Thread: Mars Lathe DC motor conversion.

Hi Stuart,

I just got my induction sensor too. What makes you think it's only good to 27Hz? Did you get specs with yours? The basic wiring diagram at the base of my actual sensor is ALL in Chinese, I had to guess which is +, GND and output! It works OK though, even on aluminium, I don't know why but I had it in my head that it only works with magnetic materials but I think that is for Hall effect sensor, I got that many sensors now that I confusing myself!

If my induction sensor is only good to 27Hz then that's my plan up in smoke too! Well, once I get past 1600 rpm anyway! 27Hz, that's crap, who makes a sensor rated to only 27Hz?!!!! No wonder they are cheap.

The 1 on 1 off or 1 on 5.75 off I would thought would not be an issue since I'm assuming it's edge triggered?

Simon

Product Name	Inductive Proximity Switch
Model	LJ12A3-2-Z/BX
Theory	Inductive Sensor
Wire Type	3 Wire Type (Black, Brown, Blue)
Switch Appearance Type	Cylinder Type, Metal Shell
Output Type	NPN NO(Normal Open)
Diameter of Column Sensor	12mm
Detecting Distance	7mm
Supply Voltage	DC 6-36V
Current Output	300mA
Response Frequency	0.5kHz
Detect Object	Iron
Total Size	6.6 x 2cm/2.6'' x 0.8'' (L*W)
Cable Length	1.1m/43.3''
External Material	Plastic, Metal
Net Weight	42g
Color	Silver Tone, Orange, Gray
Package Content	1 x Inductive Proximity Switch

According to this mine is OK to 500Hz. Ah! "Detect Object: Iron" That's where I got it from, thought it was the voices in my head!

Soon find out!

Simon

Hi Simon,
I bought one like that and another that looks just the same with only 4mm detecting distance and no Hz spec. Not sure which on turned up, I'll try and work it out.
I might have confused you. I think it only works at 27Hz because of my setup. It works ok at slow speeds but at about 800rpm it stops triggering. I am guessing this is because the dog isnt "there" long enough. Time wise my math says if I went to a single trigger point that covered 180 degrees it would run at 182Hz. So still a little on the low side but the dogs arent the perfect shape and have a slightly different distance from the sensor.

What are you planning to use to trigger yours?

Stuart

Hi Stuart,

OK I'm with you now. Originally I was going to make a setup inside the mill head but installing a sensor immersed in oil and routing the cable outside seemed unnecessarily complex. I'm going to mount a pickup on the base of the quill shaft underneath. I plan on making a clamp on disk (about 10mm thick) with two pickup nodes. This will clamp on the quill shaft.

I should have this made and installed on Tuesday (working saturday & Sunday ). I'll post some pics when I get it done.

Cheers,

Simon

Here's a few pictures of tacho setup on my mill, it has worked very well so far.

I drilled, spotfaced and tapped a hole through the side of the vertical head to allow the inductive sensor to pick up directly on the slots in the bearing locknut.


The sensor has an LED potted into the end next to the cable to indicate that it is registering a signal.


The particular sensor needs to be 1mm away from the rotating surface, this distance is rather critical with this type of sensor but is easily adjusted with a screw in type.

Techo, we have rules here you know.
Posting pictures like that in a thread about lathes is not on.
Please find the "Show us your mill thread" and post more pics about that mill!

Michael

My guess is that its a K&T....puts some pics and info in show us your mill Please!

The only "Show Us Your Mill" thread I could find was related to portable timber mills, is there another?

Lex.

https://www.woodworkforums.com/f65/sh...r-mill-121568/

Stuart

Well I don't know what I've done.
First time I hooked the Hall sensor up I paralleled it with an inductive sensor by mistake.
Both leds on the Hall sensor are on , magnet switches the sensor led off. Tacho worked but only at slow speed.
Rewired without the inductive sensor, now just the power light comes on and I cant get the magnet to switch.
If I disconnect AO from the yellow wire on the tacho, the sensor will then switch but thats not a lot of use lol. Still only at very slow speeds.

The speed maybe fixed with a bigger magnet and a more carefully adjusted sensor.

Have I toasted something?

Any ideas?


Getting close to going back to doing the maths in my head

Stuart

Hi Stuart,

You're a smarter man than me so if you can't figure it out, what hope have I got? LOL!

Both my hall switch and induction sensor have an LED in their rear but it only comes on when they detect. My sensors have a Black, Brown and a Blue wire. Their choice of wire colours confuses me but with mine Black is GND (no surprises) Brown is +Vcc and blue is the output signal. I have incorrectly wired BOTH sensors (I powered up their outputs by mistake as I thought the blue wire was +Vcc) and after I figured out my mistake I rewired them and they still work fine. According to the literature, my sensors (yours probably the same) can source 300mA which is a fair amount for a sensor, so they must be fairly robust.

Tomorrow I have been promised 1/2 day in the shed so I plan on tapping the grub screws on my sensor pickup for my mill, I'll do some peed tests to see how responsive the sensor is. I have yet to test my sensors in real situations, only waved the target material near them to check that they go on and off. I may find too that the speed of the signal may get beyond the frequency response of the sensor and that the 500Hz spec is a load of crap! I would expect that an erratic result will occur as it approaches it's limitations.

I'll report back.

Simon

Originally Posted by simonl

I'll do some peed tests to see how responsive the sensor is.

Hmmm...sound interesting.....

Hi Stuart,
Not sure on the sensors you are using, do you have an oscilloscope so you can see what is going on?
Did you want me to put a couple of the HE sensors i am using in the post? They just need a pull up resistor and i have tested them to over 4k. No flashing lights and you will have to mount them on a small PCB and i suggest dipping them in epoxy but they do work!

Hi Simon,
Not so sure about that.

"Both my hall switch and induction sensor" you mean a Capacitive and Inductance Sensor? (both mine have LEDS but I am talking about one of these.
Hall Sensor Module M44 Switch for Magnetic Field Detecting 16mA DC 0-15V | eBay

You'll know when you hit the limit, the rpm starts to drop as it misses pulses(of course yours may work just fine with your encoding ring(I think thats the correct name?). If not you can always make a new one with 90derees segments.

Hi Ewan,

I'm using the same sensor and tacho as Rob used here
https://www.woodworkforums.com/f65/ma...ml#post1565977

Thought the tacho is a 12-24V one
0.56" DIGITAL Red LED Frequency and Tachometer Rotate Speed Meter DC 12-24V | eBay

No scope.... though I have been looking at them for the last few months but I hadn't convicted myself I need one.

Pull up resistor. do I need one of them? I read about them in another post. maybe I should reread this thread properly rather than flipping through it.

I'll play with this one a little longer.... its likely me doing something stupid....... If I cant get it going I'll gladly take you up on your offer. I had planned on removing the sensor from the board anyway.

Stuart

Hi Stuart, my mistake about the sensor!

Hey, I think we may be in the same boat now. Do you remember me saying that I found the wiring colours a little confusing? Well I think I may have let the magic smoke out of the sensor! After connecting it up and seeing it do nothing, I had a look at an email from the seller after I asked them about wiring. Turns out it's: Brown +Vcc, Blue Gnd and Black is signal. It had been a while since I played with it and forgot that I forgot which wire goes where!

Anyway, to cut a long story short, I wired it up incorrectly and now I can't get it to work. The LED at the rear indicates a signal but the output is fixed at +Vcc. Ahhhhhhh!

I'm about to order another one, not that the $6 worries me, it's the painful 3 week wait!

Stuart, I hope you have beeter luck than me.

BTW, with the LED tacho, the instructions are confusing. S1 is the switch on the LHS (looking at the back with the cover off) and S2 is on the RHS? I have worked out how to select between freq and tacho, I assume you use slection "3" unfiltered? I think I have also managed to select the divider (3 for my situation) but how do you change the decimal point and it's resolution?

Had a look back over the "Wow huge Price Difference" thread but could not find anything.

Cheers,

Simon