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Getting data from low voltage apparatus fed by a mains unit

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Getting data from low voltage apparatus fed by a mains unit

Postby inschris » Sun Oct 16, 2005 8:50 pm

Greetings all! I contemplate
using ADC-11 to supervise voltages and temperatures in a charging
apparatus for up to 4 cells. The currents may be up to 2A per cell
and I contemplate getting this DC current, at low voltage (maybe only
5V DC) from a 250V 50Hz mains unit (?maybe from the desktop computer's power supply?).
i) Am I right in understanding that all signals
connected to the ADC- 11 must be grounded to the ground of the
computer's motherboard? Ie, the charging circuit(s) would have to be
grounded to the ground of the computer's motherboard?
ii) How can I
get an overview of the options/ techniques for ensuring that the
charging apparatus, and the ADC-11, do not become connected to any
mains-side conductor? Eg, how is the mains in a printer, or in an
external mains power supply for a laptop, isolated from the low-
voltage circuits which are connected to the computer? Is it normal
for the mains earth to be connected to the computer casing and/or
motherboard earth? Can anyone refer me to document(s) on this matter?

Thanks in anticipation.
inschris
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Postby Sarah » Tue Oct 18, 2005 9:06 am

Hi

Thank you for your post.

The ADC-11 takes it's ground through the power supply of the computer, therefore all signals connected to the ADC-11 will have the same ground as this.

As for interference from other mains sources, I do not know of any literature on this, and cannot guarantee that it will not occur. I have not however had any problems with this myself, however I have not tried an application such as yours.

Best Regards
Sarah
 

Getting data from low voltage apparatus fed by a mains unit

Postby inschris » Tue Oct 18, 2005 9:14 pm

Thanks, Sarah, for the reply. In my questions, especially ii), I wasn't thinking so much of some kind of distortion of the data obtained. Rather my concern was, what is common rationale / technique in order to ensure that the ADC-11, and even the motherboard and/or parallel port, do not get damaged by high voltages in the same apparatus, as eg the voltage in the mains-side parts of a printer? Does one simply rely on the isolation between the primary (mains-side) and secondary (low voltage) windings of the transformer? What about the case of a desktop computer's power supply, which likewise has components connected to mains?

I will be grateful if anyone can refer me to a treatment(s) of this topic.
inschris
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