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Hall Effect rpm sensor

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Mike Welch

Joined: 13 Feb 2011
Posts: 272

Posted: Mon Jun 18, 2012 2:23 pm Post subject: Hall Effect rpm sensor

List guys,



  Can someone direct me to "complete rpm sensor circuit", including either a digital or analog gauge

that would go along with it?

  I have need of something that will display visually a rotating motor's shaft.  A Hall Effect circuit

would be fine, but I'm open to anyone's suggestion if they have a better idea how to monitor rpms

of a motor.  FYI, the motors will turn at a relatively slow 200-250 rpm (if that matters).

  If you know of a specific gauge, or LCD display, that could read these rpms, I'd appreciate that, too.

Thanks in advance,

Mike Welch



 [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jun 19, 2012 6:55 am Post subject: Hall Effect rpm sensor

At 05:21 PM 6/18/2012, you wrote:

  	  Quote: 	
		  List guys,



   Can someone direct me to "complete rpm sensor circuit", including either a digital or analog gauge

 that would go along with it?



   I have need of something that will display visually a rotating motor's shaft.  A Hall Effect circuit

 would be fine, but I'm open to anyone's suggestion if they have a better idea how to monitor rpms

 of a motor.  FYI, the motors will turn at a relatively slow 200-250 rpm (if that matters).



   If you know of a specific gauge, or LCD display, that could read these rpms, I'd appreciate that, too.



 Thanks in advance,

 Mike Welch 	


   What is the rpm range of interest? Is the

   instrument to be permanently mounted or is

   it a 'test' or 'setup' environment that could

   use a hand-held? See:



  http://tinyurl.com/77ulekb



  http://tinyurl.com/77lw4bs



   If you need a permanent, panel mounted

   instrument, you could use something like

   this



  http://tinyurl.com/7nxrh4w



   but you'd need to build a sensor and

   some interface electronics. As long as

   you're building stuff, the data can be

   displayed on a small, analog instrument

   where a customized scale sized to your

   task is pretty easy.



   



  



 



 

   Bob . . .    [quote][b]

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Mike Welch

Joined: 13 Feb 2011
Posts: 272

Posted: Tue Jun 19, 2012 7:33 am Post subject: Hall Effect rpm sensor

Bob,



  Thank you for replying!  

Here are some of the parameters:

1)  motor shafts are anticipated to rotate between 0-300 rpm

2)  the tach-displays need to be remotely, and permanently mounted (in a console)

(I really like that digital tach you suggested!!)

3)  the 'precise' motor rpms do not have to be "highly accurate", but they do need to be consistant.

(in other words, if the shaft is actually spinning at 307 rpms, and the gauge says "320", that's fine, as long as 

each time it is consistantly off the same amount!)

  I did find a very nice electronics package that was close to what I'm looking for, but it had a couple of 

glitches.  First glitch was the rpm range it measured, which was way too high, and the second glitch was the 

two 7 segment displays, when I would prefer an actual tachometer like the one you suggested.

  See:

http://www.eio.com/p-23310-velleman-k2625-digital-tachometer.aspx

  Thanks for your help, Bob,

Mike





 		 	   		  

  [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jun 20, 2012 5:38 am Post subject: Hall Effect rpm sensor

At 10:32 AM 6/19/2012, you wrote:



  	  Quote: 	
		  Bob,



   Thank you for replying!  



 Here are some of the parameters:



 1)  motor shafts are anticipated to rotate between 0-300 rpm 	


   Okay, if you were going to display on an analog instrument,

   you'd want a sensor that was watching say, 10 events per

   revolution so that you were measuring 3000 evenst/min or

   50 events/second. It's hard to get a fast responding display

   that is also free of 'wiggles' when the measured frequency

   is below 20 Hz or so.



   With a digital instrument, one can measure the period of time

   between pulses and then calculate rpm . . . this technique

   will get you a good rpm measurement for every counted event.



  	  Quote: 	
		  2)  the tach-displays need to be remotely, and permanently mounted (in a console)

 (I really like that digital tach you suggested!!) 	


   This is an automotive device that probably expects to

   get a signal from the ignition system. It's scaled internally

   to present shaft rpm when the engine produces 3 or 4

   ignition events per revolution. The specs on this instrument

   are suspect when they said, "A tach adapter may be required if

   you have a multiple coil ignition system to ensure a proper signal."



   It didn't mention whether the instrument had a jumper setting

   to allow tailoring the installation to cars of different

   engine sizes. I've built tach adapters that would convert

   observed shaft RPM into a signal that would emulate an

   engine . . . but that's a bit of added fuss that you

   probably want to avoid if practical.

  



  	  Quote: 	
		  3)  the 'precise' motor rpms do not have to be "highly accurate", but they do need to be consistant.

 (in other words, if the shaft is actually spinning at 307 rpms, and the gauge says "320", that's fine, as long as 

 each time it is consistantly off the same amount!) 	


   Digital can and should be quite accurate and very

   repeatable to +/- one least significant digit.

   But how sensitive is your process to RPM variations

   in the 1 LSD range? 320 real RPM on some tachs might

   produce a 319-320-321 "wobble" in readings. In other

   words, just how accurate dose the displayed speed

   reading need to be. Again, having lots of events per

   revolution (10-20 toothed gear to stroke your sensor).



 

  	  Quote: 	
		    I did find a very nice electronics package that was close to what I'm looking for, but it had a couple of 

 glitches.  First glitch was the rpm range it measured, which was way too high, and the second glitch was the 

 two 7 segment displays, when I would prefer an actual tachometer like the one you suggested.

   See:

  http://www.eio.com/p-23310-velleman-k2625-digital-tachometer.aspx

 

   Thanks for your help, Bob, 	


   You've probably seen the response from Jim Hausch.

   He's no doubt slain this dragon many times. Why

   don't you guys strike up a battle plan on the List?

   I'll join in if I think I've got something extra to

   contribute but I'll bet Jim can handle it.



   If it turns out that you do need some kind of data

   conversion device, We might be able to accommodate

   the requirement with custom software in the open

   source, digital wig-wag project board. Our byte

   herding friends here on the List could probably

   get the board to sing, dance and do dishes for your

   application.



 

   Bob . . .    [quote][b]

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jhausch

Joined: 14 Jan 2008
Posts: 35

Posted: Thu Jun 21, 2012 3:59 am Post subject: Re: Hall Effect rpm sensor

Bob,



I have been receiving Mike's responses to my email.  I only receive a daily digest from the list.  I will leave it up to him to post the collection/recap of our conversation on the web.   



I was a bit surprised to see my work email signature pop up on the list, but I guess that's the nature of the internet.



I've contacted encoder and prox vendors looking for 100' submersible solutions.  I think that is the most challenging part of this application as viewed from my world.  We have items rated for high pressure washdown, but 3 atm of constant pressure is likely another story....  You'd think a fully potted solid state solution would be fine, but my gut tells me the saltwater will creep in at the cable entry point and perhaps along the mating surfaces between the housing and potting material - searching for any void it can find to get at the electronics....



I agree with you that multiple PPR (pulses per rev) are needed to provide some accuracy/display stability.  



We'll see where this goes... certainly an interesting application.

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 21, 2012 3:00 pm Post subject: Hall Effect rpm sensor

At 06:59 AM 6/21/2012, you wrote:




Bob,



I have been receiving Mike's responses to my email.  I only receive a 

daily digest from the list.  I will leave it up to him to post the 

collection/recap of our conversation on the web.



I was a bit surprised to see my work email signature pop up on the 

list, but I guess that's the nature of the internet.



   You were in a cc list and the reply-all response got you

   dumped into the List data flow but not in the bucket of List

   subscribed addresses.



I've contacted encoder and prox vendors looking for 100' submersible 

solutions.  I think that is the most challenging part of this 

application as viewed from my world.  We have items rated for high 

pressure washdown, but 3 atm of constant pressure is likely another 

story....  You'd think a fully potted solid state solution would be 

fine, but my gut tells me the saltwater will creep in at the cable 

entry point and perhaps along the mating surfaces between the housing 

and potting material - searching for any void it can find to get at 

the electronics....



   If you can find a square-wave (hall effect) driven instrument

   with the approrpiate features for scaling say 3000 ppm to a 300

   rpm display, we can hammer a high pressure sensor together.



I agree with you that multiple PPR (pulses per rev) are needed to 

provide some accuracy/display stability.

We'll see where this goes... certainly an interesting application.



   Agreed. Let's see what kind of shaft is exposed

   to the inquisitive world of instrumentation.



   Bob . . .

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