Wiring Hall effect sensor

[louthedog]

I have been enjoying the TouchDro I installed a few months back. Works great! Always wanting to take it up a notch I have been working on installing the hardware for the Tach feature. I have the board with the MicroB connectors and plan on using a Sainsmart Hall effect sensor module. I have machined and installed a ring with 8 magnets on the lathe.  My electrical skills favor wiring a house and not so much micro circuitry so I need help on making the connections from the Sainsmart to the MicroB board. The Sainsmart module has solder terminals for a plus, negative, AO and DO. The Touchdro board has Tach labeled next to four unlabeled solder terminals. Which terminals do I use and which connection goes to what?

[louthedog]

Update: I was able to identify the connections to the Touchdro board and have the Sainsmart Hall Effect board hooked up and working...kinda. Sainsmart specs their board to operate down to 3.3 volts. I get a 3.25 volt reading with the voltage going low to 0.15 volts when a magnet is present. RPM readings seem to be pretty close below 400 rpm but higher rpm readings are quite low. For example when the machine is set to it's dial setting of 2800rpm the reading on the tablet is showing about half that. I started with 8 magnets and decided to pull magnets from my ring, reset the Touchdro accordingly and re-test to see if it made a difference. I'm now down to 1 magnet and readings are still similiar. I'm wondering if the rail voltage is just too low for proper operation. Also have read where a 10K pull down resistor needs to be installed for proper operation in some sensor set ups. Not sure if that applies here though. Wish I knew more about electronics. Any ideas?

[Ralphxyz]

I had similar results with my hall effect sensor running at 5 volts. Let us know if you find a solution.

Ralph

[Briney Eye]

I had good success with an infrared "obstacle avoidance sensor" and six small pieces of reflective tape stuck to the tail end of my spindle. Mounted the sensor 1/2" from the spindle and played with the angle until I got solid readings. I figured it would be a lot easier than mounting magnets for a Hall Effect sensor, and I was right.

But since you already mounted up your magnets, some Hall Effect sensors care about the magnet polarity, can be either North or South, and some work either way. I didn't notice if you said which sensor you were using. But verify what you have, and whether all the magnets are oriented the same way. Also the orientation of the sensor. I think I have one of those Sainsmart modules, and I don't remember getting any documentation with it, but I believe the flat face of the sensor has to point toward the magnet. Please don't be offended if that's how you set it up.

[Ralphxyz]

I had good success with an infrared "obstacle avoidance sensor" and six small pieces of reflective tape stuck to the tail end of my spindle.  Mounted the sensor 1/2" from the spindle and played with the angle until I got solid readings.  I figured it would be a lot easier than mounting magnets for a Hall Effect sensor, and I was right.

But since you already mounted up your magnets, some Hall Effect sensors care about the magnet polarity, can be either North or South, and some work either way.  I didn't notice if you said which sensor you were using.  But verify what you have, and whether all the magnets are oriented the same way.  Also the orientation of the sensor.  I think I have one of those Sainsmart modules, and I don't remember getting any documentation with it, but I believe the flat face of the sensor has to point toward the magnet.  Please don't be offended if that's how you set it up.

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I was getting a good signal at slow speed but it was lost at higher speed, it has been awhile since I played with this someday I'll get back to it.

Seemed like such a simple operation.

Ralph

[Briney Eye]

Forgive me again if you already know this, but you might want to check out this short video on the 'Tube. https://www.youtube.com/watch?v=4eqi0G7uY_4

Use a smaller magnet, though. I wouldn't go any bigger than 1/4".

[Ralphxyz]

Forgive me again if you already know this, but you might want to check out this short video on the 'Tube.  https://www.youtube.com/watch?v=4eqi0G7uY_4

Use a smaller magnet, though.  I wouldn't go any bigger than 1/4".

I have a led indicator when the magnet comes around so at slow speed I see it working.

But then the bluetooth connector decides to stop connecting so I can not use touchDRO.

It tries to connect and ether stays on "Connecting" or connects and immediately drops the connection.
I have tried rebooting but still the same.

I have had this problem before, it usually somehow rights itself.

Ralph

[Briney Eye]

My Bluetooth connection seemed sensitive to the type of wall wart I was using, and I tried a number of them from my junk collection before finding one that seemed to make things much more stable.  I also noticed that an LED lamp that I had in the shop was horribly noisy.  Changing it for a different one also made things quieter, along with adding decoupling caps in my scale read heads.  I eventually fiddled everything into being extremely stable.  I haven't noticed a hiccup in months now.

You haven't switched any shop lights to LEDs recently, have you?

[Ralphxyz]

You haven't switched any shop lights to LEDs recently, have you?

No big LEDs a couple of magnet based work lights.

I rebooted a couple of times now it works.

Seems like you have to use TouchDRO every day.

Ralph

[louthedog]

I had good success with an infrared "obstacle avoidance sensor" and six small pieces of reflective tape stuck to the tail end of my spindle.  Mounted the sensor 1/2" from the spindle and played with the angle until I got solid readings.  I figured it would be a lot easier than mounting magnets for a Hall Effect sensor, and I was right.

But since you already mounted up your magnets, some Hall Effect sensors care about the magnet polarity, can be either North or South, and some work either way.  I didn't notice if you said which sensor you were using.  But verify what you have, and whether all the magnets are oriented the same way.  Also the orientation of the sensor.  I think I have one of those Sainsmart modules, and I don't remember getting any documentation with it, but I believe the flat face of the sensor has to point toward the magnet.  Please don't be offended if that's how you set it up.

---

I was getting a good signal at slow speed but it was lost at higher speed, it has been awhile since I played with this someday I'll get back to it.

Seemed like such a simple operation.

Ralph

Success! I decided to buy one of those cheap "photo tachometers" to provide a reference.  In reality it appears that the Sainsmart module was working as it should have from the beginning. I put way too much trust in the dial settings of the lathe speed control. I didn't think the dial settings could be that far off but, in fact, they were.  The Touchdro/Sainsmart tachometer matches within 15-20 rpm of the photo tachometer. With this new-found knowledge I have re-adjusted the lathe DART controller to output closer to intended rpm. 

As I stated earlier, I used the Sainsmart Hall Effect module and milled a plastic ring that holds 8 evenly spaced neodymium magnets that are 5mm in diameter and 5mm thick.  This press fits over a shoulder on the spindle belt drive pulley. I fabricated a plastic mount for the Sainsmart module that allows the sensor to be rotated for proximity adjustment. The hall effect sensor itself is sensitive to magnet polarity but either side of the sensor can be used as long as proper magnet polarity is determined for that particular side. Using 8 magnets gave me a 15 rpm resolution. What I observed was using 1 magnet gives a 120 rpm resolution, 2 gives a 60 rpm resolution, 4 gives 30 and 8 gives 15.