Feed polarity from alternator windings

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kingrat
Posts: 4
Joined: Tue Dec 11, 2007 5:55 pm
Location: Sheffield
Full Name: Paul Drabble

Feed polarity from alternator windings

Postby kingrat » Wed Feb 04, 2009 11:08 pm

Hi,
Can anyone tell me the polarity from the windings of the alternator to drive a rev counter. I would expect it to be negative, but just need confirmation if anyone can help.

Cheers

Paul

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davew
Chairman
Posts: 1949
Joined: Fri Jan 05, 2007 8:54 pm
Location: Knaresborough
Full Name: Dave White

Postby davew » Wed Feb 04, 2009 11:33 pm

Not sure what you mean by polarity, alternator RPM signals are normally taken off the rectifier (diode pack) and are half the unrectified signal. You just get the positive going half of the full sine wave.

In short, you get a positive pulse that appears at around 9v (depends on the alternator) from half the windings of the alternator.

Hope that makes sense !

cheers

Dave

kingrat
Posts: 4
Joined: Tue Dec 11, 2007 5:55 pm
Location: Sheffield
Full Name: Paul Drabble

Postby kingrat » Thu Feb 05, 2009 12:13 am

dave,
cheers for that, yes it does make sense, helps me out cos I was about to take a feed from the windings, as has been suggested else where. reason for asking is I bought a tacho which stated it took a feed from the W terminal and my alt has no such terminal, reading around suggested from the Windings as that is where the W phase is derived from.

Cheers

Paul


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