E-textiles EMC/FCC and durability issues

  • Thread starter Thread starter kb_designer
  • Start date Start date
  • Tags Tags
    Issues
AI Thread Summary
Building a keyboard sewn into a shirt raises concerns about EMC/FCC compliance, particularly with conductive thread and potential interference with other devices. The risk of affecting other devices is uncertain, but shielding is recommended to mitigate issues, especially if there are gaps in the shielding. A 1-2mm hole in the shielding could allow RF signals to penetrate, particularly for frequencies above 1 GHz. Durability of the conductive thread is crucial, with stainless steel fibers being a common choice, but alternatives may exist that better withstand flexing and stretching. Overall, careful design and shielding strategies are essential to minimize EMC/FCC risks.
kb_designer
Messages
2
Reaction score
0
I am trying to build a keyboard sewn into a shirt and I wonder if I need to worry about EMC/FCC issues with the conductive thread to the keys? For each key I use a normal (but very thin) pushbutton, the wire length to the arduino controller will be no more than 150 mm and I will use DC 3-5v. Because I debounce the signals from the buttons I assume that EMC won't be an issue for my stuff, but what about other devices?

It will most likely be a low volume product (no more than 100 units) and I don't think I can afford to do proper EMC/FCC certification so my plan is to shield everything that needs shielding and then keep my fingers crossed that the FCC won't show up at my door.

If shielding is needed then I think I can do it by adding conductive fabric or paint over and under the conductive wires.

1. How big is the risk that my device will effect other devices and thus potentially anger the FCC?
2. How big is the risk that my device will be effected despite debouncing?
3. If I have a "hole" in my shielding that is 1-2mm wide and 150mm long will that allow RF signals do go through and cause EMC/FCC issues?
4. What is the most durable choice of material for the conductive thread? From what I've read it is supposed to be stainless steel fibers but perhaps there is a better choice? Clothing means it will go through lots and lots of flexing and stretching.
 
Engineering news on Phys.org
kb_designer said:
3. If I have a "hole" in my shielding that is 1-2mm wide and 150mm long will that allow RF signals do go through and cause EMC/FCC issues?
A slot with longest linear dimension, L = 150mm, in a shield is a perfect slot antenna for EM waves with wavelength λ = 2L = 300mm, or 1 GHz. In other words, the slot will pass anything above 1 GHz without attenuation. Below 1 GHz, the Shield Effectiveness (SE) increases with 20dB per decade according to SE = 20 log (λ/2L).

qp2Qt9Z.png


Source: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CCwQFjAA&url=http%3A%2F%2Fwww.lairdtech.com%2FWorkArea%2Flinkit.aspx%3FLinkIdentifier%3Did%26ItemID%3D3400&ei=Bt7VUbrkLaGn4gSdmYCQCA&usg=AFQjCNGcU7gzJdO6s7PK9BOV51BBuJVLYA&sig2=ZrtyPU28KJ3hLtPV2Yk1lQ&bvm=bv.48705608,d.bGE [pdf]
 
Last edited:
Thread 'Weird near-field phenomenon I get in my EM simulation'
I recently made a basic simulation of wire antennas and I am not sure if the near field in my simulation is modeled correctly. One of the things that worry me is the fact that sometimes I see in my simulation "movements" in the near field that seems to be faster than the speed of wave propagation I defined (the speed of light in the simulation). Specifically I see "nodes" of low amplitude in the E field that are quickly "emitted" from the antenna and then slow down as they approach the far...
Hello dear reader, a brief introduction: Some 4 years ago someone started developing health related issues, apparently due to exposure to RF & ELF related frequencies and/or fields (Magnetic). This is currently becoming known as EHS. (Electromagnetic hypersensitivity is a claimed sensitivity to electromagnetic fields, to which adverse symptoms are attributed.) She experiences a deep burning sensation throughout her entire body, leaving her in pain and exhausted after a pulse has occurred...
Back
Top