[Discussion] question about fans

[Robert Carter]

I have another question about the tachometer signal from the fan. From  
what I have read the way to make use of this signal is to measure it  
with respect to ground - producing a square wave between ground and  
the supply voltage?  With a scope, would it be enough to connect the  
probe to the tach. line and the earth of that probe to the ground, to  
take a measurement?

Rob

On 3/12/2010, at 2:28 PM, Robert Carter wrote:

> Thanks guys thats useful to know.
>
> Rob
>
> On 3/12/2010, at 11:35 AM, Richard wrote:
>
>> Measure the speed of it.
>>
>> If there is a 4th wire like most new fans have that is to control  
>> the speed
>> of it rather than just doing PWM on the power which can result in  
>> lousy
>> spinup and speed fluctuations on the fan.
>>
>>> -----Original Message-----
>>> From: discussion-bounces at creativespace.org.nz [mailto:discussion-
>>> bounces at creativespace.org.nz] On Behalf Of Robert Carter
>>> Sent: Friday, 3 December 2010 8:00 a.m.
>>> To: discussion at creativespace.org.nz
>>> Subject: [Discussion] question about fans
>>>
>>> A 12V DC fan sometimes has three wires. A 9V battery on the red and
>>> black makes it go. What would the other wire be for?
>>>
>>> Rob
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> work blog:
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> rob at mintmedia.co.nz
> @vdu23
>
>
>
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