ant cosier wrote:
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hi guys thanks for your replies but i have couple of questions
1. if you use a hall sensor how would the micro read it


You need somekind of A/D process. Depending on the precision you are after you can do that with a couple of external bits and a comparator, or a dedicated AD.

2. can the micro(89c51rd2hba) measure voltage or current

See above.

Steve