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31  Using Arduino / Project Guidance / Re: Workshopping £1.40 Arduino-Compatible (£3.05 including USB!) on: September 05, 2012, 12:51:46 pm
Latest developments now mean we can make the components for an Arduino-compatible circuit available to Morecambe hackers for around £1.40 in component costs, or £3.05 including the CP2102 USB to UART adapter.

This is a fairly major development, putting a binary-compatible #Shrimp about one tenth of the cost of a retail Arduino!

I'll change the thread title to reflect this. To find out more, visit
32  Using Arduino / Project Guidance / Re: Workshopping minimal stripboard £4 USB-Connected Arduino-Compatible on: September 04, 2012, 06:11:51 am
An update on the Laptop Shrimping project. We now have a URL at and Twitter @ShrimpingIt

The #Shrimp design is fairly stable now thanks to many contributions from people who know stuff.

I've personally distributed about 30 kits of parts. Some are taken with a breadboard, some with USB-UART adaptor, and some taken by hobbyists to put onto stripboard at home. However, the most exciting direction is feeding in to the National Curriculum and STEM subjects here in the UK.

Thanks to @teknoteacher for making me realise something like the #Shrimp was needed at Hackademy "Inside the Machine" Thanks to @oomlout for early discussions and support and thanks to @tshannon for hosting and supporting Shrimp makers at Howduino. Thanks to @jonachamberlain @patlink72 @iMartyn and his Mum for testing out the first boards and working with me to think of decent expansion kits. Thanks to Mike Cook for all his experimentation with a clone of the MB Games 'Simon'.  Thanks to @monsonite and @simonmonk2 for suggestions. Thanks to many many others  including those in this thread. Sorry if you've helped I didn't credit you by name but I've had a huge amount of fun and engagement with loads of people.

There's a lot of excitement about being able to actually solder together your own Arduino-compatible. Thanks to Fignition, and @ManchesterBudo for helping me realise how important this is to people - it's now become central to the project.

Essentially, this is developing into a classroom pack which teachers should be able to progressively introduce to pupils, with a single lesson to build the circuit and program it on breadboard, another lesson to prototype established project designs from 'expander' kits (which include some extra sensors and actuators for a specific project), and a final lesson to solder onto stripboard and test on battery. At any point, it is feasible for individuals to take a direction towards their own personal project/invention/game/alarm/joke/toy what have you. We're just offering a kind of template for leading people through this.

All along the way, you're working directly with incredibly cheap components and using the same 'mental model' from the moment you start building your Arduino-compatible, right the way through to prototyping your own project circuitry - one advantage of not using the blue board, at least for education purposes. There's a huge crossover with Design and Technology subjects, and it's loads of fun designing, choosing and packaging glossy buttons, displays etc. even for those who don't want to change the circuit or the program.

Here in Morecambe the rough plan is to make the components for a Shrimp available for £3 at workshops, with a returnable deposit of £2 for the USB-UART adaptor (which you may not need when you've finished building your project), and a returnable deposit of £3 for the breadboard (which you can give up when you've finished prototyping and you've transferred to stripboard, or maybe you found a cheaper breadboard smiley

Hopefully people will get involved enough that they want to keep both the CP2102 and the Breadboard for further projects, and we can keep giving them packs of £3 components for each new experiment they undertake, with the aim that they actually deploy their experiments, powered by battery or a USB power source (without UART), and don't deconstruct them again as people like me tend to do with Arduino because of owning a limited number of boards.

Anyway, it's been a bit whirlwind. The moment I get any parts, people seem to take them away, so I've bought another load of 100 lots from mouser/tayda/shcfstore (the cheapest places I've found to get the bits so far). The CP2102s could take a while to arrive, unfortunately, but I'll have all the other parts within a week.

We can help you get the parts at a reasonable rate, and with rapid shipping from UK but we are not claiming any ownership of the design, though it's nice to get credit and pingbacks.

If you're interested in following along, getting a kit of parts or contributing to the project, then get in touch @ShrimpingIt
33  Community / Website and Forum / Licensing/Permission for Images on the site on: August 28, 2012, 05:57:07 am
I'd like to be able to use the Pinout image at... part of material which I'll distribute at a workshop and may share online.

The same is true of e.g. the images including the Fritzing breadboard view, and schematics. When I'm introducing and commenting on these individual experiments within workshops, I'd like to have freedom to use the images, rather than having to remake them from scratch for each experiment I include.

Is there a general principle regarding licensing of images, for example those in the Wiki? Everything says copyright Arduino at the bottom of the page. Who do I need to seek permission from?

34  Using Arduino / Project Guidance / Re: Running Arduino-compatible from batter(y|ies) without regulator on: August 27, 2012, 10:33:23 am
LiPo are more like 4.2V when fully charged and 3.7V when discharged.
If you running at 16MHz, then full performance is guaranteed down to ~3.8V.
If you run at 8 MHz, it's less. So you coul run from a LiPo directly and not use a regulator at all.
I have an RF remote control that does just that - 8 MHz, 1000mAH LiPo, MAX1811 to control recharging the battery from a 5V source.

I am testing a '2560 design right now using 3 AA batteries. I have a 24V to 5V DC/DC module on the board, but don't have the right female cables yet to power it up.
Running from battery with no regulator is fine as long as the battery voltage is in the correct range.

Setting fuses is a really hard ask for new Arduino-compatible experimenters in a workshop. Do you know, is attaching an 8MHz crystal like in the place of the 16MHz crystal more-or-less equivalent to asking it to use it's internal clock, or is the change of fuses also needed to get other aspects of 328 behaviour to line up correctly with the 8MHz clock speed?

It would be great if I could just plug in an 8MHz crystal to the circuit, then use a 'board' setting in the Arduino IDE which would assume an 8MHz clock in its defines for Serial interrupts etc. Then I could use that setting when programming a simple 8MHz ATMEGA328 circuit which could be programmed directly off 5V but run down to a <3.8V supply on a battery without changing anything (assuming the project doesn't mind timings all going astray as per PaulS' comments).
35  Using Arduino / Project Guidance / Re: Running Arduino-compatible from batter(y|ies) without regulator on: August 27, 2012, 10:21:57 am
Update: given the comments by WizenedEE below, I'm now of the feeling I shouldn't have accepted all of PaulS suggestions entirely as the gospel truth, although it sounds intuitively to make sense that many things change with a change in voltage, it seems that there are mechanisms specified to prevent this, such as crystals, and that there's no need to change fuses necessarily for a change in voltage. There still seems to some debate anyway. Now go on to read my original response >>>>>>>>>

With suitable changes to fuse settings, the Arduino can run at either 3.3V or 5V, not any random value in between.

Aha, makes perfect sense. I had no idea that fuses had to be changed to support a 3.3V set up, although I knew 8MHz operation needed a change in fuses I didn't figure for the voltage itself having to be accounted for. I guess the Jeenodes I had just came with the correct fuse settings out of the box. I'll follow up with JCW at Jeenodes and see if I can find out more about this compromise.

...bad things happen when the voltage is not constant. Serial data transmission, among other things relies on clock speed, which is a function of voltage.

Right, that makes a huge amount of sense too. Fortunately when we're connected to the USB (and wanting to attempt Serial comms) it will be powered off the 5V regulated. The rest of the time perhaps we'll get away with a slow clock (and incorrect timings). Once people have got the idea of programming simple behaviours and the arduino-compatible bug has bitten, we can expose them to more complex design issues, so when they start to design their own projects which demand a near-real-time clock or an actual real-time clock, then we can talk them through using a power regulator or a supporting chip. I think we're already stuck with a 'now we add 4 capacitors and a diode for protection' phase in the workshop, and this might be a moment to introduce the power regulator too.

Perhaps you're trying to underline my ignorance.
Not really. Just questioning why you think that the 5V is not important.

I simply didn't know why 5V was important. What you describe makes a lot of sense, thankyou.
36  Using Arduino / Project Guidance / Re: Running Arduino-compatible from batter(y|ies) without regulator on: August 27, 2012, 08:11:59 am
Given their low cost I'd really REALLY consider using an LDO regulator when running from batteries. I wouldn't feel comfortable feeding any microcontroller-based project from an unregulated supply, even from batteries. It doesn't really add much complexity to the circuit smiley

One of the aspects of the way we're workshopping with the ATMEGA chips is to try and maintain continuity as much as possible from one stage to the next. Ideally the exact same solderless breadboard circuit powered off the CP2102 attached to a laptop is transferred to stripboard wholesale, without having to rethink or rewire it. One way to go is to include the LDO regulator in the circuit even when it's not strictly needed (e.g. when attached to the regulated USB supply). That way we can switch seamlessly from the USB-connected lab-prototyping mode into a battery-operated in-the-field mode without any sleight of hand.

Do you think this would work? I gather there's a loss of voltage when going through a regulator, but given the spec of the component you described this may not be significant.
37  Using Arduino / Project Guidance / Re: Running Arduino-compatible from batter(y|ies) without regulator on: August 27, 2012, 08:06:51 am
or that 5V is important for some reason.
You are trying to imply that it isn't?

Given Jeenodes are running at 3.3v and regular Arduinos at 5V I had the impression that the voltage could be anywhere in the range from 3.3v to 5v and from the thread I linked to, perhaps even a wider range than this. Perhaps you're alluding to something bad which happens when the supply voltage changes while a sketch is running. Perhaps you're trying to underline my ignorance. I'm a bit confused by your question.

I don't think the exact voltage matters for us, so long as the microcontroller is running stable.
There is a big difference between exact voltage and consistent voltage. Batteries will give you neither.

It may not be clear from my wording, but these are unknowns for me - my main reason to raise it on the forum. If you know a reason why regulating the power supply to 5V IS important, please share. Equally if you have notions of 'exact' and 'consistent' for voltage which corresponds with the well-functioning of ATMEGA328 projects when powered by batteries, then I'm all ears. The insights promised by your post could mean I have no choice but to include a regulator. However, I don't think I can guess what those insights are, yet.
38  Using Arduino / Project Guidance / Running Arduino-compatible from batter(y|ies) without regulator on: August 27, 2012, 06:38:21 am
I'm wondering what's the simplest and possibly cheapest portable power arrangement to keep an ATMega328P-PU or ATMega328-PU alive.

There are plenty of approaches involving a power regulator (and a power source > 5v) or a boost regulator (and a power source < 5v). However, I'm wondering if it's possible to simply power a 328 directly off some kind of battery technology which produces a voltage within the right sort of range, to maximise simplicity and minimise cost of tutorials and demonstrations.

So far I've been speculating about...
  • 3 AA NIMh batteries, coming in at about 3.6V 4.2V when fully charged
  • 1 Lipo battery, about 3.7V when fully charged
...but there may be other arrangements I should consider or concerns I should have.

I can't find a pre-existing discussion about this as I think most projects assume they are using a full-fledged Arduino including a regulator, or that 5V is important for some reason. Anyone have experience of running off batteries without any regulator?

In our case we're relying on Arduino-compatibility, but we're building simple ATMEGA328-based projects direct on stripboard, like this... the minimum component count and most consistency between running off USB and running portable the better. I don't think the exact voltage matters for us, so long as the microcontroller is running stable.

When any battery technology starts to go flat, I guess we'll need a 328P with picopower to handle a graceful brownout, though. Don't know what the consequences would be of using the simpler 328 without picopower on a battery-driven project. Perhaps it could corrupt the bootloader when it starts to run random instructions?

Update: I finally found this thread but seems to be inconclusive, with Jeenode offered as an example of running at 16MHz with low voltage and some saying chips will happily run down to 2.5 volts, whilst others saying it won't work.
39  Using Arduino / Project Guidance / Re: Workshopping minimal stripboard £4 USB-Connected Arduino-Compatible on: August 26, 2012, 11:53:51 am
Actually, I got the diode backwards - should be anode to Reset, Cathode to Power. I'll fix my earlier post.

That makes loads more sense, thankyou. Based on the original description I figured it could only be doing something useful via reverse breakdown.

Want any spikes on the Reset line dissipated to the power line.
Diode like 1N4148 will do.

Great, I have all the relevant info to order stuff now.

The 10uF Electrolytic (usually aluminum electrolytic) helps with any  big current ripples, while the 100nF help with higher frequency stuff and short term current demands.

OK, so I still need both.

Within the workshop I think I'll introduce a functioning (programmable) circuit without all the extra components, (just flashing a LED), then later (and before transfer to stripboard or working with servos etc) introduce all the protective components (caps and diodes) with an explanation of various forms of noise spikes, transient load and ESD which are likely when deploying in the field.

Hopefully then the extra 5 components won't freak people out too much when introduced under the heading of 'protection'. My aim is to have as little 'black magic' in the design as possible - the one perceived weakness of the nice shiny blue boards is that they are beyond novices to interpret and understand, compared to something you've wired yourself smiley

You don't have any extras to remove. The last diode & cap get you up to the minimum for an Arduino.

Hurrah. Time to crack open a celebratory beverage (6pm here in UK).
40  Using Arduino / Project Guidance / Re: Workshopping minimal stripboard £4 USB-Connected Arduino-Compatible on: August 26, 2012, 11:09:06 am
You should add a diode across the 10K resistor, Anode to power and Cathode to Reset, will keep the chip from attempting to go into High Voltage programming mode

Will any diode do for this job, or is it important to have a specific breakdown voltage? An ESD diode is mentioned, but I gather this is a description of its role rather than a type. I'm wondering about a 5.1V Zener diode wired in the direction you describe. Does that sound sensible? Here's a link to a possible part for the job...

I've not found the cap to ground to be needed. Likely the DTR cap makes it stable enough.

Initially I couldn't figure out which cap you found wasn't needed, but looking at the datasheet in more detail I can see figure 3.1 with a recommended circuit including the suggested diode and an extra cap. I think you're saying leave out the extra cap from their circuit as it's not needed.

Also put a 100nF cap from Aref to Gnd, will be needed for stability if one is doing any analog measurements.

I'll add this one.

I find I'm adding a lot of extras, now. Are there any bits I can sensibly remove from the circuit as it stands for a general purpose Arduino compatible? Especially wondering about the 10microFarad electrostatic from VCC->GND. I'm a bit vague about the circumstances under which it would do me any good, given there are already 100nF caps placed between VCC-GND and AVCC-AGND.
41  Using Arduino / Project Guidance / Re: Workshopping minimal stripboard £4 USB-Connected Arduino-Compatible on: August 26, 2012, 09:13:16 am
OK, eventually I noticed the Electrolytic capacitor was in the 'exploding' configuration. I've been post-processing the Fritzing diagrams in Inkscape to make the layouts more palatable, and had re-introduced an error. The Fritzing reference should be right, though.
42  Using Arduino / Project Guidance / Re: Workshopping minimal stripboard £4 USB-Connected Arduino-Compatible on: August 26, 2012, 05:40:32 am
I've updated the design to accommodate for...

  • The fact I can now get 16MHz Crystal and two 22pF Capacitors cheaper than a Ceramic resonator from Tayda Electronics
  • A perceived need for both rapid response and high capacity decoupling leading to 3 decoupling capacitors - from discussion with others, but could be overkill, so any other ideas are useful

The main benefit of this "Shrimp" design is the ease of transfer for those workshopping with 'Arduino compatibles' taking projects from breadboard-with-jumpers, through breadboard-with-length-cut-wires-and-components, to neat stripboard, meaning you can go from tabletop prototyping into something more robust without changing the circuit at all. This is something I hope will help delegates to the workshops.

I'm passing on the parts for these kits (including USB connectivity) for £5 now, which also covers my postage and handling costs. If you were to source these yourself, buying in the largest bulk volumes available, and barring postage costs (which tend to zero when you buy a million), you could make up Arduino-compatible component kits (including USB connectivity) for around £3.50

Get in touch if you're interested in sourcing these component kits for community workshops and I'll look into setting up something via eBay.

Now I need plenty of ideas for 'extension' kits which will be sets of components and code which permit the shrimp to be made into different things, like a "Milton Bradley" Simon game, a toilet-seat-not-down alarm, a Stylophone, and so on. Ideally only a couple of quid for parts for each extension kit. Really keen to see if this can help with the UK's transformation of it's ICT curriculum away from Microsoft and towards actual Programming.

Welcome your feedback. 
43  Using Arduino / Project Guidance / Re: Workshopping minimal stripboard £4 USB-Connected Arduino-Compatible on: July 04, 2012, 07:06:55 pm
Thanks for the heads-up, Crossroads. As mentioned earlier we're using a CP2102 in the place of an FTDI to save on cost. I don't know if the same is true of the CP2102. I'm using FTDI in the Fritzing diagram because the parts editor seems to be so buggy and problematic. At some point I'll have to edit a CP2102 part from scratch to make this diagram more accurate.
44  Using Arduino / Project Guidance / Re: Workshopping minimal stripboard £4 USB-Connected Arduino-Compatible on: July 03, 2012, 04:33:23 pm
For all those watching this thread, (especially following my presentation at Preston Raspberry Jam yesterday), I will be keeping the latest best-known circuit layout up to date following what is learned through experiments and workshopping at the URLs below. Those logged into the forum will be able to see the latest layout at the time of writing as an attachment below this post. Visit the Laptop Shrimping project to keep up to date with laptop scrimping, pimping and general hacking exploits, such as this article just published on the Safari Books blog.

Stripboard layout
Fritzing file

45  Using Arduino / Project Guidance / Re: Best arduino for servos/sensors controlled via web? on: June 26, 2012, 04:11:23 am
Surprised that no-one mentioned Jeenodes. These are Arduino-compatible devices including RF12 wireless available for the price of an official Arduino board, currently 18 Euros 50 Cents

Basically with one of these attached to the controlling computer, (you can use a CP2102 for this), and another one running the servos, you've nailed the wireless-remote-controllable servo spec for a fraction of the price.

Also Jean-Claude Wippler (who creates and ships them) is incredibly helpful and could probably walk you through the minimum you need to get going if you send him a question.

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