Question about Hall switches that I am planning to use as limit switches.

@zander There are woodturning clubs in Canada and I know people who have demonstrated up there, so it is doable. I don't have a clue as to how they're doing it though.

@pritchs That helps a lot. Since you are not a newbie then doing the programming for this isn't a huge challenge and you understand the environment. I don't understand how you are legally allowed to bring a lathe into any public space, the risk of injury although remote is non-zero and we know how risk averse those organizations are. Something does not make sense now.

@pritchs Just make sure you don't allow alum touching alum, it will grab, use uhmw blocks between.

@pritchs I used to work at Lee Valley. We had to stop doing demonstrations due to insurance reasons. We almost had to shut down our fly tying club over Directors Liability insurance but was able to get umbrella coverage from the church we met at. Super expensive for a club of less than 10 most on fixed incomes and I don't mean corporate pensions. Food bank members many were.

@will Yes, we do have a Lexan shield. That is mostly to protect the audience. I have never seen a club setup that set up anything to protect the camera. Playing the odds I guess.

That said, the camera is seldom exactly on the path that an object would follow. it is usually slightly toward the tail end of the lathe and pointed slightly toward the headstock. So, any object coming off the lathe following a path 90 degrees from the center of rotation should miss the camera. Should....

@pritchs The last time I was at a woodshow, the ticket you bought had a legal contract on back re liability. Also any dangerous demos had lexan shields between demonstrator and public.

@zander The point of having the camera where it is, is to give the audience a view that is zoomed in close enough so that they can see the details of what the demonstrator is doing. A wide angle is better than nothing but is essentially useless to the audience. 

The camera weighs slightly under half a pound.

Yes, I am in the US.

I think that's all the things I missed! 😀

@pritchs To get back to your original query, you have the technical background to do a few google searches to determine how to use the HALL effect switches. I don't think it has to be an interrupt thing, just check it for either open or close depending on how you hook it up in the main loop, this isn't rocket science. You could also use magnetic reed switchws, the version I use has both NC and NO terminals. Also a simple micro switch like any shown in pic will also work. Good luck.

A big thanks to everyone that joined in this discussion!! It's been fun and you have helped a lot. 

I wondered if I would get any response at all when I posted the question. Thank you all!

SP

@pritchs Do you have remote zoom?

Hi @pritchs, Again..the solution to your problem is simplicity.. the Diffused photosensor is probably the most reliable as I have over 40 years experience with an array of sensor technology in the industrial sector. How ever, which ever sensor you decide to use, the code can be written to be a failsafe..in the absence of a high signal.. the motor stops! This takes care of loss of power to the sensor, and since the hall effect is so inexpensive, you can get 20 of them for about $8 or $9 US, https://www.amazon.com/Hall-Effect-Sensors/b?node=306929011

Aside from shorting them out, or losing power to them..they're reasonably reliable. mechanical limit switches, like micro-switches as ok, but can easily get out of adjustment or alignment, contacts can corrode if not hermetically sealed, are much larger that a  Micro-switch , the Hall are TO-92 style case ...

While I agree with your farm analogue of trying to prevent bad things from happening, using two in parallel with proper current limiting should do the trick..

Best of luck on your most interesting project..

Regards,

LouisR

@zander It's much the same in the US. We have an international woodturners organization and they require shields at all of their sponsored events and highly recommend that their chapter clubs do also. I belong to three clubs and all of them require one also. Ignoring all the legal issues, it's just common courtesy to your audience to make sure they aren't injured.

Thanks for the post regarding the switches. I tend to run down all sorts of rabbit trails before I settle on the way I want to do something. Hall switches and interrupts are possibly good examples. 😀 

Thanks for your suggestions.

Cheers,

Steve P

@pritchs Interrupts are a bit dicey, the documentation is not easy to find, and there are special macros that are needed. You don't really need interrupts, just read the pin.

@zander Not built into the camera, but I have a solution for that too thanks to YouTube. 😀 😀 😀 

It is basically a metal bracket that fits around the bottom and side of the camera and holds a servo motor. Hot glue/epoxy a small 3D printed "wart" onto the zoom button on top of the camera and connect the two with a stiff wire shaft. It's a little more complicated than that, but not much. I already have that working since I THOUGHT it would be the most difficult part. Better to fail early and quit was my thought. That went fairly smoothly. Then I got off into limit switches..... 🙂

sp

@inst-tech Thanks for the info. It helps a lot to get advice from people like you and others here that have been in a particular specialty and have real-life experience.

From this discussion, I'm going to try photosensors. They seem to be the least trouble. But then again, that's why I went the Hall switch route. 😀 The limit switches are the last major hurdle I know about, so it ought to go relatively quickly from this point. But who hasn't thought THAT before? 

Thanks again.

SP