Machsupport Forum

Mach Discussion => Mach4 General Discussion => Topic started by: dunnitagain on September 06, 2017, 07:56:53 AM

Title: Hall Effect for Spindle Speed Feedback
Post by: dunnitagain on September 06, 2017, 07:56:53 AM

 


    Can a Hall Effect be used as Spindle Speed Feedback ? I have a LARGE ! VMC that has high and low range speed through belts, but had a Hall sensor from the OEM .
For Spindle speed feed back. I have Mach4 , everthing works, but spindle has no reference to Mach4 for accurate RPM. I have dspmc from Vital Sytems

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: joeaverage on September 06, 2017, 02:45:33 PM

Hi,
Hall effect sensor should be perfect for the job. Are you electronically inclined? Do you have a circuit idea in mind?

Craig

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: dunnitagain on September 06, 2017, 03:09:23 PM

  I wasn't sure if it was a simple hook up to my dspMC break out board or not . I'm functional at electronics  ;D but no expert by any means .
I can build circuits with direction and do some repair. Do I have to make an interface circuit ?

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: joeaverage on September 06, 2017, 06:05:53 PM

Hi,
depending on the Hall sensor you may need something like a schmitt trigger or comparator.
Other sensors have logic level outputs, all that's required is a supply.

Carig

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: joeaverage on September 08, 2017, 05:35:21 PM

Hi,
trolling around the Element14 website:

http://nz.element14.com/allegro-microsystems/a1301eua-t/hall-effect-sensor-sip-3-1301/dp/1198085 (http://nz.element14.com/allegro-microsystems/a1301eua-t/hall-effect-sensor-sip-3-1301/dp/1198085)
is an example of a linear hall sensor, this device would require a schmitt trigger or comapartor in addition
to the sensor IC.

http://nz.element14.com/allegro-microsystems/a1301eua-t/hall-effect-sensor-sip-3-1301/dp/1198085 (http://nz.element14.com/allegro-microsystems/a1301eua-t/hall-effect-sensor-sip-3-1301/dp/1198085)
is an example of a switching type, note that it even has a built in pull-up resistor. If you have a 5V supply you're golden.
There are examples without the pull-up and they have much wider power supply limits and might be worthwhile
if you only have a 24V supply.

Craig

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: joeaverage on September 08, 2017, 06:01:43 PM

Hi,
my apologies, the second link is a duplicate...it should've been:
http://nz.element14.com/honeywell/ss411p/sensor-hall-effect-bipolar-to/dp/1784734 (http://nz.element14.com/honeywell/ss411p/sensor-hall-effect-bipolar-to/dp/1784734)

Craig

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: RICH on September 09, 2017, 05:24:42 AM

FWIW,
Radio Shack did sell a small 1/8" diameter  x 1/16" high rare earth  magnet. Very easy to just crazy glue to about anywhere
making sensor installation very easy.

RICH

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: dunnitagain on September 09, 2017, 08:01:58 AM

 Thanks for the help joeaverage, It may be just easier to put a prox in the halls place and move on. I was hoping naively that it was plug and play!

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: joeaverage on September 09, 2017, 09:19:28 AM

Hi,
does a proximity have the bandwidth for an rpm sensor?

The last link I posted requires three wires, 0V,5V and signal.

Craig

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: joeaverage on September 09, 2017, 08:02:08 PM

Hi dunnitagain,
do you have the 7535 IO termination board fitted? If not then the digital IOs of the DSPMC J4,J5,J11 and J12 are 3.3V capable and non isolated
per page 13 of the manual. The warning makes it pretty plain if you put 24V onto one of the inputs you'll blow it, in fact I would under no circumstances
put 5V on them either. 3.3V TTL is great stuff, fast as hell and really low power but don't do anything silly with it, its just not fault tolerant. Ask me how
I know and I will post you some ICs that I have VERY CUNNINGLY let the smoke out of!

No matter whether you use a proximity sensor or a hall sensor in absence of the 7535 board you must signal the input pin with 3.3V. I had a quick look
at the specs for an Omron prox sensor and it had a bandwidth of 500Hz, should be good for anything but a highspeed (>20,000rpm) spindle. However
the proximity sensor signalled full supply voltage, 10V min. So you would need some sort if interface which would include a 3.3V zener to prevent the
sensor from blowing the input pin.

The Honeywell hall sensor I linked has a power supply range of 2.7V to 7V, ie if you had a 3.3V supply or could derive one from a 5V output on the DSPMC
with a low dropout linear regulator then no interface is required, the signal from the hall sensor can be hooked directly to the input pin of the DSPMC.

If you do have the 7535 board then the prox sensor is pretty much plug and play.

Craig

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: dunnitagain on September 09, 2017, 09:43:13 PM

Thanks Joeaverage! I wasnt looking that in depth , I think I can Piggyback off of the Spindle VFD encoder to a 7711 board an dhave my spindle feedback.

Title: Re: Hall Effect for Spindle Speed Feedback
Post by: dunnitagain on September 10, 2017, 10:08:13 PM

 Success ! I found a differential encoder feed from the VFD , interfaced with my 7711 board , through the dsPMC and presto! I have spindle speed.
Thanks for the Help!