# tachometer, the easy way



## canadianhorsepower (Jan 20, 2019)

I'm a big fan of tachometer on any machinery. But on the other hand it irritates me
when you look at a tachometer on some machinery site and the price is exhaustive. and for NO real reason.
here are pictures of the tach system I use, from 9 to 99000 rpm, from 9 to 36 volts and can be mounted
in 1/2 hour price $13.00 CAD. the only thing missing is a plastic boxe $3.00. enjoy the pictures.
and YES my lathe is mounted slanted a bit. lollll


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## chucketn (Jan 20, 2019)

Luc, is that a commercial unit, or did you build it?


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## canadianhorsepower (Jan 20, 2019)

chucketn said:


> Luc, is that a commercial unit, or did you build it?


 all I did is installing it, here is the link

https://www.banggood.com/4-Digital-...l?rmmds=home-right-flashDeal&cur_warehouse=CN


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## chucketn (Jan 20, 2019)

Thanks for the link, Luc. I need to find something to put one on!


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## RM-MN (Jan 21, 2019)

Thanks for the link.  I have a tractor whose gauges have gone bad and the gauge cluster is quite expensive.  I may replace the entire cluster with digital readouts now that I have seen what is available and the cost compared to OEM including the tach, fuel, engine temp, and hour meters.


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## DickInOhio (Mar 8, 2019)

canadianhorsepower said:


> I'm a big fan of tachometer on any machinery. But on the other hand it irritates me
> when you look at a tachometer on some machinery site and the price is exhaustive. and for NO real reason.
> here are pictures of the tach system I use, from 9 to 99000 rpm, from 9 to 36 volts and can be mounted
> in 1/2 hour price $13.00 CAD. the only thing missing is a plastic boxe $3.00. enjoy the pictures.
> ...


 
OK I purchased this kit and it had no wiring instructions. how did you wire yours. thanks dick


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## canadianhorsepower (Mar 9, 2019)

HI Dick
if you look at the sensor it has a sticker that says BROWN + DC 6-36V you would tie this to a 9 volts battery and the positive of your
RPM meter on the positive side of the battery
one says BLUE - you would tie this with the negative wire of your RPM meter to the negative side of the battery.
the last one BLACK would be tied to the signal input of your RPM meter
this will turn your meter on.
now if you flash a small magnet close to the sensor the reading will change
good luck


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## nel2lar (Mar 9, 2019)

Smart phone or android, there is an app for tachometer. No wires, No holes, nothing just a piece of masking tape and the app. Love it because my phone is always near to me.
Nelson


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## canadianhorsepower (Mar 9, 2019)

nel2lar said:


> Smart phone or android, there is an app for tachometer. No wires, No holes, nothing just a piece of masking tape and the app. Love it because my phone is always near to me.
> Nelson


sorry but I usually don't carrey my phone in my pocket with my hand full of oil or grease to check   my
lathe, drill, mill RPM when i'm working


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## DickInOhio (Mar 10, 2019)

canadianhorsepower said:


> HI Dick
> if you look at the sensor it has a sticker that says BROWN + DC 6-36V you would tie this to a 9 volts battery and the positive of your
> RPM meter on the positive side of the battery
> one says BLUE - you would tie this with the negative wire of your RPM meter to the negative side of the battery.
> ...


Tank you very much


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## Noitoen (Mar 10, 2019)

For a quick rpm sensor you can use a small dc motor as generator. A potenciometer to calibrate and a voltmeter is all you need. Dc motors generate a voltage proportional to speed


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## canadianhorsepower (Mar 10, 2019)

yes but do you realize the amount of work involve


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## canadianhorsepower (Mar 10, 2019)

DickInOhio said:


> Tank you very much


can you post pictures of final  step and how you like it
Thanks


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## velocette (Mar 11, 2019)

Nice and neat setup puts my " Heath Robinson" effort as rather antiquated.
Diesel Engine Tachometer, 96 tooth disc fitted to spindle pulley, read with a Volvo ABS brake sensor, 12 volt power supply.


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## comstock-friend (Mar 11, 2019)

Luc, kit says it doesn't come with the magnet. What are you using for the magnet, a plain cheapy (refrigerator magnet) or rare earth??? Mounting for magnet; drilled and glued in or something else???

Calibration: this would seem to be nuts on as I assume it is counting every time the magnet passes. Is the signal and sampling rates correct that it doesn't drop the count? Thinking of putting one on my Tormach PCNC 1100, as the tapping cycle has to have the spindle close enough that a tension compression tapper won't over feed... Comments?

John


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## peter2uat (Mar 12, 2019)

I mounted this sensor - *LJ12A3-4-Z/BX* – which is not Hall-effect but inductive (coil and amplifier), which has the same cable layout, and comes as a 60 x 12mm screw-mounted assembly. Nice effect here is a red/orange LED at the other end of the sensor, which blinks at low RPM. The size of this sensor can be reduced to 35 x 10mm Ø by removing the aluminum cover – part of the electronics is deep set into epoxy - BUT isolate the rest of the electronics by filling up with epoxy too. The LED may then be mounted more user friendly (or omitted). I milled a small housing to mount this into the gear cover of my mini lathe, made a bracket to carry the display, and now I am very happy with it. It takes a second to display the right RPMs, that is OK with me.
The magnet is a piece broken off of a hard drive magnet (1/4 x 3/8" or so) glued to the spindle with CA.
The display is one of those cheap ($13) ones from the bay or ali..., a small wallplug for 12V/1A DC and a small plastic box (from a defunct PSU) and two cables and you are up and running. I since removed the LED from the sensor as it was distracting and of no real use for me.


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## canadianhorsepower (Mar 12, 2019)

comstock-friend said:


> . What are you using for the magnet, a plain cheapy (refrigerator magnet) or rare earth??? Mounting for magnet; drilled and glued in or something else???John


I'm using a rare earth magnet, only because it can be mounted farther from the sensor.
I didn't even glue mine ,close fit hole and a light press fit. this picture is from my drill press with the same set up.


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## Jackham (Apr 11, 2019)

Hi guys, thank you for sharing your awesome pictures. Looking at the pictures of Luc's and Peter's lathes they have both DROs mounted on the axes. Wouldn't it be more comfortable mounting all DROs including the tachometer in one place? This way you wouldn't have to turn your head while viewing each axes or the spindle rpm.


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## peter2uat (Apr 11, 2019)

I had those readouts on both lathe spindles but got rid of them ASAP - the batteries were draining in no time, the readout windows got burned from hot chips and the backlash could not be eliminated. AND the new spindles were imps and not metric so I got rid of the crap.
RPM I do not watch after I set the speed.
There are some DROs on aliexpress wich can do RPM too, but are very expensive ($ 335 or more, with LCD screens) so I do not consider them to be a solution for a smal hobby lathe. The new iGaging EZ-View DRO system has a more reasoable price ($ 129 with 3 magnetic scales on ebay)
I have added the wiring diagram to the sensor/display I have shown above.


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