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zeshan
Joined: 07 Nov 2009
Posts: 10
Location: pakistan
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 07 Nov 2009 17:09 Measurement of RPM's of Dc Motor |
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| how can i exactly measure the RPM's of a fast DC motor (15000 RPM)????????are such motors available in Markets?plz guide me
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hameeds01
Joined: 23 Aug 2005
Posts: 308
Helped: 15
Location: NUST Islamabad
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07 Nov 2009 17:15 Re: Measurement of RPM's of Dc Motor |
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via infrared sensor
http://www.edaboard.com/ftopic370126.html
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zeshan
Joined: 07 Nov 2009
Posts: 10
Location: pakistan
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07 Nov 2009 17:26 Re: Measurement of RPM's of Dc Motor |
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| thanx.but are not these Expensive????? I M A STUDENT and want toimplement for my project
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haker_fox
Joined: 24 Jun 2009
Posts: 51
Helped: 4
Location: Russia, Irkutsk
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08 Nov 2009 15:06 Re: Measurement of RPM's of Dc Motor |
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| zeshan wrote: |
| how can i exactly measure the RPM's of a fast DC motor (15000 RPM)????????are such motors available in Markets?plz guide me |
If only need to measure the RPM take any open optocoupler and slotted disk. So you wiil be able to do that! If you also want to measure angular position you should be ready to spent much of money. Encoders for high speed are very expensive.
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zeshan
Joined: 07 Nov 2009
Posts: 10
Location: pakistan
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08 Nov 2009 16:08 Re: Measurement of RPM's of Dc Motor |
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| how much money? what about the availablity of such motors?????? plz guide
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ark5230
Joined: 29 Jun 2009
Posts: 188
Helped: 15
Location: India
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haker_fox
Joined: 24 Jun 2009
Posts: 51
Helped: 4
Location: Russia, Irkutsk
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09 Nov 2009 1:20 Re: Measurement of RPM's of Dc Motor |
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| zeshan wrote: |
| how much money? what about the availablity of such motors?????? plz guide |
Quiet! As I told you if you only need to measure the angular velocity you shouldn't worry about the cost.
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Google
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09 Nov 2009 1:20 Ads |
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hameeds01
Joined: 23 Aug 2005
Posts: 308
Helped: 15
Location: NUST Islamabad
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09 Nov 2009 7:13 Re: Measurement of RPM's of Dc Motor |
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u can get these optical sensors free
just find an old Ball mouse thatz it
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pranam77
Joined: 22 Apr 2008
Posts: 1071
Helped: 94
Location: Mangalore(India)
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09 Nov 2009 8:31 Re: Measurement of RPM's of Dc Motor |
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| zeshan wrote: |
| thanx.but are not these Expensive????? I M A STUDENT and want toimplement for my project |
When you say you need to measure the speed up to 15000 RPM, the circuit or the sensor too shud be fast enough to process and display the same. Thus if you are calculative with the component cost, so will be the results. Cheers.
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zeshan
Joined: 07 Nov 2009
Posts: 10
Location: pakistan
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09 Nov 2009 10:29 Re: Measurement of RPM's of Dc Motor |
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| can optocoupler help us measuring upto 15000 RPM????????? Acurately
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betwixt
Joined: 04 Jul 2009
Posts: 388
Helped: 64
Location: Wales, UK
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09 Nov 2009 10:41 Re: Measurement of RPM's of Dc Motor |
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Yes, all you need is an opto-coupler, or more accurately an opto switch.
You need access to something rotating on the motor, it could just be a point on the motor shaft but it gets easier if you can use something with a larger diameter. All you have to do is use a reflective opto switch and place it close to the moving part. Make a section of the moving part reflective and part of it non-reflective. The light from the opto switch shines on the part and whether or not it sees a reflection depends on the rotational angle (reflective or non-reflective section is in front of the switch). all you have to do then is count the frequency of the reflections, you get one per revolution so it is easy to measure.
If you can access a disk rotating on the shaft you can do the same thing by passing or blocking light through it and using a slotted opto switch instead.
I would be cautious about using a ball mouse opto system, with typically 100 holes in the wheel and at 15,000 RPM the pulses would be very fast, possibly 25KHz or more so counting might be more difficult.
Brian.
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