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I am building an enclosure for a Beaglebone and external circuit that I want to be able to wear, and therefore want to be lightweight and somewhat comfortable. I power the Beaglebone using a battery pack that's about 5 volts.

Right now, I enclosed the Beaglebone and the external circuit within an antistatic bag. This is the first layer of protection. I enclosed the antistatic bag with a jersey fabric material. The jersey fabric material has Velcro attached to it and is attached to a Velcro belt.

Is the powered Beaglebone circuit safe within the antistatic bag? Antistatic bags are slightly conductive according to the Wikipedia article, so I am unsure if this a safe solution. If not, what is a good insulating material? Rubber?

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Keep in mind that what is generally considered "anti-static" doesn't mean ESD safe. What is typically considered "anti-static" are those pink/lightly colored bags which prevent buildup of charge. These aren't really conductive at all, maybe the ever so slightest bit of conductivity and I doubt your board will run into any issues with shorts and such (keep in mind Joe's comments). However, these bags do not prevent an external ESD source (say, your charged finger tips) from zapping a chip on the board.

ESD bags or static-shielded bags (silvery colored) are designed to be fully ESD safe, though as you've noted they do have the caveat of being slightly conductive. I took my multimeter (datasheet claims max range of 40 Meg Ohms) and tried to measure the resistivity and couldn't get any readings on a spare ESD bag I had until the probes physically touched each other. Your mileage may vary, but it will most likely be ok from a conductivity/electrical point of view. Again, keep Joe's comments in mind about other factors which may matter.

As an aside, you might be able to get away without using ESD shielding bags/anti-static bags at all depending on what other packaging you have.

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    \$\begingroup\$ Why not use the anti-static bag as a first layer, and the ESD bag as a second layer. The first bag layer will protect the circuit from any issues which could arise from the conductance of the ESD bag, which will protect the whole thing from charged fingers. \$\endgroup\$ – Kurt E. Clothier Aug 28 '13 at 1:06
  • \$\begingroup\$ I suspect you'd struggle to measure an ESD bag with a normal DMM, you might need a megger-type insulation tester to put some proper volts across it - after all, static is in the thousands of volts range. \$\endgroup\$ – John U Aug 28 '13 at 7:46
  • \$\begingroup\$ @JohnU I think that's the point: regular electronics won't really be effectively shorted when in contact with the ESD bag, but static can't penetrate it. \$\endgroup\$ – helloworld922 Aug 28 '13 at 15:43
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    \$\begingroup\$ @KurtE.Clothier Interesting idea, though I would just use a small hard enclosure instead. This protects your board from ESD and some physical trauma (it's hard to bend or knock off components when they're inside a box). Don't know how much of a problem this is with the device at hand. \$\endgroup\$ – helloworld922 Aug 28 '13 at 15:45
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If the Beaglebone and other circuit are completely enclosed in a sealed antistatic bag, with no holes in the bag, no switches or LEDs poking out of the bag, no cables going through the bag, then the Beaglebone is safe from static. If that's not the case then you need to supply much more information about the electrical and physical arrangement of your circuits. Of course, any electronic device operated inside a sealed plastic bag will get hotter than if it had air convection to cool it, so the Beaglebone might not work very well.

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Remember that modern circuits all have discharge diodes that discharge pins to the supply lines. This makes all circuits static resistant to some extent as soon as they are connected to the supply lines.

Manufacturers also use conformal coating to prevent damp corrosion and other problems. Epoxy coating the completed board will make it very safe to wear but difficult to repair or test.

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  • \$\begingroup\$ That chip level protection is enough to save the chip from most of the stress during handling and soldering. However board level ESD protecion does need at least TVS diodes. Also consider system level ESD protection, which may introduce further challenges (e.g. metal chassis or not, protective earth connection or not). There is a lot of information on the web on chip level, board level and system level esd. \$\endgroup\$ – Gee Bee Jun 19 '17 at 14:14
  • \$\begingroup\$ Note that is in fact the protection diodes discharging to the power supply that mitigates high voltages on the chip itself. If no power supply is connected the chip capacitance is very low and the chance of destruction much higher. \$\endgroup\$ – skvery Jun 20 '17 at 6:12

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