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Tachometer sensor
#1
I've got one of the newer iGaging adapter boards, and I'm trying to add a tachometer to it.

The documentation says the tach needs an optical encoder with a quadrature output... Does this mean there's no way to use a regular Hall effect sensor with a magnet ring? I was really hoping to be able to use a Hall effect sensor on the machine this readout is on, as that would be the simplest method to implement.
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#2
So, a bit of testing, and I'm confused.

I purchased a cheap 6-pack of hall-effect sensors from Amazon, just to see if they work with this board. Right out of the bag, the answer is no.

I connected the sensor to the +3.3V and Gnd pins on the TouchDRO tach input, and connected the sensor signal output to the oscilloscope. The scope showed around 1.6v, which went to 0v when I put a small magnet near it.

The sensor PCBs have a little red LED on them. Reading about the touch probe input, it mentions that if there's an LED on the probe, it mush be reverse biased. So, I just removed the LED from one of the sensor PCBs, and soldered a 1k resistor across the pads. Now the scope showed 3.3v, which went to 0v when I put the magnet near it. I then used a drill with the magnet ring from my lathe, and the scope showed a crisp 0-3.3v square wave.

Yet, when I hook the sensor wire up to the TouchDRO board, and run the magnet ring by it, I get no RPM reading. I even tried removing the resistor and just shorting the LED pads together, with the same result.

I'm sure I'm missing something, but I'm not knowledgeable enough in electronics to figure it out. Any guidance would be appreciated.
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#3
Not making any headway.

Any help with sensor selection and wiring would be much appreciated.
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#4
With my TouchDRO iGaging adapter board, I tried the Arduino hall-effect sensor board without any luck, even tried some working hall sensors by themselves that I had from other projects.

What worked for me was to use a OPB704 reflective optical sensor.  I wrapped a piece of black plastic electrical tape around the back end of my lathe spindle, with a couple of evenly spaced gaps in the tape to expose the shiny spindle to the OPB704.  The sensing distance is 3.8mm so it was very easy to adjust.


[Image: OPB704-module.png]

[Image: OPB704-schematic.jpg]

Rick
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#5
Awesome. Thank you!
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#6
Ok, so I finally got a chance to try the photosensor, to no avail. I've got it wired exactly as shown, but I'm not getting an RPM readout. My oscilloscope shows a square-ish wave... the sides aren't perfectly vertical on the rising or falling edge. I'm seeing a steady 3.3v at rest, and it dips back to zero when the sensor sees a reflective surface.

Maybe my board is messed up? I feel like this shouldn't be this difficult.
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#7
(04-12-2021, 03:43 AM)MidniteMachinist Wrote: I feel like this shouldn't be this difficult.

A thought occured.... have you enabled the tacho in settings ?
I am still waiting on one of my scales and have just recieved my board, so havn't had any play time yet!! But a tacho is the next one on the list.
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