[ronncat]

I'm to the stage in my current Lathe CNC Conversion that I'm thinking about the electronics side. Can you give me your opinions on using optical or mechanical limit switches? Past experiences, pros and cons, and any other input is appreciated. Thanks

[Hans_G]

If you go optical, place and/or shield the sensor so chips cannot trip the switch. Chips get anywhere and everywhere eventually.

[Bubba]

I have both optical and mechanical on my mill/drill. Repeatability of both is well within the ability on my machine. As to pro/cons, it is easier to wire up the mechanical's and have them sealed up from contamination from swarf and coolant. Also, they have only two wires as opposed the the three on the optical. On my optical, I went that way as it is lever operated and the hysterious is much less than a mechanical. (this one is lever operated and the mechanical took to much space to work correctly)

I am now working on building a router to do PCB work and intend on trying some of the Hall Effect that I don't want to try on the mill as I mill ferrous metals quite often.

http://www.cnczone.com/forums/open_s...made_easy.html

art

[ronncat]

Art,
Thanks for the link!!! I have decided to try to use hall effect sensors for home sensors in my lathe conversion. I rarely turn or mill anything ferrous, so a weak magnet should not be a cause for concern. Also the magnets will be housed in (hopefully) swarf resistant enclosures. I'm also considering using these for spindle speed sensing to connect to Mach3. I've heard that proximity sensors may work better in that instance though.

[HoboCrow]

Hey Ron,

Check out the Sharp GP1A05 OPIC optointerrupter sensor for your spindle timing, it just needs a slotted disc.
Data sheet ...

GP1A05 Datasheet pdf - OPIC Photointerrupter with Connector - SHARP

I just put one on mine, but I had to modify the pinout placement a bit to get it in between the pulleys ...

Bill S

[ronncat]

Bill,

Checked out the datasheets. Seems like these sensors are somewhat similar to the optical limit sensors that came with my mill's Promica kit. Most of the info in the data is jibberish to me, but I can understand the basics. The tachulator on my lathe has an infrared sensor. It is currently configured to read 8 spaces per rev. I could redo this to have it read 1 space/rev which Mach3 can use, but then the tachulator is less accurate. I think there was a way in Mach to program multiple pulses/rev...need to look it up. I thought that by not messing with my tachulator and simply adding a second sensor, I could have the best of both worlds...easy for Mach and an accurate tach.

Ron

[HoboCrow]

Ron,

it's gibberish to me also ... ...

But, the positive aspect of this sensor is that as long as something blocks the beam (like a disc) it is OFF - No signal. When the slotted portion of the disc is present - light beam across the post (it's ON) - we have a signal. One slot = one signal per rev ...

Here's what I finally mounted. I modified the pinouts into leads and flipped the mount 180 deg from the pic below. Not a very good photo but you can see the single slot about to go between the sensor post...




It was originally mounted like this, but I couldn't position it properly on the disc.



Here is the top view showing the sensor post, disc (slot between the post) and the leads coming out of the sensor ... Works really well from a tested 20rpm and up to 915rpm (low speed pulley set).



Anyways, more food for thought ... :cheers:

Bill S

[ronncat]

Hi Bill,
Thanks for posting the pics. I had come to a similar idea in my thoughts last night. Anyhow, when I got up and was able to gather my bearings when looking at your super steroid enhanced spindle, I was pleased to say I was on the same wavelength as you.

I think that I will remove the spindle gear (the one that attaches to the power feed) since it has no use. I will turn an aluminum (Maybe iron) disc that will fit the spindle. Then I can either reduce the periphery and cut in a vane to use an optical sensor, or I can embed a magnet and use one of the spare hall sensors that I got for my home switches. I can then connect the Hall Sensor/Optical pickup sensor using a to be designed/fabricated mount that will bolt onto previously vacated holes in the frame of the lathe:wee:

Will investigate this further once I eat breakfast.

[ronncat]

Bill,

This is what I had in mind. Spent the morning playing with Shark FX. This is the first design that I have done. Still very rudimentary. I feel like a 16 year old with a driver's permit given the keys to an indy car....

Anyhow, here it is...don't laugh.

[Torsten]

I have both optical and mechanical on my mill/drill. Repeatability of both is well within the ability on my machine. As to pro/cons, it is easier to wire up the mechanical's and have them sealed up from contamination from swarf and coolant. Also, they have only two wires as opposed the the three on the optical. On my optical, I went that way as it is lever operated and the hysterious is much less than a mechanical. (this one is lever operated and the mechanical took to much space to work correctly)

I am now working on building a router to do PCB work and intend on trying some of the Hall Effect that I don't want to try on the mill as I mill ferrous metals quite often.

http://www.cnczone.com/forums/open_s...made_easy.html

art

Same results here, I tested out some optical switches and got them to work but ultimatly decided going with the mechanical one.
The opticals require more wires to route and are working only to pull down the current not the other way around.
The mechanicals I got can be wired Normaly open or Normaly close to suit a more flexible setup.
Simpler, easier, and more robust and still plenty of acuracy.

[Bubba]

torsten,
I lucked out in my junk box and found an optical and use it with a pullup resistor. This happens to be an axillary switch that I use for tool length compensation and have it wired in series with mechanical switches. Don't ask what the number is, cause its buried in the system and I can't read it. I was forutuate enough to be given some old copiers etc way back when and stripped them for parts. I had to use a test rig to find out which way round was closed circuit.
Just for your information.

art

[Isplat]

If you plan on running at slow speed. Having more than 1 notch for the tach sensor will improve the tach responsiveness in Mach3 and accuracy in tracking speed.

At 60 RPM the wheel only generates 1 event with 1 notch per second 1Hz update. This means it will likely take a couple seconds to update. With more notches, you will get more updates at slow speed thus improving tachometer performance.

Mach3 is configurable for this. I would guess EMC is too though I haven't used EMC.

-Ian

[HoboCrow]

Bill,

This is what I had in mind. Spent the morning playing with Shark FX. This is the first design that I have done. Still very rudimentary. I feel like a 16 year old with a driver's permit given the keys to an indy car....

Anyhow, here it is...don't laugh.

Ron,

I wouldn't laugh at you, maybe with you ... :stickpoke

You'd really laugh if I showed you my first solid model drawing ... LOL

I'm a bit grumpy this morning as I lost the ELS mainbrd yesterday during initial setup / testing under full power - Biggie, Biggie setback as it will have to go to Canada for repair/ replacement
The good news is that the designer is a Great guy and said it is under warranty - regardless!

fwiw: Before the smelly smoke, the opto sensor with one slot was tracking the spindle in the ELS with the same accuracy as the Tachulator using 8 black and white bars. Lag times also seemed the same ... that part was exciting.

Keep driving that indy car

Bill

[HoboCrow]

Bill,

This is what I had in mind. Spent the morning playing with Shark FX. This is the first design that I have done. Still very rudimentary. I feel like a 16 year old with a driver's permit given the keys to an indy car....

Anyhow, here it is...don't laugh.

I'm in a much improved mood today so I'll reply to this again ...

Looking Good! Have you imported the file into Dolphin - how did that look?

Bill S

[ronncat]

Hi Bill,

Glad to see that you got your problem resolved. It never occured to me to export the Shark file to Dolphin CAM...I merely redrew it in Dolphin CAD, and then opened the machining module.

Read on the Mach Forum that Dolphin had a deal on their turning module, so I took advantage of that. When I called Dolphin, I asked Rodney about importing from Shark as a solid. He told me that wireframes are importable, but solids not yet. The next version of Dolphin may be able to do that.

As you can imagine, most of that went right over my head as I haven't spent much time on Shark yet. However, just for fun, I exported that file as a dxf into Dolphin CAM...Looked kind of strange. Maybe it was just me, I'll have to delve further into it. Anyhow, as you know, the lathe conversion is mostly complete. Now I can spend time figuring out the electronic and software part of the conversion.

Ron

[Regnar]

You might want to take a look at proximity switches.

Inductive Proximity Sensors

Couple it with these relays and you can wire right into the breakout board.

PIR6W-1P-12VDC


I want to say they make water proof wire connectors for them so coolant will not be an issue.

[headsmess]

stupid frying pans. stupid fires... chips and swarth..accuracy...repetition...cost...arrrrgh!

currently im cheating and using nothing.

anyways. me and me mate, having a fiddle with these lil interruptors.

i decided it would be best to use a continous strip, as wide as the op's gap... self clearing. with just a slot for the actual switches.

meh, thats neither here nore there.

what we did end up with was a simple circuit, with a 2 LED display.

green was a-ok, red was limit nearing, as a visual indicator, then we could adjust(selecting resistors) the distance between the red indicator and the actual limit itself.

still making a lil pcb up for them, etc...but if anyone wants the schamatic....

[Bubba]

Sure would like to see that schematic! I'm in the process of building a new machine and looking at all alternatives.

Look forward to seeing it.