mill spindle speedo..

[stirling lad]

Has anyone fitted one of these tachometers to their mill?

http://www.ebay.co.uk/itm/4-Digital-Tachometer-RPM-Speed-Meter-Red-LED-Proximity-Switch-Sensor-NPN-/311016646077?pt=

If so could they please explain how its done to me as i've ordered one but don't know what else i'll need to buy to get it working...do i need one of those transformer things often used on other electrical things,,, you know the ones'' they look like large phone chargers...

or is it going to be more complicated than that?? in which case i should abort this idea now,, as leccy and me don't go well together...

[awemawson]

I think you'll find Norman V has fitted one to his home made mill described in the thread cited below. I have the kit here in a jiffy bag on my desk waiting for an opportunity to fit it.


http://madmodder.net/index.php/topic,9592.0.html

[John Rudd]

Dont wanna rain any anyones parade, but I found the refresh rate of these Chinese displays to be a bit on the slow side....Mebbe I was expecting too much

[awemawson]

Just dug mine out of the bag and connected it. Very simple. The display has a 3 wire lead, clearly labelled on the board by the connector as 12v (Red) 0v (Black) and sensor input (Yellow). There is a proximity sensor again with three leads Blue (0v) Brown (12v) and Black (sensor output)

Connect the board and the sensor together:

Black to Blue (0v)
Red to Brown (12v)
Yellow to Black (Sensor output)

Then connect the 0v and 12v to a 12v DC source (1/2 amp should easily do it) and off you go.  As John says the refresh rate is rather slow but if the mill is running at a constant speed that doesn't matter.

The proximity sensor can detect a largish hole or a stud sticking out so long as they are steel or iron.

[John Rudd]

Yup as Andrew says, they are easy to install, although mine uses an opto coupler of the slotted type for triggering...
Works well in my mini lathe...I have another 3 to fit to my other mills/ lathe.....Another roundtoit job

[stirling lad]

John,  Andrew,,
thanks  for your quick replies,,,
So you reckon it's do-able even for an electrophobe like me... thats encouraging...
It says=detected objects- magnet. so would i just fit one of those neodymium magnets somewhere on top of my pulley with the sensor facing it and just bring it in closer until the sensor picks it up?  or does it mean the sensors magnetic and i have to put a piece of ferrous metal on top of the pully..?

..m.

[John Rudd]

My interpretation is that the probe detects the presence of a magnetic body, in which case you will need to attach a magnet to the main spindle pulley, then mount the probe in such a fashion that it can be adjusted in relation to the magnet...
I asssume the display units counts rpm's based on one pulse per rev? Else you would need more than one magnet..

[chipenter]

I have one and the sensor is magnetic and will detact iron , so iff your pully is ally fit a peice of steel or drill a hole if the pully is steel , two magnets will only work up to about 900 rpm on mine .

[John Rudd]

From the sellers bumf...
-Hall proximity model:NJK-5002C .
-Detected objects: Magnet.
-Detection range: 1mm-10mm.
-Proximity output current: 20mA(For the sensor).
-Operating temperature: -10 to 60°C.
-Sensor wiring:brown(Power+),blue(Power-),black(signal).
-Sensor size: 37 x 12 x 10mm.


So, needs a magnet....
Try it, what have you to lose? Either works or not....

[awemawson]

Read Normans thread - it does not need or want a magnet as such, just what is is detecting needs to be able to be attracted BY a magnet. A simple hole or sticking out bolt head will do fine.

[John Rudd]

But its a Hall sensor... Not a proximitor.....

[Arbalist]

Read Normans thread - it does not need or want a magnet as such, just what is is detecting needs to be able to be attracted BY a magnet. A simple hole or sticking out bolt head will do fine.

Yes, quite right. Normans was a proximity sensor so no magnet required. In fact when he tried a magnet it didn't work. 

[John Rudd]

Well whatever it is, so long as Norman has it working thats all that matters here....,
But, the ebay link he provided links to a display with Hall sensor, thats what the descriptions reads, bur then the seller could be wrong....

[awemawson]

Mine is like the original link and is a PROXIMITY sensor. The central core is a magnet with a coil wrapped around it, and it has internal electronics to detect the flux changes in the coil created by external magnetically susceptible material passing close by

[John Rudd]

Ahh.... The light has come on!

Got confused by the op and the thread by Norman....

Ermmm.....I'll dip out on this....

[NormanV]

I'm late to join the party.
It does not need a magnet, in fact it reads the hole that I made for the magnet perfectly well, it's about 5mm deep 10mm dia. The refresh rate is not good, when I stop the machine the readout always shows a number but when I restart it immediately gives a correct reading.
I am very happy with it, terrific value for money.
Be aware that it is very sensitive to the distance between the sensor and the hole.

[stirling lad]

Ahh.... The light has come on

Haha,, my light had come on but went back out again about 3or4 posts ago ...

as long as i can get it powered i'll just try it with and without a magnet...

Norm, it does seem like really good value for money...

thanks for all your advice gents, hopefully this will make life a little easier as i really don't have the experience of milling machines to guess with confidence how fast they are revolving ...

...M...

[stirling lad]

oops,,

   i'll never get the knack of these 'quote ' thingy's....

..m..


(Now sorted for you, Mike).
David D

[dawesy]

Well I've ordered one for my lathe.  The original motor turned out to be 4 pole after I'd already brought a 2 pole. So this will be good for working out the spindle speed.

[stirling lad]

 you were'nt kidding when you said they are easy to fit...
I managed to get one working and if i can anyone can....
...mike..

[Stilldrillin]

you were'nt kidding when you said they are easy to fit...
I managed to get one working and if i can anyone can....
...mike..

Well done, Lad! 

David D

[awemawson]

  excellent 

[John Rudd]

Good to hear you finalky sorted it...

[PJW]

I have just ordered one of these, they seem inexpensive & well worth a try!

Peter

[Manxmodder]

There have been a couple of posts saying the refresh rate was rather slow on these units.

What sort of time are we talking,10 seconds or is it more?

....OZ.

[stirling lad]

 

  No Oz, It's about half a second... if thats too slow for some folks they ought slow down a little an smell the flowers..haha..

  ..mike.

[PJW]

Mike your inbox is full & I cant send a message to you!