using hall proximity sensors with tachometer

[GK1918]

So your able to measure faster speeds than 1400RPM? Are you just using the magnet they sent with the sensor?
I'm mounted around 1mm or so but I didn't measure like you did. I will try setting with feelers like you did and see if it get any better.

BTW; I had downloaded the Machtach manual (even though I didn't want to buy one of their tachs) to see if they had any info I could use about the sensors. I also did some searching for other info online about the switching frequency of sensors. The original hall effect sensors have a frequency of 320kHz and the new one they sent, the inductive sensor is only 0.5kHz. Somehow I did feel that the frequency was part of the problem. By my thinking, 320kHz is 320,000 pulses per second so It should be more than fast enough, right?

I guess all I can say is the price was right. And as far as 1400 rpm that I dont know. I usually run around 800 rpm and the magnet has not
flown off 'yet'. The magnet is on the circumference of the spindle timimg belt pulley. The instructions are horrible it was all guess work
on my part. My first one blew up using 12vt transformer I left a note with ebay seller and ordered another and then they sent me two
(one for free). This time i used a 9vt battery with a push button switch. Its only needed when changing belts anyways.

 

[iron man]

Another Update:
The new inductive proximity sensors arrived from the seller and I gave them a try. They sense iron versus magnets. The results got worse. This time the display maxed out at around 350 rpm before it stopped picking up. So the "engineer" the ebay seller has seems to know about as much as I do about this problem.

As you could see from my previous picture with the original sensors I had been placing the magnets on the perimeter of the ring and only got to about 950-1000 RPM, I decided go back and try the original sensors and place the magnets on the top surface versus on the perimeter. With this change I actually hit about 1450 RPM now before it stops reading. Much improved but something still not right. I even tried increasing the magnet thickness to see if that would help pick up at higher speeds, no change.

Since the digital tach is really more of a novelty I've about reached my limit for dealing with this and scrap the whole idea.

I have used the sensors to pick up iron I used a steel gear and it worked fine what did you use?? The hall effects sensor has to be the right one for high speed I use to use for engine tach's.. Ray

 

[oldplanecollector]

I have used the sensors to pick up iron I used a steel gear and it worked fine what did you use?? The hall effects sensor has to be the right one for high speed I use to use for engine tach's.. Ray

With the inductive sensors I took the plastic ring I originally made with magnets on the perimeter and trimmed down to remove magnets and tapped in a couple #10 hex heads on perimeter.

After reading some online info about the magnetic sensors I question if it would need an even stronger magnet to read at higher RPM. Either way I'd really have to have at least 2 opposed magnets to keep it balanced. My last run at 1400 RPM with one magnet on the top face of the drill press pulley caused a terrible oscillating vibration.

I couldn't see spending $60+ on the MachTach units because it really is only a gadget to me and I could thing of a lot of other useful tooling I could spend that money on. I only thought to try these stupid things because at $15 I could add one to both the mill and vise and drill press. It's the gadgets that seem to always get me in trouble.

 

[GarageGuy]

Like Ray C, I just got a $30 HF optical tachometer with the reflector strips, and it works great. With my belt drive mill, I only have a few RPM choices anyway. It takes longer to change pulleys than it does to check the speed. Best of luck,

GG

 

[chip maker]

I have two of the MachTachs and they really work great to me. You kind of got what you paid for with the cheap tachs. After all the problems you have had with them you spent more time than they were worth to me. Just bite the bullet and give the MachTachs a try you won't be disapointed. I really think you will be very happy with the tachs plus you get to put them together yourself. I also beleave that if you contact Henry at MachTach he may be willing to build you one for an added cost if you don't want to build it yourself. Good luck. !!!