Thanks, yes, I understand.
So does that mean that the ground is definitley connected to the case, and therefore, when my hands are on the case, I am grounded?
If so, those looking to be grounded (earthing) while using a Macbook have that benefit, due to the alluminum case vs some other computer with a plastic case.
Now for the next idea. I understand that EMFs are much less when unplugged and running on battery. So now I'm wondering, is it better for the body to be unplugged and running on battery or plugged into the ground and having the body grounded, even though there are higher EMFs?
This question is really not for standard computer nerds or electricians, but rather for those who find this thread and have a good knowledge of earthing, EMFs and their affect on the human body.
Currently Being ModeratedFeb 5, 2013 9:55 AM (in response to medicinemanKE)
The DC side of the MagSafe power adapter cable has only two wires in it. One is wrapped around the other as a braid. There is no independent Earth/Ground connection all the way through to the chassis.Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers
Currently Being ModeratedFeb 5, 2013 10:20 AM (in response to Grant Bennet-Alder)
OK, thanks. So help me understand this. In google searches I read about people feeling electricity from their macbook through their hands and that plugging in with the grounded cable solved it.
Also, I don't understand how the "appliance" could be safe if it's not grounded to the chassis. If there is a short, it goes into the user right? Doesn't make sense to me why it would not be grounded to the chassis.
Another question: Could I open it up and easily find a way to ground it to the chassis? It might be hard to tell where the ground is in there I guess.
Currently Being ModeratedFeb 5, 2013 10:31 AM (in response to medicinemanKE)
The DC side of the power adapter produces about 16.5 Volts DC.
Underwriters Labs (UL) requires that you not be able to access anything over 35 Volts AC or DC with your bare fingers.
The talk about "grounding the chassis of Appliances" comes from Appliances that are using 110 Volts tot 220 Volts internally.Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers
Currently Being ModeratedFeb 5, 2013 10:32 AM (in response to Grant Bennet-Alder)
Oh, yea, only 16.5 Volts DC is coming down that line from the white box forward right? Got it.
I would still love to be able to find the ground in the computer and connect it to the case.
Currently Being ModeratedFeb 5, 2013 10:45 AM (in response to Grant Bennet-Alder)
Grant Bennet-Alder wrote:
The DC side of the MagSafe power adapter cable has only two wires in it. One is wrapped around the other as a braid. There is no independent Earth/Ground connection all the way through to the chassis.
That is incorrect, if you are using an Apple 3 pin connector on the magsafe the ground is connected via the metal mushroomy looking thing at the connection to the Magsafe. Search back, I posted photographs of the connection a few months ago.
You can also connect one side of a voltmeter to ground and the other to the mushroomy looking thing (or the MBP casing) and check that way. It is grounded if using a 3 pin AC connector (an Apple one)
Thanks for chiming in.
It is entirely possible that one of the two DC wires to the computer IS Earth Gound, and the other provides about +16.5 Volts or -16.5 Volts relative to earth ground.
That is the "Classic" way we teach Electrical Engineering Circuit Design in the US, and it would be a sensible and economical way to design it.Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers
Currently Being ModeratedFeb 5, 2013 10:56 AM (in response to Grant Bennet-Alder)
Yes, that is what I think is happening on the DC side, as far as I could test the chassis is at earth (ground) potential (simple to test) with the 3 pin connection to the mains supply, and it floats without. Safe either way but the 3 pin connectors will occasionally trigger a ground loop state, easy to tell when your hear the buzz on the audio.
I connected a volt meter set to check continuity to the ground of a three prong outlet. I could not get the volt meter to register short by touching the other lead to the case of the Macbook pro. It just registered "OPEN". Then I changed the setting to the continuity setting used to check diodes and I did get it to register some numbers that way by touching the case. A ground tester is included with the earthing kit (http://www.earthingsolutions.ca/help_answer.asp?ID=15) and so I tried that next. The green light comes on when I touch the end of the power cord that goes into the side of the Macbook. The green light comes on when I touch the areas over the speakers, but anywhere else on the case does not turn the green light on. I guess I have to conclude that there is not a very effective ground at the point where the hands rest on the case.
Yea, green at the headphone jack on the 2010 Macbook pro but not on the 2012 Retina. However, I accidentally discovered something. If I put my hand on the area where the wrists rest and then put the earthing tester on my hand I get a green light. So I figured it was like you said with humidity. So then I licked the earthing tester and put it on the case where the wrists rest...green light.
So my conclusion now is that I am grounded sufficiently while plugged in.
Thanks for all of the help!!!