RPM Counter connections

[Neil WyattModerator @neilwyatt]

Posted by Douglas Johnston on 16/11/2015 10:46:49:

I now see how the thing is connected up apart from one thing. Some people have the set up working without a pull up resistor from the black lead on the sensor to the positive power connector, so should the resistor be included or not?

Doug

It depends, assuming the Hall Effect has an open collector output (most do) a pull up is required, but these days 99% of microcontrollers have switchable internal pull ups on their inputs that can do the job. But these might not be enabled…

So in short, it depends, but adding one is unlikely to do any harm.

Neil

[Enough!Participant @enough]

There is a YouTube video concerning one of these tachs. At about 3 minutes into this video he shows a page to the camera which contains a wiring diagram. If you pause the playback at this point, hit PrtScn, then do a paste into …. whatever (graphics program, Wordpad, Word etc) you can retain a readable copy …. probably best to make the video full-screen first.

I wired mine according to this simple diagram and it worked fine for at least my version.

[John Stevenson 1Participant @johnstevenson1]

Connected mine up today.

Red on display connected to brown on sensor – both to 12v+

Black on display connected to blue on sensor – both to 12v-

Yellow on display connected to black on sensor.

Magnet stuck on cordless drill chuck, must have been lucky on which way as it all worked first time, no resistors or nothing.

This is a blue display BTW.

[Kevin Monks 1Participant @kevinmonks1]

Hi all,

Quick Intro: Self-Employed welder/fabricator from Sunny Dorset. Like to do a bit of machining too. I own a Beaver model A milling machine, which I an in the process of re-assembling after 3 years of being in bits.

Just a quick Thankyou for the information in this thread. I just bought the afformentioned rev counter (for my mill) at the begining of the thread and came across this during my google search for information to wire it up.

All sorted now, no more head scratching.

Cheers all.

[Colin LLoydParticipant @colinlloyd53450]

I've got one of these to work with a 10mm dia x 10mm long high strength neodymium magnet (specification says these can lift 3.5kg) fitted to the spindle locking ring on top of the mill. As Howi says, even at 2500 rpm on my milling machine – the magnet doesn't move and I can have the sensor nearly 10 mm away from the magnet without loss of signal.

But I suspect from a cursory look at the subject of the Hall Effect and general magnetic field effects that a strong narrow vertical magnet would provide better precision for the sensor response – in that the effect would be a quick "on-off" as apposed to the "rise & fall" that the wide magnet would give. And again – I'm guessing – at high RPMs, with the magnet width being a substantial part of the overall circumference, the sensor might not have returned to it's "Off" state before the next revolution brings the magnet into its sphere of influence.

Perhaps someone with a better grasp of Hall effect proximity sensors than me could put me straight.

[mtrehy mtrehyParticipant @mtrehymtrehy33968]

HI,

Would be very grateful for some help with this…. I have bought one of these and attached it to my bridgeport. It seems to behave very strangely. I have placed it on top and added a bit of hex bar at the end of the drawbar – hex is 30mm AF and I have attached the magnet on one of the corners of the hex so it's probably on a 35ish diameter….

The bridgeport has VFD.

The rpm readout either jumps all over the place or doesn't read at all (—-). It was slightly better but not perfect if I move the display a long way from the mill (I was suspecting some kind of interference). Doesn't make any difference whether the spindle is fast or slow. If I have the mill off and turn the spindle by hand it seems to read ok. If I try to replicate that speed with the slowest the mill will go it still plays up.

Can the sensors and/or unit be affected by interference from the VFD? Apologies if this is a stupid question but it's not my area of expertise. Will the 30mm (approx) diameter of the magnet mounting be enough or does it need to be on a bigger disk?

Any help greatly appreciated!

THanks

[Neil WyattModerator @neilwyatt]

Have you tried reversing the magnet?

A picture would help us understand your setup.

Neil

[Mike PooleParticipant @mikepoole82104]

Is it possible the hexagon is behaving like a six weak poles? Try as an experiment putting it on a circular surface to eliminate the possibility.

Mike

[mtrehy mtrehyParticipant @mtrehymtrehy33968]

I'll get some pics tomorrow. I tried magnet both ways and not a massive difference either way.

Brass hex so I assume not possible to create any issue….

[Mike PooleParticipant @mikepoole82104]

Posted by mtrehy mtrehy on 14/10/2018 18:48:30:

I'll get some pics tomorrow. I tried magnet both ways and not a massive difference either way.

Brass hex so I assume not possible to create any issue….

Oh well that shot that idea down in flames, to eliminate the VFC noise possibility could you lash it up on another machine with a conventional drive?

Mike

[mtrehy mtrehyParticipant @mtrehymtrehy33968]

Managed to sort it out. Was definitely interference. Removed the sensor cable and twisted all 3 wires together, wrapped them in aluminium foil and then back in the sleeving and it now works perfectly.

Thanks for all the replies.

[petro1headParticipant @petro1head]

Sorry to resurect however I have just wired up one of these and this is the output.

Somethings wrong – Video

[petro1headParticipant @petro1head]

Posted by petro1head on 10/12/2019 13:51:37:

Sorry to resurect however I have just wired up one of these and this is the output.

Somethings wrong – Video

Sorted, I took a 10v supply from the VFD which was not a good idea. Now using a std 12v power supply and all is well

[Mike Palmer 1Participant @mikepalmer1]

This little bugger is driving me up the wall, I connected as diagram on back of display switched on and got display with numbers on and thought all is well, but when I ran the spindle no numbers just display showing zeros. Removed the sensor from machine and tried waving magnet across sensor but no joy.

Played around different combination of connections but still no numbers.

Reading the above posts there seems to be a question on pin 2, should it be connected to ground? I have tried this but to no effect.

Anyone got thoughts!

Thanks

Mike

[JasonBModerator @jasonb]

It's the negative of the power supply not Ground as in Earth.

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