Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 11-11-2009, 09:41 AM   #16
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Share |
Default

Getting small shock from household electronics cases (in Asia). Why?


>>see below
Quote:
Originally Posted by scootley View Post
I connected one end of a wire to a water supply pipe. I connected the other end to one terminal of a small light bulb rated that said "12V 5W" on it.
>>So the hot resistance of this lamp is (12^2)/5 = 29 ohms, and the cold resistance is 10x or 15x lower.
It takes 400 mA to light.

The light does not illuminate.

>>So the current is less than 400 mA.

With the light connected, I measured the AC voltage between the 2 terminals of the light, which reads 0V.
>>see below
Is this the measurement you were talking about?
>>Yes
With a cold resistance of 3 ohms or less, and a shock current of ~1 mA you'd see 3 mV across this 12v bulb.

I would try a 120v incand.lamp of low wattage. The filament has a higher resistance.

Better yet, substitute a 1k, 1/4w or larger resistor for your body. If you read 1vac you've got your 1 mA shock current. If you read 10vac you've got 10 mA through this low value resistor.
Most people with a large contact area and dry skin will have a resistance of 1k to 6k.
http://bme.ccny.cuny.edu/faculty/mbi...tageReview.pdf

Yoyizit is offline   Reply With Quote
Old 11-11-2009, 10:09 PM   #17
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,838
Default

Getting small shock from household electronics cases (in Asia). Why?


Quote:
Originally Posted by scootley View Post
I With the light connected, I measured the AC voltage between the 2 terminals of the light, which reads 0V.

Is this the measurement you were talking about?
Yes. As you observed, connecting the light "drained" to ground the current that was giving shocks, and that current was very small given that the light did not come on. I would consider it safe to ground the equipment to a known ground (attach the wire directly, no light connected in between) and not worry about it any more.

__________________
Stop wasting time re-adjusting the pattern. Have several lawn sprinklers, one for each pattern.

Last edited by AllanJ; 11-11-2009 at 10:12 PM.
AllanJ is offline   Reply With Quote
Reply

Tags
enclosure, ground, polarized, shock


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.