I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

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AnthonyL

On Friday, August 30, 2013 10:00:54 AM UTC+1, AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade

fan. Any easy ideas?



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AnthonyL

Have you got a multimeter that measures AC frequency ?
If so, you might be able to cobble together something with a battery, photocell and a light source.
Or you could rig it so it just clips a piece of card or something and compare by ear the pitch with comparison tones from the internet.
Simon.

AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

http://www.ebay.com.au/itm/Handheld-...item2a1dfef7ae

In article ,
AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

Is it mains or battery?

--
*Never slap a man who's chewing tobacco *

Dave Plowman London SW
To e-mail, change noise into sound.

On Fri, 30 Aug 2013 11:22:36 +0100, "Dave Plowman (News)"
wrote:

In article ,
AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

Is it mains or battery?

Sorry, should have said it was standard mains. Two speed.


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AnthonyL

AnthonyL wrote:
On Fri, 30 Aug 2013 11:22:36 +0100, "Dave Plowman (News)"
wrote:

In article ,
AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?
Is it mains or battery?

Sorry, should have said it was standard mains. Two speed.


If the motor doesn't have any brushes, and there's no gears it'll be
3000rpm or slightly below. Some of them are 1500rpm, and they have 4
pole motors.,

Otherwise, the model aircraft bods use non-contact tachometers, and for
a one-off measurement, you might be able to borrow one from a local
model shop.

--
Tciao for Now!

John.

Light beam interruption and divide by three?

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"AnthonyL" wrote in message
...
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

--
AnthonyL

AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

Put a thin white line on one blade. Photograph the fan whilst it rotates
at various shutter speeds. Calculate the RPM from the angular movement
of the line at each shutter speed. Average the result.

Bill

On Fri, 30 Aug 2013 13:49:35 +0100, Bill Wright wrote:

Put a thin white line on one blade. Photograph the fan whilst it rotates
at various shutter speeds. Calculate the RPM from the angular movement
of the line at each shutter speed. Average the result.

From the motion blur, I like that. Don't use flash though. B-)

--
Cheers
Dave.

On 30/08/2013 13:49, Bill Wright wrote:
AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

Put a thin white line on one blade. Photograph the fan whilst it rotates
at various shutter speeds. Calculate the RPM from the angular movement
of the line at each shutter speed. Average the result.

Bill

I had a similar thought and, convinced someone must have written an app
to do it, went looking in both the Android and iOS market. Was somewhat
surprised no one has written one yet. Unless the camera hardware isn't
up to it

My programming skills certainly aren't!

Lee

"AnthonyL" wrote in message
...
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

--
AnthonyL


What sort of motor is it?
Very small motors are difficult to measure as the measuring device can
disturb it.

Lee wrote:
On 30/08/2013 13:49, Bill Wright wrote:
AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?

Put a thin white line on one blade. Photograph the fan whilst it rotates
at various shutter speeds. Calculate the RPM from the angular movement
of the line at each shutter speed. Average the result.

Bill

I had a similar thought and, convinced someone must have written an app
to do it, went looking in both the Android and iOS market. Was somewhat
surprised no one has written one yet. Unless the camera hardware isn't
up to it

My programming skills certainly aren't!

Lee
On a related topic a guy I knew in the 60s who repaired cameras used to
adjust rollerblind shutters by photographing a TV screen and counting
the TV lines on the picture.

Who remembers the white square in the corner of the neg frame caused by
the Zenit mirror not returning quickly enough?

Bill

On Fri, 30 Aug 2013 16:57:21 +0100 (BST), "Dave Liquorice"
wrote:

On Fri, 30 Aug 2013 13:49:35 +0100, Bill Wright wrote:

Put a thin white line on one blade. Photograph the fan whilst it rotates
at various shutter speeds. Calculate the RPM from the angular movement
of the line at each shutter speed. Average the result.

From the motion blur, I like that. Don't use flash though. B-)


It works to a point but the beginning and the end of the blur are hard
to determine. I get around 3,400 rpm at low speed which could well be
3,000 rpm. I like the idea of having a laser tacho (not sure why, I
just like the idea) as suggested by F Murtz so I've ordered one from
amazon.uk at less than a tenner.



--
AnthonyL

In article ,
John Williamson writes:
AnthonyL wrote:
On Fri, 30 Aug 2013 11:22:36 +0100, "Dave Plowman (News)"
wrote:

In article ,
AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade
fan. Any easy ideas?
Is it mains or battery?

Sorry, should have said it was standard mains. Two speed.


If the motor doesn't have any brushes, and there's no gears it'll be
3000rpm or slightly below. Some of them are 1500rpm, and they have 4
pole motors.,

That's assuming it's synchronous or near synchronous.
Lots of induction motors aren't, e.g. the shaded pole motors
very often used for driving mains fans (they couldn't be speed
switchable if they were synchronous).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Sat, 31 Aug 2013 10:15:08 GMT, lid (AnthonyL)
wrote:


It works to a point but the beginning and the end of the blur are hard
to determine. I get around 3,400 rpm at low speed which could well be
3,000 rpm. I like the idea of having a laser tacho (not sure why, I
just like the idea) as suggested by F Murtz so I've ordered one from
amazon.uk at less than a tenner.


.... but not fully concentrating I've just realised it is coming from
China!

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AnthonyL