Safe use of the Arduino module

Hello,

I plan to experiment with the Arduino module, and give the kids as much freedom as possible. They don’t have the Arduino programming skills, so that will be hopefully fixed with a custom Scratch extension.

I just wanted to know if there is any guide what NOT to do - since there are many possible ways how to fry an Arduino board, I assume the littleBits version of the board is somewhat protected. For example, if a pin is declared as an output pin, then receiving some voltage in that pin can hurt the electronics. The docs say that there are three input and three output ports. Does that mean they can’t be declared otherwise?

I am somewhat confused about how to power, ground and data terminals are connected to the board. For example, powering of the Arduino module. Since the USB cable provides only data connectivity, I assume the ground and power terminals of the three input ports are all all interlinked and once the battery is connected to any of the input ports, the board powers up (and runs the setup() firmware). What if there would be two batteries connected to any two input ports? If the power is connected to Arduino module via dimmer, must the other dimmer connected to other port also be powered? Those questions would be clear if the schematics for the Arduino board and the bits be available - without the nice, kid-friendly just-click-them-all-in-one-chain abstraction peeled away.

The +5Volt of all the bitsnaps are connected together and all the GND (0volt) pins of all the bitsnaps are connected together.
The Arduino module is powered using the bitsnaps. It needs a good battery, I like to use a wire split between the power bit and the Arduino with both ‘output’ end going to inputs on the Arduino, that way you can disconnect a bit on the input side without interrupting the power to the Arduino. When the Arduino establishes the USB serial port, power cycling the Arduino can make the USB serial interface change. This can cause a lot of confusion when suddenly you cannot upload to it.
Modules that have an Input bitsnap usually require that the data wire be connected to something. A power bit has the data wire connected to the +5volt pin. So if the input of a dimmer is a power bit it acts as a variable voltage source.

Thanks, @codewizard58 those are some very good points.

I’ve found the schematic for the dimmer module, and was quite surprised about its complexity. All those extra diodes, I’m not so fluent in electronics to see why those are added to the core piece, the rheostat.

But surely, if an import port would be declared as output and one would connect the dimmer to it, then it could fry the Arduino, if the dimmer is at it’s lowest resistance? Or this particular implementation of Arduino just does not let those three ports to be declared as anything else than inputs.

With LittleBits you can still short out the data line and the power supply. It is not 100% unbreakable. Some components I use have iron cored wires and they like to try and short out the bit snaps. So far no actual damage.

Hi @Passiday,
You are right about frying your arduino when you switch 5 volt on a pin when this pin is defined as an output pin.
On the arduino website www.arduino.cc it is mentioned under the definition of output:
" Pins configured as outputs can be damaged or destroyed if they are connected to either the ground or positive power rails."
So the best way to keep your arduino bit alive is using the D0, A0 and A1 pins only as input and the D1, D5 and D9 pins only as outputs and never change this in the software…
Then due to the mechanical differences with the magnetized connections it can never go wrong…

Hi @Passiday and @codewizard58,
This is a forum thread about how inputs and outputs work on your arduino…
In here is a link somewhere to “10 ways to fry your arduino”… (from manitou)
http://www.ruggedcircuits.com/10-ways-to-destroy-an-arduino/

Thanks, @alexpikkert, for the insight. It’s better to keep safe with 3 IN + 3 OUT, in the class experiments. If they want to upgrade to more advanced experiments with more inputs and/or outputs, then they should be aware about the dire consequences and perhaps do it at their own risk and expense. And, after all, 3 ins + 3 outs is not that bad.

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Hi there! This is a perfect situation for a new tool for rapid electronics prototyping found here: www.aemachines.io. Just make sure you have the littleBits board selected and your kids can program at will, using graphical blocks in the Software Design area, and an assembly guide that is generated automatically in the Hardware Design area. You’ll have to add an email address to use the tool, but it’s free! (Account support coming soon.)

Hi @aemachines,

Even the preview link wants to harvest my email before showing me what you’ve got. Unfortunately I won’t sign up just to look at your products. How about putting more information on your landing page?

Hi @chris101,

Fair enough! We are adding account support soon. Then you’ll be able to preview the tool without providing any info.

We’ll post here again – or check back in a week or so!

Amy