Limit Switch Sensor
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- เผยแพร่เมื่อ 21 ก.ค. 2022
- In this episode I am testing several different Limit Switch Sensors to improve the accuracy of my CNC Router. I choose 5 different Limit Switches that I thought are a popular choice and that made sense to me. You will note that there is no capacitive sensor, this is because they usually have too much fluctuations with environmental changes. Most of the Limit Sensors are accurate to 0.015mm and it was a surprize to me that the cheap simple snap action switch was this accurate. On the contrary the hall sensor I was disappointed by. I don't mention this in the video but a possibility is that they are rated to run on 6-24V and I used 5V as they seem to function fine. I think that the accuracy was possibly lowered by this. The Metrol switch is the best and just blows away any other option.
Check my site for more information:
www.JBWorxstudio.com - วิทยาศาสตร์และเทคโนโลยี
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Thanks for your video! Ive had several repeatability issues on my Z axis (even without a tool change or tool re-measuring) after it homed Z using inductive sensors ranging from 0.02 to 0.2mm. I think I'll also go for the Panasonic
I think they are great for the money and one big advantage is that they run on 5V. Many controllers have a open collector input and require 5V not 12 or 24 volts.
Intetesting test! I've opted for inductive switches, cheap chinese ones for a couple of euros. Repeatability is also around 0.015mm, enough for my needs. The thing you need to be careful about with these is temperature drift. If you work on a piece for many days and you use it in an unheated space and the temperature changes 20 degrees c, it may be off by 0.1mm. for woodworking it isn't much of an issue but for metal it can be a problem.
Well there are definitely quality differences. The hall sensor should have performed better but it was a cheap one. Also in general it does matter what voltage you operate them at. The lower limit can cause some issues. Quality sensors usually contain a good amplifier and are temperature compensated. Thanks for your comment!
@@JBWorx True, especially hall sensors since these work with very low signals, and cncs are rather noisy in electromagnetic and supply voltage sense. Some shielding of the sensor and shielded cabling and a good quality psu might help. Still a mechanical switch is not sensitive to these kind of things and inductive sensors may be better suited to cnc environments. Optical is only practical if you can keep dust out of the signal path with compressed air or by encapsulation.
I've held some ferroes metal chips against an inductive sensor and it didn't trigger, only a more massive piece of metal can change the oscillation frequency enough for it to trigger. I've had trouble with microswitches, either chips preventing it from triggering or working it's way into the sleeving and shorting out contacts or being destroyed due to the cnc running into it at full speed not being able to come to a complete standstill in time. With contactless sensors it's possible the axes bump into something solid before destroying the sensors.
Yes, I share your opinion on shielded wire. It is very important, I have seen so many DIY machines riddled by problems that in the end were noise related. Cat5 wire works great and is cheap to use for switches / sensors unless you buy the more expensive shielded version like the Keyence but they are around $100 a pop. The way the sensors are located on my machine I can give the optical sensor a shot. And they are easily accessible and can be checked easy as well. I have a plan for the Metrol switch, I am building a tool length sensor and I think it will be perfect for that. But yes you are right the optical sensor is about 10 fold more fragile than the good old prox switch in a stainless steel housing. But however also 10x more accurate.
Great test - and content in general - but quick question and excuse me for not having the lingo correct. But does EdingCNC set the home point of the On signal of the switch or does it "wait" until the Off point? Reason I am asking is that supposedly the repeatabilty of the Off point is not always as good on some switches as the On point?
Eding sets it on the “off” Point. So all switches have a hysteresis. This means there is a difference between the “on” and “off” trigger point they are not equal. However the repeatability in either direction is often more dependent on speed and temperature.
Nice video. Your presentation style is very good and clear. Good work.
Thank you Nick. Comments like this make it all worth it.
@@JBWorx I get it! I just re-edited a bunch of my videos to remove dead air space. I got bored listening to myself, ha ha. You have a natural listening experience on your videos.
Thank you! Yes there is a bit of a learning curve and most times I explain with way too much detail and end up editing 50% of it out. It gets too long and boring. It’s a bit of a balance.
Thank you!
Got one question
So in industrial machines that use, like you said, clunky switch online have a servo driving y axis, is that right?
If so, dual motors y axis machines would need the same homeswitches system that your machine have?
Not quite. The servo motor is better and the software of the motor offers an output called “Zero Pulse”. So once the clunky home switch is made the machine will now look for the zero pulse of the servo and that is very accurate. Thank you for your question.
Klasse Video, wirklich interessant. Das mit dem Micro Schalter hätte ich nie geglaubt;) weiter so!
Danke Thomas!!
I had upgraded to the metrol precision switches a couple of years ago. They have worked well. Any issues with optical sensors and chips flying through them and flagging a false positive?
No not at all. They are only active at the moment of homing so no machining at that time, but I have not had a single incident with any dirt, but then I also clean my machine a lot.
The optical sensor, being housed in plastic, will likely accumulate electrostatic dust that would eventually disrupt its sensing ability. Garage door safety sensors are notorious for incurring this issue. Always trade-offs on which solution optimizes the pros while minimizing the undesired cons.
I have these installed now for 9 month and can attest that I had to never clean them. Not from any dust and also not even from plastic chips that like to kling to everything. In hind side I should have installed these years ago.
@JBWorxStudio thankyou for the great video's you post. Which Panasonic sensor did you go for? Or it doesn't matter? Thanks again.
It really does not matter, they are all the same in that family but the form factor is different. So the mounting on one axis might be different than on the other and you can choose the one that mounts the easiest. I am still rather happy with them and really can recommend that change.
Ok, thanks, which family is the one you tested from? Am ready to buy now, machine getting close to working 🤞
Look at the Panasonic PM25 also note you can get them with 1m or 3m wire length and make sure you order what your board needs so either NPN or PNP.
@@JBWorx awesome thankyou
So awesome that you get you machine going.
I'm looking at some button style switches for homing and limit. How do they compare in accuracy to the little Omron switch? The switch I'm looking at is PBS-110-x6C, by Twidec.
The mechanics of a push button switch are different than a snap action switch. So I don’t know how these will compare but I really would go with a snap action switch the repeatability will be better.
@@JBWorx Ok, thanks.
👍
the best would be a combination inaccurate home switch + encoder wheel index from your motor. I read somewhere that HAAS CNC machines do that.
Yes most servos can do that as they have what is called a “zero pulse” it comes up once every revolution. The home position is set very accurate this way unfortunately the hobby steppers and servos miss that feature.
I have a question, say you homed the cnc, then you setup an offset to be the 0.0 of a piece...
And lets say something happened you had to stop the machining and lost that 0.0, if I home again, and set the same offset, will everything be allright?
Yes, it will be!!! That is one of the advantages of having accurate home switches. I am scripting a future video that explains how to use G55, G56 etc and never zero out a tool again for X and Y. This also goes hand in hand with the mounting plate I use on my machine so you can set parts and fixtures (like a vice) back to the same position every time. Hope my explanation makes sense, if not then make sure to watch the upcoming video on that topic!
@JBWorxStudio
Klasse Video! Du bist einer meiner liebsten TH-camr was DIY CNC angeht. Jedes Video ist voller hilfreicher Informationen und nicht nur Entertainment. Das ist finde ich super! Weiter so mit dem tollen Content! Ich habe noch eine Frage zu dem Omron Taster: wie lautet die Hersteller Teilnr. ? Bei Mouser gibt es so viele Varianten ^^
Danke! :)
John vielen Dank für dein Feedback das motiviert ungemein!! Hab mir gerade den Schalter angeschaut und der ist total voll mit Klebstoff … aber auf meiner Webseite ist ein Bild. V-165-1C5 der hat eine Schaltrolle die ich aber gleich abgeknippst habe.
Das freut mich! :)
Ich bin noch sehr neu in diesem Hobby und habe weder eine Ausbildung noch ein Studium absolviert dass mit dieser Materie zu tun hat. Dementsprechend sind diese Videos eine wirklich klasse Informationsquelle!
Danke für deine schnelle Antwort!
Viele Grüße :)
Viel Spaß noch mit dem neuen Hobby
I bought some of the Panasonic NPN PM-U25's, is the black wire(connected to +) for NC? or the white wire? The terminology of the manual says Light On/Dark On for each of the control wires?
Light On means the output is high with nothing in the beam. Dark On means if the beam is interrupted the signal goes to high. So for NC you would want Light On. Hope this helps
@@JBWorx perfect thanks
👍
La switch omron que tu a utilise c'est quoi son numero de piece ? sur quel voltage elle fonctionnait ? merci
I made a nice project description on my website please see the picture of the switch there. Voltage is 5V.
www.jbworxstudio.com/switches
I'm converting a small benchtop milling machine to CNC and I'm wondering about microswitches.
My need is to have cheap and repeatable ones with a good resistance to dirt.
I'm thinking about making an enclosure for moped ignition points, moved by a spring loaded plunger.
They're durable, precise and cheap...
What do you think about this possibility?
It’s an interesting idea but they are not really good if there is any dirt. Also I think that the snap action switch ($5) will be a better option. The “snap” is that provides the repeatability. But hey make a test it’s not much money as you said. Maybe you will be happy with it.
@@JBWorx yes, I want to test them, because I want something tough.
I think that making an enclosure with a protruding plunger, with seals to make it waterproof, is more than enough, and the mechanic of the points, precise and repeatable in an environment in which they are opening and closing faster and precisely for long periods of time, is a warranty for precision.
Maybe I'm wrong and I'm going wasting time and money...🤣😉
Only one way to find out. Please share your findings.
Great video
Thank you appreciate the feedback!!
Great to see some testing done and good to know that most are accurate enough for us diyers. Just wondering if you have a graph of the results or could post the raw data somewhere for us? Thanks
The data is a bit unorganized but all complete at the moment. I am trying to write a project article on home switches and upload that to my website. I am still learning on how all that works and I tell you it’s not easy. I spend a good 3h this afternoon to add a single project page just to hit “undo” in the end. Lol 😂 so yes please check back on my site www.JBWorxStudio.com it will be there soon … I hope 🤞
It would be grat to have the exact typ of those tested models… (specially of the better ones) thank for this great explanation of all typ of switches, helps a lot!
Thank you Murat, you can check my website for more information. www.jbworxstudio.com
@@JBWorxcan you please tell me which model the omron is? I couldn’t find this information on your website. Thank you!
There is a picture of the switch. However it is V-165-1C5 I took the roller off but left the metal strip in place.
Are you able to share the part number of the Panasonic optical sensor? I understand if you want to keep it proprietary since you did the research to find it.
Not a Problem I share it … matter of fact it’s in the comments here somewhere. So look for the PM-24 series of optical switch there are a lot of different versions all with different mounting options the sensor is the same. Make sure you order NPN or PNP according to your board. I find DigiKey the right place to look them up. PM-k24 or L24 work in most cases. Hope that helps.
@@JBWorx Thank you very much!
😀👌
One more question:
- The Panasonic optical 4-wire switches, you only need two of them depending on whether you run then NC or NO?
(I am about to order switches and signal wire online;))
[edit] seems like it's a tad more involved. The data sheet seems to say you'd need some resistors, too. Well, I still am not sure how many wires you actually need in your signal cable. Maybe all four? Two for power, two for signal?
So the NO vs NC has nothing to do with how many switches you need. Most bang for your bug is to have one homing switch per axis and let the software take care of the travel limits. The Panasonic optical sensor has a logic output. So it will be zero volt or Vcc let’s say 5V. This means you will not need a pull up or pull down resistor it should work without one. Also you have the option to use the NO or NC wire as the connection for to your board. So this means you need a 3 wire connection. +, - this will power the switch and one signal wire. I hope my explanation makes sense.
@@JBWorxsorry, I wasn’t clear. I didn’t mean “how many switches”. I meant how many wires would it need, but you answered that:-). Thanks as always!
I’m ordering parts these days so the build will commence when all is in;-)
Excellent ! I think you will enjoy these switches easy to install and wire and I really like that they run on 5V with a very low current draw so you can connect them directly to you control board. Good luck on your built
Some questions....
Are limit switch also a homing switch too? Since arduino cnc shield don't have pins for homing it has only limit switch pins and if it's separate switch, how many it needed or just homing switch installed on z axises and it also installed both sides? Like z+ z-?
Hmmm I am thinking how to best answer that- In your case they are the same. The switch will be the homing switch. No there is no switch for the (-) direction necessary so only one per axis.
can you tell us what the part # is for the Panasonic optical slot sensor? Thank you.
There are about 10 variations depending how the switch is fastened down … so hole location. You can find them on Digikey.com look for PM-L25. You can also read up on my website www.JBWorxstudio.com
Thank you very much.@@JBWorx
Glad to help
Good info
👍
Maybe there are a better solution ....AS5600 magnetic encoder 12 Bit encoder.. pcb module is 1.6 USD and ATTINY85 3 USD on Ebay..
if better resolution is needed AS5047 14 Bit. feed the inductive signal and rotonery encoder signat to the ATtiny85, and program an output. what do you think?
Definitely a cheaper solution. What I liked about the DRO is that it was ready to go out of the box (minus the calibration). If you try your solution out plz let me know how it went.
Could you please post the name of the awesome Japanese switch ?
Highly unlikely I would buy it, just want to learn more about it.
Yes certainly
The company is called Metrol
The switch is PT5M1CB.
You can find them at
Automationdirect
Misumi
And sure enough Amazon
Wow over $200 each! Guess you’re paying for accuracy
I think I payed $100 for the 1micron switch
I suppose you could build a test stand of superior accuracy to do automated quality testing on the snap switches. Buy a quantity of them and "certify" the highest accuracy, lowest variance for use or resale. Or produce matched pairs for dual stepper axis or other use. Probably not worth the effort mostly but an interesting exercise.
Actually that is a really good idea to make some $$ that has never occurred to me. Thank you for pointing it out!
You never said how much the little micro switch that's made in Japan and use them Toyotas assembly line cost?
There are different plunger versions available and the cost is around $100.
Did you ask for wireless way to use cnc probe? I think i found a way to get results in range of microsecond with esp32. I tested that long ago and results where not satisfying as it took 5ms but how with some functions from edf you can establish much faster connection with esp-now. And my tests show that latency of pavket may be as low as 1us.
Yes exactly I had the ESP-Now protocol In mind. Would love to get some more information on your work. !!
@@JBWorx there is also a faster way with raw data. As probe is one way important information it could be sent in broadcast mode and reciver could just listen raw packets. That would speed up as there is no confirmation pavket to be sent.
But I think this may be sufficient as if I remember correctly old renishaw probes used infra Red and that was about 50us if I remember correctly. So 1-2 microseconds would outperform it.
@@JBWorx its so simple get two esp32 and arduino example for esp-now. Make it send byte in a loop and make byte value be state of probe pin. You have to install also IDF framework that works with vscode. Thrn you can include headers from IDF into your arduino sketch. There is just one line of code beside header that you have to add to make connection faster then default. I can show you.
The listening mode makes perfect sense now were you explain it. I think I would be happy with 15us moving slow for sending you can always make a second slower move and the error would be really small
That sounds really good. I have 2 esp32 and an arduino !! But I will be on vacation till March 6. Traveling. I would love to work with you on this project. !
Optical is great, but be sure to shade it from direct sun or room lights. They can destroy the accuracy.
Hmm I cannot really confirm that because I assure you when I film a video on my Maschine there are 5-6 lights involved.
@@JBWorx It isn't the presence of light that is the problem, but changes in ambient light level. Compare lights on to lights off to see if there is an issue for you.
Ok I will take note of that and see if there are any changes. However these have a built in amplifier and also a clear high or low state so there should really be no difference this is why I choose the Panasonic one.
Maybe try to make a spring loaded lever on a pivot point to increase the accuracy of the cheap switches by the lever ratio?
I think a direct travel into the switch will be the most accurate solution, make that point of contact spring loaded is actually a really good idea I never thought about that. For the cost I think the optical switch is a really good solution. I run them since this video was released and I am really happy with them. Thank you for reaching out.
Nice one, what if I told u that u really dont need any of these to maintain your square, i use one driver to drive both motors and they never off sync and that is for many years so far
I use integrated servo motors so the drive is part of the motor. I use the software to set the axis to square but you can totally do that mechanically as well.
Those inductive switches get really bad when the temperature swings.
The little micro switches.... The accuracy depends on part on which portion of the lever arm you are engaging. Between the fixed point and the button is much more accurate than at the end of the lever arm, furthest away from the fixed point.
Yes, you are correct. There are some temperature compensated sensors usually around the 100$ mark. I tried to set the micro switch with a steeper angle towards the moving part so mechanically the guide block seen in the video would not be able to pass the switch, something would have to break. So that is not quite how you want to do it but like you said provides the advantage of a better “contact angle” for the switch. Anyways I am really happy with the optical sensors the past 3 month or so.
I guess its a moot point if you zero from your work or vice using an edge finder for example.
For the WCS yes however my machine das a dual driven y axis and if the homing is of so is the 90 degree X to Y.
Please, is there a list of model numbers or where we can find the switches you mention? Great video and loving the series, Many thanks.
You can check my website
www.jbworxstudio.com/switches
Also google Panasonic optical slot sensor there are a lot of different versions but they are just changing how they mount, NPN or PNP and the wire length.
Salut j'ai posé 1 capteur par axe . Posé à 90 degrés des tiens il sont au milieu de l'axe les butées métalliques à droite et à gauche
Avantage tu économise des entrées sur la carte et si tu vas trop vite en fin de course tu ne risque pas d'écrasé Ton capteur
Si tu as des infos sur un Gcode pour palper une pièce rectangulaire je suis preneur merci pour tes videos
One sensor per axis is usually sufficient. The controller usually has software limits and will apply these from the sensor position. Best is to mount the sensor so that the switch flag can trigger the switch but nothing will crush the switch if the axis would drive further to a hart stop. Good that you have added these to your machine it’s defiantly an upgrade.