If this thing is (and it appears to be) a 'current transformer' then you 
have to be careful!

The 50 ohm resistor is referred to as a 'burden' resistor and is absolutely 
required (unless built into the device). Without it the voltage can jump to 
surprising values.

Bob Ammerman
RAm Systems




----- Original Message ----- 
From: "Tim ODriscoll" <tim@stokepogesway.net>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Thursday, December 15, 2005 5:57 PM
Subject: Re: [EE:] Detecting a blown lamp


> Thanks for all the ideas..
>
> I'd like to use the torroidal current sensor, I think.. No huge reason
> except that I've not tried any a/d before and I quite like the idea of
> being able to detect what kind of bulb is in the lamp. Although if I
> can't get it to work, the bridge-rectifier/opto idea would be next.
>
> I think I may have interpreted the data sheet wrong for the torroid I
> intend to use, so I've drawn a copy for others' opinions who have
> hopefully used something similar. I had inferred from the attached
> diagram that there was a resistance of 50 ohms through the actual
> device, but in retrospect, I think it may mean I have to supply one
> externally.
>
> I'm still not having any luck with Google in finding out how to hook up
> one of these things either.. I used to like those 'example circuits' and
> 'typical applications' at the end of data sheets.. It's probably one of
> those things that's so simple everyone already knows so no-one thinks of
> writing it down.. Now I know how my Mum feels when she tries something I
> find simple like setting the clock on the microwave..
>
> Cheers,
>
> Tim.
>


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