#211
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Brian,
4 proxies total. 2 on the gantry 1 on the y car 1 on the z 2 on the gantry (can be used for autosquaring) but more importantly for bilateral detection of a derail. |
#212
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Makes total sense. Thanks Sean.
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#213
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Reed switches
I was thinking of using reed switches as limit switches just found a post that says, not a good idea.
will go with micros switches what type micro switches are best and where can i locate them . will be importing them from the usa. thanks woodguy Last edited by paul60; Thu 15 October 2009 at 06:09.. |
#214
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Microswitches, the roller kind? I have those on my machine now and have used them in the past and I do not like them. They are for the most part cheap and outdated technology and as I have read here there has been great success with the inductive proximity sensors listed in this very thread. You will pay more up front but they are better for our application.
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#215
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Please advise me on this one:
1.st : I understood that E-Stops have to be set up with two contactors each, first one interupting general electricity and the other one giving a contact to the BOB (PMDX 122) activating the charge pump. Please just confirm if I can leave it like this. 2.nd : If Proximity sensors are all setup in series thru relais giving signal to one input Pin 15. According to Seanīs Layout. How is then the homing functioning? Should not each sensor and relay have itīs own input signal? Or giving the two sensors on the gantry each one input, and one common input for the Y Car and the Z? So I could use 3 inputs for proxies and one remains left for the Probe? I saw that the new PMDX 125 has alot more inputs to choose from, but as I use 122 it seems that lining up in series all proxies u never know which one gave the signal and homing is not functional!? Thanks for advise. Claus |
#216
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Hi Claus,
I'm also looking for a solution to your Q1. Q2. In a ideal world + common logic, every switch should have their own input port but each D-25 pin parallel port can only have 8 bi-directional (in/out), 5 in, 4 out. Then you don't have any more port for your touchoff probe or other input of your choice. You can have more if you daisy wheel a second BOB & use a second Parallel port, then you can do whatever your heart desire. Its a compromise. As long as you "tell" Mech3 & EMC2 you are sharing ports, & follow a predetermined protocol, the software are clever enough to tell which switch activated the input port. Its the electronics + software thingy, they defy common sense & they do work. But now the bigger question is how many switch, which type & what position to choose that is bothering me... Again, you may worry the software will screw up, but hey, what else won't? I hope this is helpful & not misleading |
#217
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Claus (and Ken):
Many (most?) contactors have one or more "auxiliary contacts" - and are often expandable with more. So you can potentially use an auxilliary contact on the contactor that interrupts the main power to inform the BOB of the status of the contactor. On your second question, the software only moves one motor at a time during the critical parts of the homing process, so it knows which limit is being hit. Note that in the early phases of the homing process, it can move all of the motors at once, until the first limit is hit. Then it has to back off to figure out which limit triggered. |
#218
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I think we are getting confused with word choices:
A "contactor" is similar to a relay. It contains pairs of "contacts" for opening and closing circuits. The E-stop pushbutton switch also has one or two pairs of "contacts". Claus, in your Q1, I believe that you meant two "pairs of contacts" instead of two "contactors"? |
#219
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Gerald, you are right. Sorry for my english. I meant two pairs of contacts. On the E-Stop switch I use can be mount 3 pairs in a first row.
One pair of contacts will interrupt general electricity in the control box and the other pair of contacts give signal (contact) to BOB. Right? For the sec. question to give you some background about my Constellation: PMDX 122, Mach 3, 4 pcs ProxSensor NPNand 4pcs. Relay like the one in the pic. RELPOL.jpg The reason I am badly confused about homing is because I`v never seen it work in reality, I don`t know the sequences and how it is done by the software. I`m totally lost. Ken said I have 5 inputs and 4 outputs, should I use them like this? Variant A 1. Input Gantry far 2. Input Gantry near 3. Input Y and Z chained 4. Input Probe 5. Input ? Variant B (Brad, does it mean homing is done by software Mach3 and recognizes by itself?) 1 Input this classic scheme 2 Input Probe. Which of the Variants is mostly used make homing procedure available? Shame on me.... Thanks Last edited by Claudiu; Mon 14 December 2009 at 10:07.. |
#220
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Right.
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#221
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Claus, look here: http://www.mechmate.com/forums/showthread.php?t=605 for some discussion of how homing works when the switches are wired as per the scheme (schematic) you noted above.
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#222
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Hey Sean. can you tell me why they are wired in sires and not to separate inputs? I can't see how this would work for homing...
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#223
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John,
Let's see if I can explain. Mach is funny, that it actually has a built-in homing macro for finding home. It is designed to step through it's seek-n-find sequence going x, then x1, then y, then y 2, then z. Depending on the number of motors you have and such, it will configure the routine to home accordingly. If you have and x1 and x2 motor, then the auto squaring feature will be active. If you choose to use this feature, be prepared to make the eccentric holes in the rail adjustable to fine tune the "perfect square" of the machine. .... back to explaining. Since Mach already does this homing routine, you can wire the contacts in series to one input on the BOB. The downfall to this "series relay logic" is for some reason any of the axis' that is active is triggered by a limit/prox switch not on that axis, the machine will be improperly homed and usually ends up derailing the machine. The only time this happened is when I physically triggered a prox sensor on an "alternate" axis during the routine to see what would happen. Good thing my estops work! The mach3/artsoft manual explains the routine in detail. Does this answer your request? Sorry for the delay - I have been out on vacation for a while. refer to my post WAY back in time for the wiring part of this reply. Sean Further autosquaring discussion moved here Last edited by smreish; Mon 04 January 2010 at 20:54.. |
#224
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Thanks for your reply Sean. hope the the vacation time was good...
The delay did give me time to reflect. I have a machine running Mach in Jacksonville with micro switches. So I am familiar with the workings of Mach 3. I guess the question comes from the PDF diagram showing all switches open. So if my thoughts are correct then during normal state (proxies not over a hole) would keep all circuits closed. And when the homing routine is active each axis will in turn move over the home hole and back off re-closing each relay in turn. I am sure this has been covered before, and don't want to add any confusion but rather contribute clarity. |
#225
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John
Clarity understood. Yes, the proximities are always in a "hold the switch" closed when active and any incident that causes release will fault the machine. Similar in logic to an estop switch circuit where every switch in the circuit is required to work and be active for the entire system to work. Helpful when you attempt to derail the machine. Hope this helps. Sean |
#226
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Just a new idea: Safety "switch" by using only the V-wheels and rails.
I had a crazy idea and would like to throw it out there.
Imagine if we could electrically isolate each V-Wheel from the gantry. Imagine if we put a wire on the wheel (on it's holding screw) and also a wire on the rail that the wheel rolls on. Wheel on rail = closed circuit wheel off rail = open circuit Would it be ok to wire this circuit to a break out board? I know that probably most guys don't think that's needed at all, as the MM is safe, gantry won't come off the rail, but still, would it be an electrically feasible alternative for a protective system against derailments? of course, considering that we could somehow isolate the wheels from the gantry itself. regards, francis Last edited by sprayhead; Wed 20 January 2010 at 04:29.. |
#227
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Francis,
The question becomes is the work involved necessary for the number of times that the machine derails. I have never had my machine derail. The proximity switches will stop the power if you derail. But the other question I have is, what will you be able to do even if you have a system in place? You system will only sense that you have derailed. It isn't going to stop the derailing. I think you have to be going pretty fast to derail. |
#228
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Francis, such a system will cause huge frustration........one speck of dust between the rail and roller and the system stops cutting.....
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#229
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Nils,
My derails usually happen when a shop rag was left on the end of the machine and rollers ran over it! Thus causing just enough of a distance gap between rail and sensor to fault the machine. The main reason for adding cow pushers to the gantry for the x rails. Francis, Good idea in theory...most likely will drive you bonkers in clinical practice. Good day. Sean |
#230
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Thanks all for the responses
Indeed using the actual wheel as the contact point will probably drive the operator off his chops. Perhaps using a brass brush as a rail scrapers and using that as the contact. I think I've seen cheap small brass brushes for sale on autoshops, it might be an idea. But, the proximity sensors are great aren't they. Another question, how far from the steel do they start reporting an open circuit? francis |
#231
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Francis.
The sensing distance varies on the quality and type of unit. Mine sense 0-3mm. Thus, I set them to "just be active" closer to the 3mm distance away. 3.5-3.75 mm activates the derail fault. |
#232
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Sean,
That's great news! thank you. 3mm is such a small gap, these things are very sensitive. I'm starting to like very much these proximity sensors Just one more question... (an affirmation first)... When the sensor rolls over the hole it opens the continuity of the circuit and mach3 reads that active low signal and stops the gantry, abruptly. (question) To carry on with the cutting, do you just Jog out of the hole? But if the sensor goes past the hole, with the inertia of the gantry when stopping, mach doesn't just carry on right? I take that it faults for good. thanks, francis |
#233
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Francis,
If you have the limit switches set up correctly with Mach, the software will warn you that you are going to have a limit problem when you start your cut. So you should not be running past the hole with the limit switch active and hitting the stops. |
#234
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Quote:
and It seems that you can adjust the distance of the sensors ... from my understanding (no hands on experience) is that they are sensitive enough to trip in case of an obstacle on the track... or some other unforeseen reason. And BTW, thanks Sean for your answer to my question which I have had since first reading the Mach 3 manual... |
#235
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Guys, I did see that someone wrote about reed switches, and that they weren't the best option for the MM.
What was the reason again? I suppose that for homing and limiting purposes they would be good, wouldn't they? I have seen them in Normally Closed electrical configuration from General Electric company. It's just that they seem a lot easier and simpler than proximity switches, for wiring. I have read the whole thread a few times and I am still not sure what's up with the proximity switches... what signal comes out of them and why and how to connect each proxy to a relay. Francis Last edited by sprayhead; Sat 23 January 2010 at 22:00.. |
#236
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Francis, I'm in the learning process too, I treat the proximity switch as a switch & they need a DC voltage to work. The proximity switch don't "send" signal but the BOB input port "detect" a ON (1) or OFF (0) condition of the circuit.
Hope this helps. Last edited by KenC; Sat 23 January 2010 at 22:38.. Reason: eleborate on the point |
#237
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Proximity Sensor Explained
This is the way I keep track of how the proximity sensor works. The diagram that comes with the sensor is confusing. Hope this helps. This is the NPN NO Style.
Interlocks of this type should always be wired FAIL SAFE. This means that if a cable is disconnected the machine will sense an error. Normally Open (N.O.) contacts usually give this fail safe condition. |
#238
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Thanks for sharing, its really helpful.
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#239
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this ebay seller sells proximity switches and solid state relays, anyone purchased from him already?
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#240
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I am also looking into his prox switch too, specs look ok...
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