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3-Feb-2010 16:25 Tim Harrison How do you detect an AC current, 4mA<I<3A, Pmax<3W ?
29-Jan-2010 06:09 admin Re: Forum
28-Jan-2010 15:50 Maurice Kemmann Forum
sticky admin Welcome, how to post.


13-Feb-2010 15:31 admin Re: How do you detect an AC current?

Hello Tim,

Indeed this is an idea, The problem with this idea is that, at low loads, the signal is very weak, requiring a lot of amplification. This makes it noise senstive. Besides that, the transformer would be rather bulky. I have a preliminary solution using two schottky diodes.

3-Feb-2010 16:25 Tim Harrison How do you detect an AC current, 4mA<I<3A, Pmax<3W ?

Hi Ruud

Was thinking about this one, and started along the lines of a mains clamp on ammeter. Then got to passing the mains load wire through a ferrite (torriod?) and having a sense wire as a second winding. Solves the power dissipation problem, and introduces mains isolation at the same time if it is needed. Not sure how big the torriod/transformer would have to be though.

Considering the range of currents you plan to measure, some non-linear transfer function in the sense circuit may be of use to bias low value currents to occupy a greater part of the scale. I'm not a lot of use regarding the detailed engineering I'm afraid. But the general idea may be of some use to the project.

Best Regards, Tim.

29-Jan-2010 06:09 admin Re: Forum

Hi Maurice,

Thanks for your support. Yes, there is still a lot to do. A this moment I am designing the AccessNode, and redesigning the current detection parts on the DimNode and SwitchNode. The latter is not so easy as it may seem. How do you detect an AC current in the mains, in the interval I>4mA & I<3A, while the generated power is below 1W? Further requirements: not to many (but obtainable!) components, small and cheap. The present solution produces to much heat above I>1A.


28-Jan-2010 15:50 Maurice Kemmann Forum

Hi Ruud,

your home automation project sounds really good. I am not very familliar with your FemtoOS by now but maybe this will change within the next weeks.

I am looking forward to follow the project and maybe to help, if i can. ;-)

Kind regards,
Maurice "Mucki" Kemmann

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