larry@kitty.UUCP (Larry Lippman) (11/23/87)
Since this article deals with construction of an effective, but low cost surge protector, I have cross-posted to some other newsgroups. I have always felt that surge protectors are sold at an artificially high price and represent a consumer ripoff; here is a way to fight back... In article <1805@ukecc.engr.uky.edu>, edward@engr.uky.edu (Edward C. Bennett) writes: > >Does anybody know of any *cheap* power conditioning which might > >significantly improve my 3B1's chances of survival? Thanks. > > Now that I've got a 3B1, I've been concerned about power problems also. > What are the important things to look for? Spike/surge/transient protection? > For a start, I pulled out the ol' Radio Shack catalog. They've got two > units that seem reasonable. > > Under "AC Outlet Voltage Spike Protectors" there's a 6-outlet > power strip with noise filter and circuit breaker for $29.95. > > Over in computer accessories there's a 2-outlet power protector > with "full common and differential mode transient protection" > (What is that? A fancy way of saying voltage spikes?), noise > filtration and a MOV status lamp for $18.95. > > Comments? Horror stories? The idea of paying $70 for one of these things > at a "computer emporium" seems outrageous! Your're right; the prices of surge protectors are outrageous - especially when you find out how much the actual surge protector components really cost! Don't get ripped of - build your own surge protector. It's really simple, and the cost savings will astound you. The following is a description of how to build a surge protector which offers dual protection: (1) using MOV's (metal oxide varistor) and (2) using a gas discharge tube. You will need the following components, all manufactured by Siemens: 1 ea 3-electrode gas discharge surge protector, P/N T61-C350 $ 3.30 3 ea Metal oxide varistor, P/N S20K130 @ $ 0.82 $ 2.46 As you can see, your total cost for the protector elements is $ 5.76. Many major electronic distributors carry Siemens. Two examples are Hamilton-Avnet and Allied Electronics. Allied Electronics will sell the above mail order; they do have a minimum order of $ 25.00, but will fill an order less than $ 25.00 for a $ 5.00 handling charge - still not a bad deal if you can't figure out anything else to order. Allied has a national toll-free number of 800/433-5700. _______________ AC LINE HOT_______| 15 AMP FUSE |_____________________________OUTLETS HOT (black) |_____________| | | | (black) | | | MOV ___|___ | | | GAS | | EARTH GROUND_______________________|_________|PROT.| MOV (green) | | |_____| | |__OUTLETS GROUND | | | (green) MOV | | | | | AC LINE NEUTRAL____________________|____________|__________|__OUTLETS NEUTRAL (white) (white) The following design and construction notes apply: 1. "AC line hot" = black wire = duplex outlet narrow slot "AC line neutral" = white wire = duplex outlet wide slot "AC line ground" = green wire = duplex outlet round opening 2. Build the protector circuitry in a 2x4 electrical "handy box". Mount a fuseholder in the box for a 3AG 15 amp fuse, along with a terminal strip to facilitate mounting the circuit elements and making necessary connections. Cover the box with a blank cover plate. 3. Feed the box with a three-wire AC line cord of at least 16 AWG; use of 14 AWG is preferred. Connect a second cord to the box; this cord (which should be kept reasonably short) can feed a multiple-outlet plug strip. 4. As an alternative to a second cord, use one or more electrical pipe nipples and feed additional electrical boxes which contain duplex outlets (much less money than a plug strip, but not as "pretty" in appearance). If you use this method, run a wire to each outlet ground terminal instead of relying upon the the metal electrical box for the ground connection. 5. Use a common point attached to the first electrical box to connect all ground wires; a 10-32 machine screw through the box is good. This common point should terminate: the power cord ground (green), one end of two MOV's, the center electrode of the gas tube, and the outlet ground (green). 6. Insulate all leads of the MOV's and gas protector tube using plastic insulating sleeving. Use 14 AWG wire for any internal connections. If possible, use insulated crimp terminals for connections. Make certain that the MOV's and gas protector tube do not touch the metal box. 7. To assure maximim effectiveness of the protector circuitry, run a wire from a cold water pipe or ground rod and connect it to the case of the electrical box containing the MOV's and gas protector tube. Use at least 12 AWG for this wire; a smaller gauge wire will defeat the purpose. While running a separate ground is not essential, surge protector ciruitry is more effective with a lower impedance to earth ground. An auxiliary ground wire assures such a low ground impedance. 8. This box contains no "idiot lights", which are really unnecessary and are just a sales gimmick anyhow. Can you really imagine SEEING a < 10 ms energy pulse on a so-called "surge indicator" lamp? :-) I make no guarantee that the above circuit will protect your computer or other electronic equipment from anything. However, I can assure you that the above design (if properly constructed) represents a surge protector which is equal or superior to anything sold by Radio Shack or any other retail store. And the do-it-yourself price is MUCH LESS than any alternative. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|utzoo|uunet}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
ralph@ncrcae.UUCP (11/25/87)
I am in the process of collecting material and references for my previous
request of Lightning Protection (lacking some ANSI/IEEE and NFPA standards).
But . . .
One of my reference materials, the Amateur Radio Relay League 1988 Handbook
suggests installing the General Electric "Home Lightning Protector" (Part
number 9L15BC002) at the power service entrance.
Before I got the ARRL Handbook, I had asked the electric utility supplying
me what was available. They said that they could install an optional
device at the meter that would suppress any surges that got past their
equipment (but not a direct strike; nothing can protect anything from a
direct strike). The utility installed a Secondary Surge Arrestor (Catalog
number J9200-10) from Joslyn Mfg. & Supply Co., Electrical Apparatus Div.
Installation was $30.00.
Check with your local electric utility company to see if they can install
one for you. Installation at the service entrance needs to be done by a
qualified installer with the main power cut.
The ARRL also recommends installing MOV's (Metal Oxide Varistors) at the
breaker box. (This, I have not done yet, but plan to.) Besides that, use
the surge protector outlet strips.
Secondary Surge Arrestors:
General Electric Co. General Semiconductor Industries
Semiconductor Div. PO Box 3078
W. Genesee St. Tempe, AZ 85281
Auburn, NY 13021 (TransZorbs)
(Home Lightning Protector,
and MOV's)
Joslyn Mfg. & Supply Co.
Electrical Apparatus Div.
(Address Unknown-Electric Utility provided).
Book references:
ARRL 1988 Handbook ($21.00 USA)
ARRL
225 Main St.
Newington, CT 06111
NFPA (National Fire Protection Association) Publications:
National Electrical Code 1987 (DJ-70-87HB $39.50)
Lightning Protection Code (NFPA-78 $12.00)
Protection Of Electronic Computer/Data Processing Equipment (NFPA-75 $10.50) *
Static Electricity (NFPA-77 $12.00) *
National Fire Protection Association
Batterymarch Park
Quincy, MA 02269
1-800-344-3555
* I have not ordered these but plan to. The Institute Of Electrical And
Electronics Engineers, Inc (IEEE) have some ANSI/IEEE standards that are
applicable to surge protection that I plan to order.
In a recent BYTE magazine, Steve Ciarcia (BYTE's construction editor),
mentioned that he had some equipment fried by lightning and is going to
write a future article on protective steps. The December 1981 issue (I
think) has a do-it-yourself article on surge protectors.
unix-pc.general was editied out of newsgroups since we don't get this group
and rn choked on it.
--
ralph@ncrcae.Columbia.NCR.COM <Ralph M. Hightower>
NCR Corp., Engineering & Manufacturing - Columbia, SC
Home of THE USC! (Oldest Public Funded University in USA)
South Carolina had a University 49 years before California was a state.doug@catuc.UUCP (doug) (11/26/87)
In article <2803@ncrcae.Columbia.NCR.COM>, ralph@ncrcae.Columbia.NCR.COM (Ralph Hightower) writes: > I am in the process of collecting material and references for my previous > request of Lightning Protection (lacking some ANSI/IEEE and NFPA standards). > I did some research into this area and was told that MOV's have a prpblem in that they degrade each time they absorb a surge and that the amount of energy they can absorb each time becomes less and less. Eventually they become ineffective. The bad part is that one cannot often tell if the part has absorbed any surges and how much useful life it has left. This means they they should be replaced periodically but that no one can tell you when. The gas discharge tubes can work repeatedly but are not very fast hence the reason they are often employed alongside the faster MOV's. One solution I'm told is to use a device called a transorb (Panasonic/Digikey sells them.) These are beefed up back-to-back zener diodes that can work repeatedly if not stressed beyond their maximum energy rating.
cgs@umd5.umd.edu (Chris Sylvain) (12/03/87)
In article <2626@catuc.UUCP> doug@catuc.UUCP (doug) writes: >I did some research into this area and was told that MOV's have a prpblem >in that they degrade each time they absorb a surge and that the amount of >energy they can absorb each time becomes less and less. Eventually they >become ineffective. If you have a GE data book handy, and look up the GE-MOV's, then you'll find a graph that indicates the amount of energy the device can dissipate (as heat) decreases with the number of pulses (surges) the device has already dissipated. Why is that? MOV's are constructed of particles of zinc oxide, the metal in Metal-Oxide Varistors. The particles of zinc oxide fuse together when they are heated. So, in time, yes the MOV becomes ineffective as a surge dissipater, as the zinc oxide finally conducts all the time, which dissipates a GREAT DEAL of heat. My experience with them is when they were used in cable TV satellite receivers I repaired. The MOV's are installed AFTER the power line fuse so that when they do fail, they open the fuse. They do fail spectacularly, too.. Zinc splattered (really no worse than a two "blob" solder-splash) over the personnel shield (a piece of plastic to keep fingers from 120VAC), the PC board charred under the MOV, and a blackened hole in the MOV. Replace the MOVs (three used), and the fuse -- the receiver functions literally like new. The power supply board isn't as pretty as when it was new, but with a little epoxy and a few pieces of buss wire, it's as good as it needed to be. -- --==---==---==-- .. and the mome raths outgrabe. .. ARPA: cgs@umd5.UMD.EDU BITNET: cgs%umd5@umd2 UUCP: ..!uunet!umd5.umd.edu!cgs