Tachometer Kit

Hawkeye

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A while back, chollopeter posted a link to http://www.machtach.com/ It is a machine tachometer sold in kit form. I had seen it before, but the time was right for a reminder. Ron (Scrapmetal) had mentioned that he wanted to post a review of this product when he gets a chance. I'm not trying to scoop him, just add to the available info. I'm looking forward to Ron's review as well.

The package arrived around 3PM last Monday. Work has been short lately, so I was home to sign for it. The manual is available on the web site (but I haven't found it) and on the forum (but my registration hadn't gone through yet. There are two videos on the site - one on inventory and one on construction. The inventory one gave me all the part numbers and values, which was enough to build the tach. There has to be some advantage to two years of college-level electronics. :cool: Guy emailed me the manual after I had the unit assembled, which came in handy for the setup phase.

I set up in the kitchen so I could watch TV while I worked. Parts in trays, soldering station ready, boards in the rack and notes from the video in front of me.
P1010018.JPG

Resistors and capacitors in place. You start with the lowest parts and work up to the tallest.
P1010020.JPG

I opted for the 'half-size' version to make it fit into my control head. Here's the tach assembled and the two layers stacked. The standoffs didn't arrive with the kit, so I cut a few pieces of plastic tubing and bolted everything together with some 4-40 bolts, then soldered the wires in to connect the two boards together. The unit powered up exactly as shown in the construction video. A good sign.
P1010021.JPGP1010022.JPG

Here's the underside of the assembly, showing all of the components, and a shot of the choke (recommended for use with a VFD) wired into the power input. The cable running around the top goes to the optical sensor, which I managed to destroy shortly after mounting it. Make sure you plan for pulling out the pin when you'll be using back gears. :p Note the tips of the pliers in the second photo - notches ground into them to grip integrated circuit chips.
P1010023.JPGP1010025.JPG

Here's the relay module I made so that the correct machine would be displayed when I selected either mill or lathe on the VFD. I added a 9 volt regulator to it later, to drop my 12 VDC supply down to send power to the tach out in the control head.
P1010026.JPG

After doing in the optical sensor, I opted for the much smaller Hall Effect sensors, which meant mounting magnets on the spindles of both mill and lathe. You can't mount them on the spindle pulley on the lathe, since it doesn't turn at the same speed when you use back gears. I stuck them to the spindle nut and covered them with black tape.
P1010027.JPGP1010028.JPG

The Hall sensor is mounted on a bracket to the rear of the spindle.
P1010029.JPG

For the mill, I made up a ring of 3/16" ABS and pressed six magnets into pockets spaced at 60* increments, using the rotary table for accuracy. The ones on the lathe were optically spaced (eyeball).
P1010038.JPG

The Hall sensor was set in an ABS module and bolted below the spindle pulley. The cable is actually clipped to the metal pan and not rubbing on the pulley, as it seems to appear.
P1010041.JPG

It's really sweet to have the accurate RPM displayed on the VFD control head. You can also switch the tach to SFM mode and enter the tool or work diameter. This tach reads within 1 RPM of my laser tach, so the accuracy is good.
P1010030.JPG

I would highly recommend this tach to anyone who has any kind of speed control on his mill, lathe or drill press. It is easy to build and operate and has features designed for machining. If you aren't confident with your soldering skills, I recommend picking up a socket for the second IC chip, similar to the one provided for the main processor chip. The third 'IC' is actually a set of resistors in one package and would be hard to kill. And no, using a smaller torch won't help you solder the tiny parts. :lmao:

MachTach's principal, Guy Lopes, is a good person to deal with. He isn't trying to make money with this product, but is doing it for the love of the hobby. Actually, he was a moderator on this forum in the early days and still speaks well of this group.

P1010018.JPG P1010020.JPG P1010021.JPG P1010022.JPG P1010023.JPG P1010025.JPG P1010026.JPG P1010027.JPG P1010028.JPG P1010029.JPG P1010038.JPG P1010041.JPG P1010030.JPG
 
Mike
Nice job, and good write up and Pics
Im sure this will help others that are looking to install the same.

Good Work!

Paul
 
Hawkeye,

Thanks for the great post. I asked a stupid question on your VFD post before seeing this one. Sorry about that.

Benny
 
Hawkeye,
Thank you for the very informative review. I am looking forward also the the other review, Between the two just about anybody interested in a tach should be able to build one. I love saving money on DIY stuff, makes my meager budget go much farther.
Bob
 
two part epoxy would probably work well to mount the magnets..

I have a question, why use 6 magnets? could it be done with one or two magnets?
 
You can set the tach to use from one to 60 magnets, reflectors or slots. The more you use, the better the resolution. Epoxy wouldn't have been good on the lathe spindle nut because it would be hard to remove if I wanted or needed to service the spindle.
 
how do you set the tach to the number of magnets?

I have thought about adding one of the arduino tachs to my step pulley bridgeport thats running off a vfd.. I guess its about the same thing..
 
............. a shot of the choke (recommended for use with a VFD) wired into the power input.

............. I opted for the much smaller Hall Effect sensors, which meant mounting magnets on the spindles of both mill and lathe.

Hawkeye,

Thanks for taking the time to post. This looks like a great project to make the hobby more enjoyable. Just a couple of questions that I am not clear on.

Is the choke and the Hall Effect sensors options of the kit or an added refinement recommended by you. If added by you can you give more details for those of us not so electrically smart.

Benny
 
Great write-up. I bought the kit after that first post too. I've been debating where to mount it. Now, I know where.
 
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