Tachometers

[Rauce]

I’m interested in adding tachometers to some of my tools since I have variable speed drives on everything.

I have bought and tried the cheap Hall effect ones and not been overly impressed.

Found a product called the Tachulator that makes them with optical sensors and both with and without a built in SFM calculation feature. There are a few resellers in the states like http://www.mkctools.com/tachulator.htm and little machine shop. I was surprised to find with some digging that they are made in Toronto by http://www.trexon.com/ .

Has any one bought or seen one in person before? I emailed the address on the trexon page but didn’t get a response.

 

[Susquatch]

Nothing, but interested in knowing what you find.

@whydontu out in BC has done some awesome work with an Arduino. @YYCHM has already implimented some of the concepts.

Thread 'Bridgeport Mill Tachometer' https://canadianhobbymetalworkers.com/threads/bridgeport-mill-tachometer.3986/

The thread covers some of the issues and might explain your experience. Like so many digital systems, the numbers depend on the programmer who may or may not have a clue about what's really going on or how to make it work.....

Lots of other info on the forum. Try searching on "Tachometer Arduino" on the forum.

My DRO has the hall effect system built in. But no SFM. I am still thinking I'll make my own. I have very little faith that they did it right. (running average, missing counts, filtering, programmability, etc

 

[Mcgyver]

Good topic. I looked at the unit in the link, how does SFM work when there is no keyboard to input the diameter?

What didn't you like about the hall sensor types?

I like the idea of a tach, but think maybe SFM is a bit gimmicky.....even if you could enter dia, its so quick to do rpm=4*CS/dia in your head I probably couldn't be bothered constantly punching in a dia.

 

[Rauce]

Good topic. I looked at the unit in the link, how does SFM work when there is no keyboard to input the diameter?

What didn't you like about the hall sensor types?

I like the idea of a tach, but think maybe SFM is a bit gimmicky.....even if you could enter dia, its so quick to do rpm=4*CS/dia in your head I probably couldn't be bothered constantly punching in a dia.

From what I can tell the knob is also a push button, so you push to switch modes to the input function and then turn it to dial in a diameter.

I agree that it’s a bit gimmicky, I definitely wouldn’t bother with the SFM version on my drill press and could easily live without it on my lathe and mill.

My Excello has the variable speed pulley system and I rarely change speed at the VFD. The displayed speed on the machine head is accurate enough.

What really got me thinking about this is the incoming hendey lathe. Other than the back gear all speed control will be from the motor/drive so a tachometer would be handy. I could of course make a chart of RPM at spindle vs. Drive frequency to reference but it would be nice to just have a display. I still have a $25 Amazon Hall effect thing but I was hoping there was a better plug and play option that I would trust more. Making a custom mount/enclosure is fine but I’d prefer not to mess with electronics or programming.

 

[Mcgyver]

What really got me thinking about this is the incoming hendey lathe.

So you did the deal? Right on. Glad to have been the matchmaker on it

 

[Rauce]

Nothing, but interested in knowing what you find.

@whydontu out in BC has done some awesome work with an Arduino. @YYCHM has already implimented some of the concepts.

Thread 'Bridgeport Mill Tachometer' https://canadianhobbymetalworkers.com/threads/bridgeport-mill-tachometer.3986/

The thread covers some of the issues and might explain your experience. Like so many digital systems, the numbers depend on the programmer who may or may not have a clue about what's really going on or how to make it work.....

Lots of other info on the forum. Try searching on "Tachometer Arduino" on the forum.

My DRO has the hall effect system built in. But no SFM. I am still thinking I'll make my own. I have very little faith that they did it right. (running average, missing counts, filtering, programmability, etc

Maybe you or someone else knows more but a lot of the equipment I deal with at work (turbines/compressors) have stand alone tachometers or sensors wired in to a PLC or similar control system. Typically we physically install this stuff but some control tech at site takes it from there. These have a non contact sensor positioned near a toothed wheel. No magnets, not optical as far as I can tell. It seems having a pick up wheel with multiple positions would yield greater accuracy right? The trexon device is optical but gives you option of multiple pick up points per rotation.

 

[Rauce]

So you did the deal? Right on. Glad to have been the matchmaker on it

Haven’t picked it up yet (scheduled for next Friday) but yeah I’m commited!

 

[Susquatch]

Maybe you or someone else knows more but a lot of the equipment I deal with at work (turbines/compressors) have stand alone tachometers or sensors wired in to a PLC or similar control system. Typically we physically install this stuff but some control tech at site takes it from there. These have a non contact sensor positioned near a toothed wheel. No magnets, not optical as far as I can tell. It seems having a pick up wheel with multiple positions would yield greater accuracy right? The trexon device is optical but gives you option of multiple pick up points per rotation.

My goto reference for such things nowadays is the crankshaft position sensor in a modern engine. Not only do they know the RPM very accurately, but they also know the exact position in each revolution as well as the rate of change of rpm (accelerating decellerating, etc etc.

They typically use a sort of hall effect sensor that actually counts gear teeth in a ring gear as well as a special syncing tooth to keep everything accurate. I'd bet big bucks that's what you saw for turbines.

The problem here is speed. If the device measuring the speed isn't order's of magnitude faster than the devices it is measuring, the whole house of cards crumbles. That is why I wanted to directly access the timer registers in the Arduino. I just have not had time to do it. And at the rate that time is flying by, I may never do it.

It's not that I don't have the time or the knowledge. Instead, it's all about priorities. My first priority is a working dro on my mill, then my farm gps navigation system that I need working before May, then then then. Someday I'll get to the tach. In the meantime, as others have said, it is not essential.

As @Mcgyver says, the sfm number is ridiculously easy to do. And if not, there are websites, calculators, and graphs that make it even simpler. So it's not a real big deal or a show stopper either way.

In the thread I referenced above, @whydontu got it working acceptably with an Arduino.

 

[ShawnR]

Maybe you or someone else knows more but a lot of the equipment I deal with at work (turbines/compressors) have stand alone tachometers or sensors wired in to a PLC or similar control system. Typically we physically install this stuff but some control tech at site takes it from there. These have a non contact sensor positioned near a toothed wheel. No magnets, not optical as far as I can tell. It seems having a pick up wheel with multiple positions would yield greater accuracy right? The trexon device is optical but gives you option of multiple pick up points per rotation.

I think they would be using proximity sensors. They sense the steel. The tooth triggers it whereas the space between the teeth does not (yes, that sensitive) Doing it this way, dropping a pulse or two or 10 will not adversely affect the signal. Then, in the programming, the tooth count is divided out. Very nice but a little elaborate for the home shop, although, with an arduino, not hard to do at all. I don't know the cost of the sensors good enough to do this but with technology, they might be cheaper than I think

I had to research a bit. Something like this what I am guessing they use for the installation as you describe

Sensor

 

[Susquatch]

I think they would be using proximity sensors. They sense the steel. The tooth triggers it whereas the space between the teeth does not (yes, that sensitive) Doing it this way, dropping a pulse or two or 10 will not adversely affect the signal. Then, in the programming, the tooth count is divided out. Very nice but a little elaborate for the home shop, although, with an arduino, not hard to do at all. I don't know the cost of the sensors good enough to do this but with technology, they might be cheaper than I think

I had to research a bit. Something like this what I am guessing they use for the installation as you describe

Sensor

A crankshaft position sensor is a LOT cheaper. Extremely high volume part. Dead nuts reliable too.

A-Premium Crankshaft Position Sensor Compatible with Hyundai Accent Elantra Coupe GT Tucson Veloster Kia Forte Koup Rio 2012-2019 Soul 2010-2019, Crankshaft Position - Amazon Canada

A-Premium Crankshaft Position Sensor Compatible with Hyundai Accent Elantra Coupe GT Tucson Veloster Kia Forte Koup Rio 2012-2019 Soul 2010-2019 in Crankshaft Position.

www.amazon.ca

 

[ShawnR]

Damn! Another project!

Quit doing that @Susquatch !!

 

[DavidR8]

I’m interested in adding tachometers to some of my tools since I have variable speed drives on everything.

I have bought and tried the cheap Hall effect ones and not been overly impressed.

Found a product called the Tachulator that makes them with optical sensors and both with and without a built in SFM calculation feature. There are a few resellers in the states like http://www.mkctools.com/tachulator.htm and little machine shop. I was surprised to find with some digging that they are made in Toronto by http://www.trexon.com/ .

Has any one bought or seen one in person before? I emailed the address on the trexon page but didn’t get a response.

I emailed the Tachulator reseller but haven't received a response.

 

[whydontu]

Tachulator seems reasonable on price, maybe double the cost to build mine.

Most expensive single component was the 5”x5” electrical box.

Mine uses an IR optical sensor counting holes in a punched disc attached to the quill. The Arduino code measures time between successive pulses, averages out the value after seven pulses, and displays the results. Two dials set cutter diameter and material. This is used to calculate recommended RPM and SFM. The tachometer calculates actual running SFM from RPM and cutter diameter.

Top two lines are current, bottom two lines are reference book values.

 

[DavidR8]

Tachulator seems reasonable on price, maybe double the cost to build mine.

Most expensive single component was the 5”x5” electrical box.

Mine uses an IR optical sensor counting holes in a punched disc attached to the quill. The Arduino code measures time between successive pulses, averages out the value after seven pulses, and displays the results. Two dials set cutter diameter and material. This is used to calculate recommended RPM and SFM. The tachometer calculates actual running SFM from RPM and cutter diameter.

Top two lines are current, bottom two lines are reference book values.

Did you write the code yourself?

 

[whydontu]

Cobbled together from this. My programming skills are best described as brute force with zero elegance.

I added code to read two pots and select material and sfm values from a simple lookup table, then use these values and a bit of math to calculate the display text.

A real programmer could probably write it better, but my hack works so it’s Good Enough.

Easy Arduino Tachometer

Build your own tachometer with an LCD display to check some RPMs.

www.pyroelectro.com

 

[DavidR8]

Cobbled together from this. My programming skills are best described as brute force with zero elegance.

I added code to read two pots and select material and sfm values from a simple lookup table, then use these values and a bit of math to calculate the display text.

A real programmer could probably write it better, but my hack works so it’s Good Enough.

Easy Arduino Tachometer

Build your own tachometer with an LCD display to check some RPMs.

www.pyroelectro.com

Thanks! I have an Arduino sitting around looking for a project so...

 

[chip4charlie]

LMS sells the Tachulator: https://littlemachineshop.com/products/product_view.php?ProductID=2658&category=

 

[SomeGuy]

Not that this is what you're looking for, but as a cheap "check the RPM" thing...these do work:

Amazon.ca

Worth grabbing if this isn't something you're too worried about all the time (like if a few key marks on your speed dial would get you close enough).

 

[Rauce]

LMS sells the Tachulator: https://littlemachineshop.com/products/product_view.php?ProductID=2658&category=

Yeah that’s where I saw it first. If I can get it from the manufacturer that would be better than buying from the US.

I do have a princess auto optical tach like that Amazon one, but it would be nice to have something permanently fitted to the lathe.

 

[DavidR8]

@Rauce I just received a reply from Trexon:


Hi, David:-

Tachulator is 115.00 + 10.00 shipping + 5% GST (BC) = 131.25 CAD
including sensor.

Payment can be by Paypal or Interac to this e-mail.

It would take a couple days to finish off your unit. Please let
me know if you would like to go ahead.

Best regards,
--sp

I might go for this option...