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10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz
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Dave D
electronics forum Guru


Joined: 08 Sep 2005
Posts: 486

PostPosted: Wed Apr 05, 2006 12:32 am    Post subject: Re: Any value in cleaning inside old monitor? Reply with quote

"Sam Goldwasser" <sam@saul.cis.upenn.edu> wrote in message
news:6wvetqf90g.fsf@saul.cis.upenn.edu...
Quote:
David Peters <no-email@mail.com> writes:


<snip>

Quote:

Let the flame wars begin... NOW! ;-)


No war from me, I agree totally!

Dave
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tjs
electronics forum beginner


Joined: 15 Sep 2005
Posts: 2

PostPosted: Wed Apr 05, 2006 12:59 pm    Post subject: Re: Computer room static blowing server power supplies Reply with quote

An update; We are investigating "zinc whiskers" phenomina as a possible
cause. The zinc filaments are produced from the plywood core floor panels
supported by the zinc electrocoted support structure. When floor panels are
lifted or disturbed the conductive dust can get into the power supply and
lead to shorts between the modern closely spaced SMT devices.
See here for a white paper http://www.dataclean.com/pdf/zincwhiskers3.pdf

The failures/arcs in our supplies have all arced from the 120vac chopper
regulator collector to the PS case. If the zinc whisker problem is our case
then the blue flash is just a 120/170p-p vac arc to ground, and not a static
discharge.

We are looking at replacing our floor tiles with the modern ultra low static
floor tiles.

I'm a little skeptical that this is the problem, but it is true that 2
months ago we pulled floor tiles to look for fiber conduits and that about
the time the problems began

TJS


"T" <anon@anon.org> wrote in message
news:Y-2dnR409fOTR6_ZnZ2dnUVZ_tmdnZ2d@adelphia.com...
Quote:
A raised floor server room with 6 servers, fiber optic patch panels, large
control system cabinets and large UPS system, has been recently been
plagued
by computer power supply failures. The supplies fail when apparently many
tens of thousands of volts jump from inside the PS around the switching
regulators to the chassis of the supply taking out all the components.
This
has happened to 8 supplies so far. A visible blue flash has been witnessed
several times by pewrsons in the room.

The servers so far affected are all sitting on the raised computer center
floor. What ususally happens seems to be when a person enters the 12x20ft
room or gets near a server a large snap is heard and the server is on the
backup redundant PS, if it has not already failed.

We have been adding grounding bonding from all computer case to the bldg
steel, raised floor structure, etc to try to stop this. Its still
happening.
The computers are various brands and varoious ages, from 1 week old to 5
years old. The probelm began occuring 2 months ago. The data center was
built 12 years ago.

We are at a loss to figure out how the charge is building up on the inside
of the power supplies. I am thinking about the common power source, via
the
power cords Hot, Neutral and Ground conductor.

The green wire should be bonded to the PC case. Apparently the PS
regulator
board floats above chassis potential. Apparently a large potential
differnce
is building. It jumps a 1 inch gap to the chassis. Burn marks from
repeated
arc overs are evindent (the arc that makes it fail is not the 1st time it
occurs!)

The Hot and Nuetral..how could a charge be coming in on these conductors
and
getting past the MOVs to build a potential on the boards.


Any ideas would be appreciated.
TJS




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Franc Zabkar
electronics forum Guru


Joined: 01 May 2005
Posts: 616

PostPosted: Wed Apr 05, 2006 10:05 pm    Post subject: Re: Computer room static blowing server power supplies Reply with quote

On Wed, 05 Apr 2006 12:59:59 GMT, "TJS" <anon@anon.net> put finger to
keyboard and composed:

Quote:
An update; We are investigating "zinc whiskers" phenomina as a possible
cause. The zinc filaments are produced from the plywood core floor panels
supported by the zinc electrocoted support structure. When floor panels are
lifted or disturbed the conductive dust can get into the power supply and
lead to shorts between the modern closely spaced SMT devices.
See here for a white paper http://www.dataclean.com/pdf/zincwhiskers3.pdf

The failures/arcs in our supplies have all arced from the 120vac chopper
regulator collector to the PS case. If the zinc whisker problem is our case
then the blue flash is just a 120/170p-p vac arc to ground, and not a static
discharge.

We are looking at replacing our floor tiles with the modern ultra low static
floor tiles.

I'm a little skeptical that this is the problem, but it is true that 2
months ago we pulled floor tiles to look for fiber conduits and that about
the time the problems began

TJS

What are the chances of zinc whiskers causing *exactly* the same fault
in *8* PSUs?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
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Palindr☻me
electronics forum addict


Joined: 10 May 2005
Posts: 76

PostPosted: Fri Apr 14, 2006 7:29 pm    Post subject: Re: Adding extra device to all-in-one PIR lantern Reply with quote

Graham W wrote:
Quote:

Jamie wrote:

Zak wrote:


I have a PIR-actived outdoor courtesy light. The PIR and the
lantern's lamp bulb are both inside the same single housing. This
runs off the mains (UK 240 volts). This is it:
http://www.focusdiy.co.uk/content/ebiz/focus/invt/23489/23489.jpg

I would like to modify this so that when the PIR detects something
then I get a notification inside the house. Perhaps from a beeper
or another lamp bulb.

-----

However I can only work with the mains supply because the PIR and
the lamp bulb are effectively one inseperable unit and also are
not easy to access.

Can I interrupt the 3 core mains supply to the lantern as a whole
and insert a device in SERIES (either in the neutral or in the
live lead)such that when the PIR fires and circuit is closed then
this device would actuate?

The impedance of the device woul dhave to be modest or it would
draw power from the PIR circuit and from the bulb circuit causing
both to potentially work wrongly.

Are there any device which would work in this setup? In the old
days maybe a relay would have been inserted in-line with one of
the mains supply wires and the relay's contact would actuate a
device. Mayeb there is there *simple* modern equivalent of the
realy which can be used if I can't wire a sounder or a bulb
stright in?


yes, a CT, (current transformer) then a comparator circuit to
trip on a current set point.


Complicated!

What I did was to find an octal plugin relay whose coil current was
close to the demand of the PIR unit when the lamp was lit. This will
be a low voltage AC coil type or use a bridge rectifier for a DC coil.

The screw terminal plug-in base is easy to mount. Does the job
wonderfully!

Break the AC feed and measure the current then insert the coil
of a suitable relay in series with two ends. The AC feed can be used
directly through the relay contacts to activate a lamp or mains
buzzer etc.


Unfortunately, if the lamp or lamp fitting is changed to one with a high

efficiency, low wattage lamp, the relay will no longer operate. Worse,
if a higher wattage lamp is used, the relay coil will be absorb excess
power, with the possibility of fire. A zener diode of adequate wattage,
across the coil would be an improvement, as would fitting a capacitor to
reduce relay chatter (assuming the bridge rectifier is used, in both
cases). At the very least the protection (eg fusing) for this circuit
would need to be calculated and downrated. It is always possible that
the person implementing this alarm could be run over by a bus and the
new owner assume that the circuit is safe and standard.

The low voltage relay (say a 3v relay) coil insulation may not be rated
for peak 240 volt mains ac. Thus risking the possibility of insulation
breakdown, fire, electric shock, etc.

If wired into the live conductor, the whole circuit will be live. If
wired into the neutral, the remainder of the lamp circuit will become
live if the relay is unplugged or failed.

There are much better ways of implementing this safely.

--
Sue
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techie_alison
electronics forum addict


Joined: 27 Sep 2005
Posts: 89

PostPosted: Fri Apr 14, 2006 7:36 pm    Post subject: Re: PCB Prototype Supply!!! Reply with quote

<njsldz@163.com> wrote in message
news:1144998216.307429.4530@i39g2000cwa.googlegroups.com...
Quote:
if any question, please send mail us!!!!!!

Sell high quality HDI PCB (CHINA)

we send pcb by DHL or UPS ( Send to USA About 1 days from china)

Has anyone tried out these guys?

I've used the Hong Kong suppliers (reluctantly at first) for a few things
and found them excellent value for money as well as reliable. Sometimes you
wouldn't believe they're 5000 miles away when a local company 500 yards away
could make such a hash up of things.
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Mike Meakin
electronics forum beginner


Joined: 26 May 2005
Posts: 11

PostPosted: Fri Apr 14, 2006 7:41 pm    Post subject: Re: PCB Prototype Supply!!! Reply with quote

Are there any Hong Kong suppliers you would particularly recommend ?



"techie_alison" <retro@dial.pipex.com> wrote in message
news:46KdnXkK-MG1ZaLZRVny1w@bt.com...
Quote:
njsldz@163.com> wrote in message
news:1144998216.307429.4530@i39g2000cwa.googlegroups.com...
if any question, please send mail us!!!!!!

Sell high quality HDI PCB (CHINA)

we send pcb by DHL or UPS ( Send to USA About 1 days from china)

Has anyone tried out these guys?

I've used the Hong Kong suppliers (reluctantly at first) for a few things
and found them excellent value for money as well as reliable. Sometimes
you
wouldn't believe they're 5000 miles away when a local company 500 yards
away
could make such a hash up of things.

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Walter Harley
electronics forum Guru


Joined: 25 Mar 2005
Posts: 367

PostPosted: Sat Apr 15, 2006 6:16 am    Post subject: Re: PCB Prototype Supply!!! Reply with quote

"techie_alison" <retro@dial.pipex.com> wrote in message
news:46KdnXkK-MG1ZaLZRVny1w@bt.com...
Quote:
njsldz@163.com> wrote in message
news:1144998216.307429.4530@i39g2000cwa.googlegroups.com...
if any question, please send mail us!!!!!!

Sell high quality HDI PCB (CHINA)

we send pcb by DHL or UPS ( Send to USA About 1 days from china)

Has anyone tried out these guys?


I thought about it, but I'm reluctant to do business with someone who abuses
the newsgroups so incessantly.
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Robert Baer
electronics forum Guru


Joined: 25 Mar 2005
Posts: 1159

PostPosted: Sat Apr 15, 2006 9:27 am    Post subject: Re: Spring Sale Reply with quote

DAMN!
I was really hoping that you had springs on sale.
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Alan Holmes
electronics forum beginner


Joined: 19 Dec 2005
Posts: 13

PostPosted: Sat Apr 15, 2006 4:20 pm    Post subject: Re: Spring Sale Reply with quote

"Denise" <kdsprod@comcast.net> wrote in message
news:1145047042_8719@sp6iad.superfeed.net...
Quote:
Get up to 50% Off our Ultimate Protein Plus Weight Loss Program now
through the end of April.

And what price are the springs?

Alan
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Christian HOSTELET
electronics forum beginner


Joined: 16 Jan 2006
Posts: 8

PostPosted: Sun Apr 16, 2006 8:40 am    Post subject: Re: PCB Prototype Supply!!! Reply with quote

"Walter Harley" <walterh@cafewalterNOSPAM.com> a crit dans le message de
news: 94qdnVlPeZopEt3ZnZ2dnUVZ_uidnZ2d@speakeasy.net...
Quote:
"techie_alison" <retro@dial.pipex.com> wrote in message
njsldz@163.com> wrote in message
if any question, please send mail us!!!!!!

Sell high quality HDI PCB (CHINA)

we send pcb by DHL or UPS ( Send to USA About 1 days from china)

Has anyone tried out these guys?


I thought about it, but I'm reluctant to do business with someone who
abuses the newsgroups so incessantly.


I just tried PCBCart (China) and was very satisfied with them (price,
leadtime, quality).
Was also reluctant to use a "so-remote" supplier but all went well. Good
support.

---
Christian - Grenoble
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techie_alison
electronics forum addict


Joined: 27 Sep 2005
Posts: 89

PostPosted: Sun Apr 16, 2006 10:34 am    Post subject: Re: PCB Prototype Supply!!! Reply with quote

"Mike Meakin" <mike@nikam.freeserve.co.uk> wrote in message
news:e1ottn$or5$1@newsg2.svr.pol.co.uk...
Quote:
Are there any Hong Kong suppliers you would particularly recommend ?




Just the odd eBay ones really. I think they're quite keen to make a mark
for themselves over here. And I'm one of the most cynical people going when
it comes to things going wrong, pleasantly reassured.

So naturally interested in the OP, I'd rather give them a chance than some
begrudged UK company with an angry secretary and oh-so-many orders that they
don't need customers. There's only one company in the UK I'm trialling at
the moment, seem pretty good so far if not their prices are different to
those published for standard jobs...
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Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Sun Apr 16, 2006 1:57 pm    Post subject: Re: Spring Sale Reply with quote

Robert Baer wrote:
Quote:

DAMN!
I was really hoping that you had springs on sale.


I can give you a great deal on trampoline springs, I've got hundreds
of the things hiding in my garage and shop. I already took several sets
of legs to the recycling center, but more springs just keep showing up,
week after week. :(

Anyone want to make it REALLY hard to push their gas pedal to the
floor? ;-)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
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Robert Baer
electronics forum Guru


Joined: 25 Mar 2005
Posts: 1159

PostPosted: Mon Apr 17, 2006 2:35 am    Post subject: Re: for sale: internetDotComs.com Reply with quote

I bid two cents.
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Sophie
electronics forum beginner


Joined: 28 Mar 2006
Posts: 15

PostPosted: Mon Apr 17, 2006 3:46 am    Post subject: Re: PCB Prototype Supply!!! Reply with quote

Dear Madam/Sir:

Glad to know you through the Internet!

Are you in need of LCD products?

SEAKO ELECTRONIC CO., LTD (HUAXIAN PHOTOELECTRIC CO., LTD Qingdao
Branch )is the professional supplier of LCDs from
China. We offer all kinds of LCD products including COB, COG, TAB type
LCD Module and TFT monitor/TV. Standard products or customer design
projects are both available here.

Considering the improvements it offers, we believe you will find our
HUAXIAN a very good product. Because we have always been faithful in
carrying out its contracts, reasonable in price, superior in quality,
timely in delivery, flexible in trade, the Corp. Serves clients
wholeheartedly. Foreign friends are warmly welcome to establish trade
ties.
It will be a great pleasure to receive your inquiries for any of the
items against which we will send you our lowest quotations.

Remember, we care about your business and our highly trained R&D team
will work closely with you to meet all your requirement.

Yours faithfully,
Sophie
Sales manager
Qingdao Seako Electronics Co., LTD
HUAXIAN PHOTOELECTRIC CO., LTD Qingdao Branch
402, No 1009 Dalao Road, Qingdao, China
Tel: +86-532-87061859
Fax: +86-532-87061859
MSN:sophie_seako@hotmail.com
Email:qd_seako@126.com

njsldz@163.com 写道:

Quote:
if any question, please send mail us!!!!!!

Sell high quality HDI PCB (CHINA)

we send pcb by DHL or UPS ( Send to USA About 1 days from china)


Product Name: Printed Circuit BoardPlace of Origin: ChinaFeatures:
1) Surface finish: hot air solder leveling, entice, immersion gold,
carbon ink, gold finger, peelable mask
2) PCB file format: protel,powerpcb,Gerber file,Engle....
3) Profile: routing, punching, V-Cut, chamfered
4) Number of layers for mass production: 2 - 12
5) Finished copper weight from .25 to 3oz
6) Minimum finished hole size .006"
7) Min. trace .004" - Min. space .004"
Cool Max. panel size: 18" x 24"
9) Printed circuit board final thickness from .016" to .125"
10)soldermask /Legend in a variety of colors
(Green,White,Black,Yellow,Red..)
11)operating costs (10 pieces ): 2 layers( about 0.048$/inch) 4
layers(about 0.096$/inch)

Lead times: 2 layers( 1 days, 3 days, 5 days) Ships next day.
4 layers( 2 days, 5 days, 7 days)
6 layers( 3 days, 5 days, 8 days)



we send pcb by DHL or UPS ( Send to USA About 1 days from china)

Min Qty 3pcs.

Company Name: Nanjing Xilun Printed Circuit Board Co., Ltd.
Contact Person: Mr. Ding JiaBao
Leave me a message
Address: 9 Changjiang Road, Nanjing City, JiangShu Province. China
Zip: 210016
Telephone: 86-025-8606 1148
Fax: 86-025-8695 7829
Website: http://www.njpcb.com
E-mail: sales@njpcb.com


if any question,Please send e-mail to us,we will reply as soon.
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techie_alison
electronics forum addict


Joined: 27 Sep 2005
Posts: 89

PostPosted: Mon Apr 17, 2006 9:24 am    Post subject: Re: PCB Prototype Supply!!! Reply with quote

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:94qdnVlPeZopEt3ZnZ2dnUVZ_uidnZ2d@speakeasy.net...
Quote:
Has anyone tried out these guys?


I thought about it, but I'm reluctant to do business with someone who
abuses
the newsgroups so incessantly.



Yes, slightly coming round to that way of thinking. Instead of responding
to their just wares, another pun advertisement is blindly dropped in, this
time for LCDs. Buyers are fickle. I'll stick with the angry secretary for
the time being.
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Google

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