I figure I'm going to get a lot of discussion here, so let me set out why I felt moved to start this thread. There are a lot of guys here who do computer work who have a less than optimal working environment (e.g., their kitchen table). I wanted to talk about work safety practices for the benefit of the community so that no one we know and love gets hurt or killed working with electrical equipment.
It's worth noting that 110vac single-phase "house current" has killed more people than any other form of electrical power.Let's make some BASIC ASSUMPTIONS:
BASIC WORK AREA PREPARATIONS:
- 1.) We are not working in an electronics shop environment with a fully equipped workbench, static mat, and a large array of test equipment. (We'll presume most folks are working on the nearest convenient sturdy table.)
- 2.) Nothing more sophisticated than basic hand tools, and maybe a soldering iron and multimeter and various "shop aids" as described are used during the work.
- 3.) The work in question can be anything from a full-blown build to repair, upgrade, or routine cleaning and maintenance.
With these assumptions, let's proceed with getting ready to work. The first steps are to set up the work area and plan your work. There are a few things which can be done to enhance the work area's effectiveness and safety:
1.) Clear off the work area. Get rid of anything not directly related to the work at hand
. Especially remove any loose objects, foods, or liquids which might get in the way of the work. If you smoke while you work, have a heavy ash tray or butt can (a coffee can with some sand in it) near the table to control any cigarettes, cigars, etc. when not in use, and use it. (A cigarette end can reach temperatures approaching 1600 deg F.)
2.) Clear enough workspace to be able to approach your work from as many angles as possible.
3.) The table or surface you are using should be stable and sturdy enough to support the weight of all the components you will be working on.
4.) Check to be certain that receptacles for power are close enough at hand to be useful. If this is not the case, move the table closer to them, or run an extension cord (being careful to route it to minimize tripping hazards). The last thing you want is power cords festooned all over the place.
5.) Consider having at least one power strip available with a "master off" switch. This gives you a safety "kill switch" that is close at hand if things go wrong. (Work on the gear long enough, and it will happen...)
6.) Once the work area is clear, put down a clean, dry cloth or vinyl table covering. (I use an old white sheet from a twin bed set we no longer use - makes a bright, clean work surface that helps keep screws and other fasteners from bouncing or skittering across the table, and makes them easier to find when dropped. It also help when laying out cables, fasteners, and other components prior to a build.)
7.) Stop for a moment if you have not already planned out your work and do it now. A work plan doesn't have to be a big deal, just a clear idea of what you're setting out to accomplish, how you intend to go about it, and what you will need to get the job done.
8.) Gather your tools, materials and components, and arrange them in a logical manner that facilitates your work plan.
9.) Provide yourself with a means of grounding any systems on which work is to be performed. This is very important, and should be done carefully. I'll cover some ways to do this effectively and safely without breaking the bank further on.
10.) Consider obtaining and using a pair of safety glasses whenever testing or operating a computer on the work table with the case open. (A cheap pair of clear, non-tinted safety glasses can be had for under $6.00 US. Small investment when you consider what could be at stake.)ELECTRICAL SAFETY:
There are some basic considerations for electrical safety when doing computer work. Electrical energies found in 110 vac current have sufficient force to be deadly to the human body, and to cause personal injury or equipment damage if improperly used. The first rule of Electrical Safety is:
1.) Always work with the power OFF whenever possible, especially when doing cold-pluggable component replacement/removal, or routine cleaning, repairs, or maintenance.
If you cannot work with the power OFF, remember:
2.) Before starting any work,
move pets and small children away from the work area for their protection and yours.
3.) If working in LIVE EQUIPMENT for testing or troubleshooting, wear eye protection, and remove all jewelry, watches, and other metallic objects from your person before starting work. That means out of your pockets, off your fingers, no wristwatches, necklaces, etc. Wear shoes with solid soles, preferably good rubber soles that will insulate you from ground.
4.) If working in LIVE EQUIPMENT, make sure you are NOT ALONE. Whoever is there with you needs to know how to kill power to your worktable if the need arises, and be able to get past you to safely pull the plug. PLEASE brief your "safety buddy" before starting work so they know you are working and need them there.STATIC ELECTRICITY & GROUNDING:
Most folks who do computer work to any degree have heard the warnings about static electricity being potentially damaging to delicate electronic components in a computer or other device. Most also know that grounding oneself helps get rid of static electricity.
Static electricity is not the primary reason systems are provided with a ground wire, though. Grounding a piece of equipment provides an "emergency path" for current to flow in the event of a short circuit. To use a technical term, it places the equipment at "ground potential" so that if a short occurs, the equipment's case and ground lead provide the quickest path to ground for the misplaced energy. This keeps YOU from becoming that path to ground. It's for your safety, and the safety of the electrical system providing the power.
I've heard it said on more than one occasion that leaving a computer plugged in but "OFF" while the case is open protects it from static discharges. While that is true, it does not totally de-energize the equipment. It also lays open the possibility of inadvertently powering up the equipment.
Some motherboards and power supply components need to be discharged before doing any removal of parts or connectors, and this cannot be done with the power cord plugged in. To this end, we will talk about proper grounding methods that make the computer truly safe to work on.GROUND LEAD:WARNING: a basic understanding of electricity and receptacle wiring is needed to build this and the Grounding Cord which follows. If you do not possess these skills, enlist the help of a competent, qualified person to do it for you. Mistakes in making up grounding connections can be fatal.
A ground lead is simply a length of stranded, insulated wire with a ring lug on one end for attachment to a grounding point, and an alligator clip for connecting to the case of a computer or other piece of equipment. It's easy to make one using a crimp-on lug and an alligator clip that either screws or solders on to the opposite end. About eight feet of wire is usually more than enough to reach. To make this ground lead really mobile, bolt the ring lug to the ground tab on a 2-wire to 3-wire AC adapter and plug it in to a regular receptacle. This will provide you with a ground lead which can be moved or carried in a toolbox for "house calls".EDIT: Whoops! When using a ground lead with a 2/3-wire adapter, DON'T forget to also leave a small lead to lug off the ground terminal to the receptacle ground. The adapter will only have two prongs (I had this backward in my head for some reason while writing... sorry!) A better way might be to make the lead up to a conventional 3-wire plug's grounding screw.GROUNDING CORD:
A grounding cord is made from a regular IEC-style PC Power cord, and a three-pronged male "valise" plug (available at a local hardware store or electrical supply house for a few dollars). Cut the molded on male end from the power cord, then dress the outer jacket back about two inches. Inside are three wires, in the colors white, black ,and green. Cut off the black and white wires close to the end of the jacket, and strip about 1/4" to 3/8" of the insulation from the end of the green wire. Slip the rear shell of the plug over the cord and far enough back to clear the working end, then connect the green wire's stripped end to the grounding screw on the male plug body and assemble the rear shell and strain relief over it.
What you will wind up with is something that looks like a power cord, but does not provide power, only a ground lead. This can be plugged into a computer on your work table and then to a receptacle to provide it with a safe path to ground without providing it power. (This is handy for those computers which require the technician to press the power button to discharge stored energy to kill a "Standby LED" on the board before doing any work...)
This post is getting rather long, so I'll stop here, and let the discussion commence. I invite all who read to participate, and to point out any flaws in the methods and procedures I mention thus far.
Thanks for reading. Let's work together safely.