Lathe Tachometer

[modeldozer]

Hi all mad modders.

I wanted to add a tachometer to my 7x12 lathe.  After a bit of research I ordered a digital panel mount frequency meter of the bay.
As frequency is pulses per second I had to make a plan to get 60 pulses for every turn of the spindle so the meter will directly read RPM.
Decided to make a counter wheel with 60 holes mounted between the nuts on the spindle.

Made a quick indexer using one of the lathes change gears.



And used it to drill 60 1.2mm holes in a steel disc.



This was mounted on the spindle and an optical sensor was mounted on a bracket to the headstock.





I built a extension box that fit to the front of the lathe controls to house the meter and a supply that was salvaged from a mobile phone charger.







The meter works great and was tested with reference to a handheld tacho and reads within 1 or 2 RPM.

Cheers.

Abraham

[Chuck in E. TN]

Nice job, Abraham.
Chuck

[Swarfing]

Good job Abraham, could you tell us more bout the connections an the relation between the 60 holes and frequency etc.

Thanks

Paul

[Fredbare]

Excellent modding, thanks for sharing.

John

[John Rudd]

Spindle speed is revs per minute.... so if your spindle turns at 3000 rpm that equals 50 Hz...or 50 pulses per second.....3000/50 = 60 hence the number of holes needed for the opto coupler...


Nice job..I ought to get round to finishing the 4 I 'built' for my two lathes and 2 mills     

( built = 1 plastic box with 4 magnets in bottom and hole cut out to take the panel meter, add a bit of wiring and lash up to machine      )

[modeldozer]

Thanks to all for their comments.
As frequency is pulses per second and there are 60 seconds in a minute, to convert to per minute it needs to get 60 pulses per revolution.

The opto sensor is wired as in the attatched diagram.

Abraham

[Swarfing]

Thanks guys, i thought that might be the case but nice to check.

[modeldozer]

Hi All,

Had some requests for the pcb layout for the picup, so here they are. (eagle V6)

Cheers
Abraham

[saw]

Nice done 

[slowcoach]

Hi, Which Fleabayer did you get the Tacho display from?

Cheers
Rob 

[John Rudd]

I got mine........


http://www.ebay.co.uk/itm/RED-LED-PANEL-DIGITAL-FREQUENCY-SPEED-REVOLUTION-METER-GAUGE-COUNTER-TACHOMETER-/400465472257?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item5d3d9a2b01

[Meldonmech]

Hi Abraham,
                    What a very neat job you have made, it looks like it has always been part of the lathe.

                                   Well Done            Cheers David

[modeldozer]

Thanks for the kind comments guys.

Got mine from
http://www.ebay.co.uk/itm/9999Hz-Universal-High-Quality-Digital-LED-Frequency-Wave-Meter-Panel-055-/370646469129?ssPageName=ADME:L:OC:ES:3160

Cheers
Abraham

[John Rudd]

That's not a bad price to pay either inc free postage...Think I paid around £13 for one of the ones I won (auction style)...Might buy some more..
The tacho's I got are  based around a microcontroller rather than the two chips in the foto of yours Abraham...Not that it matters so long as they work..