Wrist strap and ESD
shawnpwilson
Posts: 10
The only place I can play with a basic stamp and electronics is in a room with wall-to-wall carpeting.
If I strap an ESD strap to my wrist and clip the other end to the chasis of a computer ( turned on or off), will that provide the necessary grounding of ESD so I don't damage my basic stamp, its programming board, and various other circuits?
Thanks to all for their input.
Shawn
If I strap an ESD strap to my wrist and clip the other end to the chasis of a computer ( turned on or off), will that provide the necessary grounding of ESD so I don't damage my basic stamp, its programming board, and various other circuits?
Thanks to all for their input.
Shawn
Comments
I think much of the paranoia about ESD is just that. But the idea is keep you and the objects your working on at the same potential. So connecting to the computer chassis will keep YOU at ground potential, but the circuits may not be at ground potential.
I would connect the wrist strap to the GND of the breadboard that you are working on, and maybe connect that to the chassis ground (through a 1Meg resistor, ALWAYS use a 1MEG resistor, NEVER CONNECT A WRIST STRAP DIRECTLY TO ANYTHING WITHOUT GOING THROUGH A 1 MEG RESISTOR if the object your connected to should ever short to the AC mains your toast).
Most wrist straps have a resistor built-in, but I never trust that...
Bean.
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Those that would give up freedom for security will have neither.
·
Put on a kettle of tea while you work.
Happily I live in the sub-tropics and much of the year is is 90% humidity.
No rugs and no static. I guess that is why Taiwan is an electronic fabrication mecca.
Many office supply houses have large plastic rug covers [noparse][[/noparse]somewhat T shaped] for placing a chair behind an office desk in a carpeted office.
You can buy one and put it at your work station, under your chair.
Not only will it lessen the static build-up, small parts will not be lost in the carpet, AND your chair will roll quick easily.
Finally, If you put a 'touch plate' [noparse][[/noparse]which is connected to ground] on the front edge of your work bench. You can quickly 'discharge yourself' whenever you sit down. It is a lot less cumbersome than putting on and taking off a wrist strap. [noparse][[/noparse]And far less likely to kill you.]
Try using a grounded metal yardstick attached to the desktop with double adhesive tape as it is a lot cheaper than the high tech solutions.
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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
It’s not necessarily the voltage levels that do component damage, rather it is the sudden discharge of voltage that zaps the delicate components which is why a 1meg resistor is used. The resistors allows for a slow safe discharge when you touch a grounded object.·
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Mike
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I live in the Netherlands, Europe. So we run things on 230 AC voltage. If you connect your PC to a non-earthed wall socket then the chassis of the PC will carry a voltage as high as half the supply voltage! So in my case it will be 115 volts. This is caused by the filter capacitors in the switching power supply. They NEED proper earthing. I noticed this when i had to reach for something in my server rack. My ear lobe was touching the metal of the computer case and i appearantly touched something else that had earth potential. Ofcourse i received a nasty jolt.
So, back to the discussion... If you connect an ESD cord to your PC when the PC is not earthed properly, i would guess that, when touching your project, an AC voltage will pass through your body into your project, if the project has some means of ground or earth.
Correct me if i am wrong on this, but this was something i experienced first hand...
Ed.
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A horse is a horse, of course of course...
Post Edited (Mr.Ed) : 12/11/2005 10:26:48 PM GMT
A correct ground should be direct [noparse][[/noparse]as Mr. Ed] points out. Anything less may be altered or fail when most needed.
Regarding shocks, I suppose we all get them from time to time and we all know they are dangerous. Generally I avoid anything live above 120VAC if I can possibly do so.
One tip is to keep one hand in your pocket when working on live circuits. This way a shock will not go through one hand and out the other. Apparently that path is right across your heart and liable to send you to your local morgue.
An never remove insulation with your bare teeth. I acquired that habit in my teens and stopped just short of putting a hot lead into my mouth. I think I was about 14 at the time and standing on a wooden ladder. Nothing may have happened but who would ever want to find out?
The one meg resistor is quite a good idea.
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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
The air inside your house/office/facility is basically a chunk of the same air that is outdoors.· Humidity is basically a vapor pressure of the water, and there is enough leakage so that the "absolute" humidity will tend to equalize (sans a humidifier).
This means that the air inside and outside will try and approach the same volume of water vaper per cubic foot(meter) of air.· Because there is a bigger (near infinite for this discussion) volume of air outside, this will tend to the level things balance out at.
When the air outside is cold, it carries less moisture/water vapor per cubic foot.· This same amount (per cubic foot) is in the air inside.· Because the air inside is warmer, it's "relative" humidity is lower.· In winter in Wisconsin and other areas, much lower.· Hence it seems "dryer", and in terms of effect on static discharge, is dryer, and we see more "shocks" and ESD problems in winter.
Humidifiers help by replacing water in the air faster than it can "leaK" outside, and raise the relative humidity indoors.· This helps disapate the static electricity as it builds up.
Static electricity still builds up when it is humid, it just disipates faster, and is less of a problem.
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John R.
8 + 8 = 10
How about wearing rubber gloves; like the ones doctors use when they do checkups ...?