Here is a question related to Electrostatic Discharge, sensors, and wool (there is also some cotton, bamboo-polyester, and plastic) in an Arduino project
Let me preface this by saying I am new to electronics, Arduino, and this forum, so please forgive anything that needs forgiving in terms of wording, posting to the right place, etc.
I am using about 12 Arduino Uno’s in a large sculptural-felted installation project. I successfully soldered Adafruit “Music Maker” mp3 shields (link: Adafruit Music Maker MP3 Shield for Arduino w/3W Stereo Amp [v1.0] : ID 1788 : $34.95 : Adafruit Industries, Unique & fun DIY electronics and kits) to these devices, and hooked up ultrasonic sensors to them. With some coding assistance from a friend, the sensors can now trigger multiple mp3 files. All was running smoothly, until yesterday. We began to install these electronics into these large felted (made from wool) sculptures, and the sensors seem to be less accurate than before. Whats more, every time a piece of felted wool is put in front of the speaker-cone (where the sounds play from), it makes a fuzzy sound, like the wool is causing feedback (the sound stops after about 3 seconds if the wool is held there). Then I had that sinking feeling of a huge oversight: wool (and other fabrics)+ a dry environment +electronics = disaster????
Right now, the Arduinos are being housed in cheap plastic soap-boxes I purchased at the dollar store and cut the appropriate holes in for electronics.
My questions are:
Am I in serious danger of frying all the Arduinos/ electronics just by keeping them inside of sculptures made of various insulating materials (mostly wool, bamboo-rayon, and polyester)?
if so, how can I best protect the electronic components? Is there any value in trying to build faraday cages for each of them? Should I run the ground pin to something metal to discharge potential buildup? (For casing, I had originally looked at pre-fab plastic Arduino cases, but they are slightly too big to fit with the mp3 shields on them). Do I need a conductive cases? If this would be useful, is anyone aware of any slightly-oversized (bigger than an Arduino Uno) conductive boxes that can be used or modified to protect in-use Arduinos from ESD in high-charge environments?)
Are the necessary holes in the Arduino casing (to run power and signal from) a potential entry point for ESD?
Can ESD make its way through a speaker, up speaker wire, and fry to board that way?
Any ideas why the speaker might be responding to the presence of wool?
Lastly, I have also been running the power cord out with the sensor cables and speaker cables. Is this a problem? Do I need to run them perpendicular or separate (will running them alongside each other cause interference in this context)?
Any advice is greatly appreciated. Thanks in advance!
ESD is created when two different types of materials are rubbed together. One material will collect electrons from the other resulting in a voltage charge. Having low humidity helps make this collection create higher voltages.
For this to happen things have to be moving (not air moves) and can collect or proved electrons to another material. Look here for a list of materials and their propensity to create ESD.
ESD will go right through a speaker, unless the frame is grounded, then it will likely to right to ground.
Typically to protect from ESD one would physically place all wires going to a board in one location (i.e. bundle them). Then put a 0.1µF capacitor from each wire to the power supply common.
Are you SURE it is wool? Wool comes from sheep and is organic and very unlikely to be involved with static electricity. Besides static electricity takes TWO electrodes and energy from movement to remove or add electrons.
BET what you are calling "wool" is actually all or part synthetic fiber which will CERTAINLY be involved with static electricity generation.
Paul
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Ok, The the next thing is the be sure every piece of metal in your device is connected to a common ground and that is connected to the AC power ground. That includes any speaker metal frames.
Thanks John. So this means that the wires from the sensor, the speaker wire, and the power cord can all be bundled? Does this mean wrapping them in something, or just tying them together?
There is only 1 power cable, does that change anything?
How are you powering the Arduinos? Through the 5V pin is the preferred way, if it is through the power jack you problem might just be overheating instead of static.
I think we need to power this way because there are no computers or breadboards involved in this design and we need them to be able to turn on and off with a light switch (they will plug into adaptors on track-lighting sockets)
Forgive the noobie question, but do you mean a wall-adaptor 5v supply? I am having a hard time envisioning a 5v power supply that is not just an adaptor
9 Volt adapter ---> Arduino uno power jack ----> through the UNO ---- > 5V to sensors
If so the Arduino is not designed to generate enough 5V power for many sensors and if your audio is also from the Arduino you are really in much worse shape.
