do, been hired to build, or have coming from my students are concept driven, &quot;I want this to do that...&quot;, and the right hardware/software is found to match. This is as opposed to technically driven, &quot;I have this that will do that...&quot;, where the particular technology becomes the starting point and what it does or why it does it is secondary.

To this extent I used the text Physical Computing <A href='http://www.amazon.com/Physical-Computing-Sensing-Controlling-Computers/dp/159200346X/sr=8-1/qid=1168223321/ref=pd_bbs_sr_1/104-4649434-9710364?ie=UTF8&amp;s=books' Target=_Blank>External Web Link</a> written by a couple of guys from NYU that provided the students with a basic electronics overview followed by the basics of micros followed by a long laundry list of &quot;if you need to do this you can use this&quot;. The problems were their code examples which tried to take a broad approach of code for the BS2, BX24, and PIC and left us, using the PICAXE, out. (More or less.) This was confusing, so I had to write my own list of things that the student can use at whim. Reading switches, pots, flex sensors, cds, sonar, output to servos, hbridges, MOSFETs, relays, with various code techniques for randomization, variables, edge detection, and so on. The idea as wilf suggested is that of software/schematic building blocks that they could combine to get what they needed done. The more they work with it they more they pick up through attrition. At some point I may have to write something more inclusive for this class of mine that takes the best of Igoes's book with the best of the PICAXE manual and see where it goes.

At least in my case, which is this boards primary purpose, the board was never meant to be a be-all-end-all gadget. This scares me: <A href='http://www.makezine.com/controller/' Target=_Blank>External Web Link</a> Its intimidating. Sure my board could have so much more but the coolest thing about the 08m is in its combining power with pure simplicity. If the chip unleashes its holy smoke its only $3 to drop in a new one.

This project board is not for robotics (although a lot of my own work might get labeled with that) or otherwise highly complicated projects and so doeesnt need much in the way of i/o and more importantly 98% of these types of projects have to run unattended for maybe a month or longer. So simplicity and mains power is a must.

As for the power.... it is meant to allow for a max 1 servo with little other load. This may not be the best habit but helps for simple experimentation and prototyping. Otherwise there is a pinout for unregulated voltage so a 7v adapter could be used and servos could be attached to the Vin pin instead of the regulated +5V pin. I prefer the students to use 12v ac adapters so they can use relays, solenoids, motors, etc so having a vreg that can source an occasional servo is helpful. I have also looked at the LM1086 as an alternative and may at some point develop a SMT version of the board which will open other alternatives.

Blah.. I write too much. Thanks for all the comments though.
Brian

 

[hippy]

One thing to keep in mind is, that with the success of you 08/M board, students / artists will soon start asking if they can have more I/O and/or more lines of code, which points to an 18/A/X board on the horizon.

It may be worthwhile looking at the design of such a board now in parallel with the 08/M. It's nice to produce a unified product range with common functionality. If you fit a power LED on the 18, someone will complain there isn't one on the 08/M, or that you should leave it off the 18 to make the board cheaper !

Particularly if you are going for 'shield' / pig-tail adapters, it would be nice if they could plug into either board, and it might be worth looking at how to do that before finding you do have some incompatibility issues.

 

[Wrenow]

I am in agreement with Hippy on the 18x board being co-developed is a great idea. I love the 08M, but am running into some &quot;number of pins&quot; issues myself (want to read 3 hobby R/C RX servo control pin signals, do some logic and math, and output 1 or preferrrably 2 servo outputs on one of my projects; 3 analog inputs and one or two digital inputs, 2 or 3 servo outputs - maybe as many as 4 - and a digital output or so on another), so am trying out the 18X on the problems. Just breadboarded and fired it up tonight, now to modify the software, attach the inputs and outputs, and play. May end still end up with the 08M in the final applications, though one would require two independent 08Ms (would sure like to).

Wreno

 

[bwevans]

I like that idea. It would be nice to have that in the stable so to speak for when those instances happen. My only problem with the 18x chip is that you are still stuck with only 1 PWM. My students had numerous projects where they would have the need for 3 or 4 PWM outputs and so would have these crazy breadboards crammed with 08ms. Anyway...

What about the through hole components on the board? I had considered making the move to SMT parts, at least for resistors, caps, etc which may allow me to get the power ok led, have an enhanced d/l circuit, and if I make an 18x version will be able to fit that in without increasing the board size by to much of an extreme. Problem is I had wanted this to initially be offered as a kit since Im not sure how to go about getting these produced otherwise. The SMT version Im afraid would be too hard for the even college-level beginner to assemble themselves. (Hence making my 'simple i/o board' rather complicated.) Thoughts?

Brian

 

[slurp]

I'm just about to have my first go at SMT, the board is home etched using a laser printed mask. I've used this process with thru' hole designs in the past but this should offer a great reduction on drilling.

Over Christmas I've been doing some temperature measurements on the ceramic hot plate in the kitchen. I'm fairly confident that I can get close enough to the required temperature profile file. I plan to use the syringe dispensed solder paste and a good pair of tweezers.

For what it's worth I think the board looks good but would go with the more I/O vote

Also like the double sided connection that www.ladyada.net use on their miniPOV3 kit. There is a picture here <A href='http://www.ladyada.net/flickr-cache//172846883.jpg' Target=_Blank>External Web Link</a>

Not so easy with a home made board but the double sided isn't a problem otherwise.

Best regards,
Colin


 

 

[hippy]

It's not just assembly but removal and repair if the PICAXE gets damaged, and its always nice to be able to swap between 08 and 08M, 18/18A/18X.

I've not done any SMT and not sure my eyes are up to it, and if I did it would probably be to fit to a board I can plug into a DIL socket !

A compromise could be SMT, with the holes and clearances for a DIL socket if SMT removed. It would reduce your space saving a bit but there's no reason components cannot be put under where the DIL would go. As long as the legs go in the holes and can be soldered it doesn't need to be flush; may look messy but works. The holes for the DIL sockets can also be used for wire hook-up points if using the SMT.

 

[Dippy]

I like the concept, would it be a major job to have a DIL socket to take 08M or 18X with some jumpers??

SMT obv has size advantages and you can get SMT DIL/DIP ic sockets, but I guess it depends on your target? One-or-two offs in the kitchen or selling to a mass market? Assembling a properly made s/r smt pcb (in ones or twos) isn't too painful with a soldering iron if you use pukka solder paste, but for proper manufacture you'd have to produce quite a few completed boards for a good unit cost. And if it were 50p too much then people won't buy - you know what they're like. Some people would spend weeks scavenging and drive 500 miles to save 10p.e.g. My Dad.

As you have seen from the postings you'll have a tough task getting one-size-fits-all. Otherwise you could end up making a full blown eval board.

Couple of years ago I was dabbling with 'stampifying' an smt 18X onto an smt 0.6&quot; pitch DIL board with 5V reg and enhanced I/f. I did the artwork to produce a similarish pinout to Stamp2 but that was all. Seemed like a good idea at the time...

Anyway, take some of the good ideas on board, make one or two, and then do a costing.

 

[Tricky Dicky]

I developed 2 protoboards for my students which simply plug into the breadboard. The 08M version simply contains the download socket and resistors, terminal blocks for connecting inputs and outputs and 3 switches to switch over the combined input/output pins. The Picaxe 18 version is similar but includes a reset switch.

I find it works well for my students as it takes out all the hassle of building a standard setup but allows them the freedom to construct their own input and output circuits on the remainder of the breadboard.

See an example of a 08M based IR transmitter and reciever<A href='http://picasaweb.google.co.uk/Tricky.Dicky51/Picaxe02/photo?authkey=pSjNYDidzto#5017782438004240834' Target=_Blank>External Web Link</a>

If anyone is interested in either I can e-mail the PCB masks in either PCB Wizard files or Circuit Wizard files.

Richrd

 

 

[bwevans]

Well I dont think Id go with an SMT version of the 08/18 itself in this application because blowing the micro does happen occasionally. Just thought that if everything else was it would keep things small but with small comes complexity. Although I have been approached by the chair of the Jewelry department about developing a wearable electronic art sort of course. I thought the perfect board for that would be stamp sized that had an SMT 08m with onboard USB and micro A USB connector. That way the 08m could be powered from USB or some small li-poly source and interface to sensors or small motors. I dont know, thats still a way off if it ever happens.

Not to keep beating the arduino horse but they managed a stamp sized version of the ATmega168 - <A href='http://www.arduino.cc/en/Main/ArduinoBoardMini' Target=_Blank>External Web Link</a>.

Speaking of prototyping, Spark Fun has an amusing article up about prototyping and many of their horrendous mistakes over the years. One lesson learned: keep it simple!

Brian

 

[bwevans]

Well I dont think Id go with an SMT version of the 08/18 itself in this application because blowing the micro does happen occasionally. Just thought that if everything else was it would keep things small but with small comes complexity. Although I have been approached by the chair of the Jewelry department about developing a wearable electronic art sort of course. I thought the perfect board for that would be stamp sized that had an SMT 08m with onboard USB and micro A USB connector. That way the 08m could be powered from USB or some small li-poly source and interface to sensors or small motors. I dont know, thats still a way off if it ever happens.

Not to keep beating the arduino horse but they managed a stamp sized version of the ATmega168 - <A href='http://www.arduino.cc/en/Main/ArduinoBoardMini' Target=_Blank>External Web Link</a>.

Speaking of prototyping, Spark Fun has an amusing article up about prototyping and many of their horrendous mistakes over the years. One lesson learned: keep it simple!

Brian