Sergio.
7 core is for the pause, estop and resume buttons. The 7 core does used a shared ground for electrical connections to pins 11, 12, 13 and 15....with a common ground.

The proximity circuits are outside this requirement. Pending your choice on limits/prox sensors, you will need additional

Robert correct me if I am wrong, but the optos are not in the circuit to provide isolation, but just as a quick 12v to 5v conversion. Therefore sharing a ground is not a problem.

Well, my supposition came frome post n°122 in this thread:
http://www.mechmate.com/forums/showt...&postcount=122
ciao

Sergio, if you wire it that way...your good.

I was concerned you were trying to put the M12 connectors and their power on the 7 core cable...which would leave you short a number of strands.
Personally, I prefer to run 12 core....those extra cores have saved my rear lately when a core breaks or I want to add that little "laser or duty purpose button" out on the gantry.

Proximity Target M1 18 027. Where does it fit?
 

I'm contemplating making proximity target M1 18 027
It's listed as fitting to the car stopper M1 18 000, but I can't see where.
I'd appreciate some guidance on whether to make this part and where to install it.

Bright flash: These fit into the 20mm diam holes in the rails and can be turned to tune the proximity switches? In which case the correct higher level drawing for M1 18 027 are 10 10 246 and 10 20 246? If this is the case, do they get glued in place somehow? Won't vibration let them shift?

Your « bright flash » will serve you right !
As for my opinion & method I’ve practice on this, I’ve made a smaller hole ( 18mm) hole on the underneath beams to serve as a “through hole stopper” for these eccentric discs . This way, this M1 18 027 will not fall through !
Then, in the rail, they can get fixed in place by means of “gluing then” with slow set silicone, after making sure they are in correct position.

Not something I can recall being exchange / discuss much here …. Or maybe I too getting affected by age :o

Amicalement, Robert ;)

I real world use, I have found no real need for the disk if your not using the "auto squaring" feature in Mach. The open hole is for two things:
- homing machine
- end of travel "soft" limit

The homing can be resolved to an accurate position with home offsets in the settings in Mach3.

If you want to use the autosquare feature, then the holes in your rails will have to be "dialed" in as the disk/hole method suggests. It's a nice feature in the MM design, I just never really had a use for it.

Sean

Today I tested this config with a PMDX125 BOB and it work as PMDX says, without extra interfacing, I used it for a spindle sensor and it worked like a charm at 1300RPM. Even the color cables were the same!

John (Zigmart) had some boards made based on the scematic in post #38 of this thread of which I purchased one. For whatever reason my proxies (AECO NPN NO purchased at factorymation.com) would not work correctly with the 74LS08 AND logic chip. I had to use a 74LS32 which uses OR logic in order for the proxies to trigger the correct output.

Any idea why that would be? Thanks.

BTW: Proxies rock! At least for me. :)

Actually this is doing exactly what Mike designed it to do. He wanted all the inputs to be in an "open state" so when one sensed a target at the limits, it triggered the circuit ( 3 off, 1 on).

Unfortunately we want them to all be sensing metal for the whole run "closed circuit", switching to an open state at the limits. ( 3 on, 1 off)

Glad you found a work around, and I will be doing the same to get mine working.

Thanks

Tks, John. I had not considered that he would design for seeing targets instead of always seeing metal. By wanting to be able to sense the gantry lifting in addition to the home/limits I had to use "OR" logic. Luckily there was a "drop in" replacement IC with OR logic.

I plan to post some pictures tomorrow of my proxy board installation.

Sorry, guys. My Shopbot had targets. Your MechMates have holes. The designs are opposites. The 74LS32 chip uses "OR" logic which is opposite to the 74LS08's "AND" logic.

I replaced that design a long time ago with another design that uses a microcontroller. That little 20 pin computer allows me to use a jumper to select whether a proxy is normally On or whether it is normally Off.

I would probably give you my first born to get ahold of that circuit :) (he has a strong back, and follows instructions most of the time, but he eats ALOT)

Here is more input on the wiring of proxies from Steve Stallings at PMDX. PMDX have a guide sheet pending, but it's been a while in arriving. My question reflects my lack of knowledge. Apologies to Sean for using his circuit as a comparison, but I was struggling to get my head around the wiring. I hope the info helps others.

> > Hi Steve,
> > I'm having trouble finding a
> > specific answer to wiring proximity sensors that I can use for homing
> > and limit switches (I've been anxiously awaiting the app-note for a
> > while now, but I realize that you have other things that need priority).
> >
> > I see in the PMDX 125 Users Manual that the NPN switches are set up in
> > parallel (Figure 4 in Section 6) and wired to a single input on J12 or
> > J13. However the best info I can find off the user forums is for a
> > series connection as in the attached pdf. (Note: the circuit diagram posted by Sean earlier in this thread)
> >
> > I just wanted to
> > confirm that the circuit shown in the Manual is correct.
> > (or are the two diagrams the same and I'm misreading the load?)

REPLY:
If you have NPN type sensors with N/O (normally open) outputs,
then the diagram in the PMDX-125 manual will work fine.

The diagram shown in your attachment also used NPN sensors with
N/O outputs, but added relays. This does provide isolation between
sensor power supply and the breakout board, but I do not know
why the builder decided this was necessary. His design will
work properly, but it is more complicated. Please note that
he must be using relays with normally closed contacts, even
though he does not say this on his diagram. He may have been
trying to follow the failsafe series wiring approach, but this
really does not work in his case since cutting a wire between
one of his sensors and the relay would go undetected as would
a failure of the 12 volt power supply. If he had used normally
closed sensors and normally open relays, still in series, then
the circuit would be failsafe.

You should also be aware that the circuit in the PMDX-125
manual produces an active low signal and the circuit in your
attachment produces an active high signal, so your CNC software
must be configured accordingly.

If you actually have a PMDX-126 instead of a PMDX-125, then
the above still applies, but you could also use PNP style
normally open sensors with the PMDX-126.

Normally closed electronic sensors such as proximity sensors
can also be used with any breakout board, but their outputs
cannot be directly wired in parallel or (for most sensors)
in series. If one had a supply of normally closed sensors,
then using relays would allow you to use more than one to
drive a single breakout board input.

Regards,
Steve Stallings
PMDX

Steve's notes are correct.
I choose to wire mine specifically this way so the interaction with the MM rail (so it detects a derail situation within my logic profile designed into my system) The machine will not operate in my scheme without all the sensors active and working.

Each works - just remember that the sensors are always ACTIVE during operation and fault out...like an estop

Good luck

Sean

Thanks Sean. Since I really don't follow these circuits I needed further clarification. I posted Steve's reply because I hoped it would help other people. Thank you for your clarification.

Proximity circuit difficulties
 

I have NPN N/O proximity sensors J12M-D4NK (it's possible that the label is incorrect and they are J12M-D2NK or J12-D2NK).They are rated 10-36V, 200mA and 4mm. My search on the code only turns up Chinese sites.

I have them wired to ports 10 and 11 and the 12V output on the PMDX board.
The "Autodetect" feature in Mach 3 /Config/Pins and Ports can to detect a single sensor and the home and limits work fine. When the sensor fails to see metal it triggers an error state.

But when I connect a second sensor in parallel as per the circuit in PEU's post of 18th Feb 2011, then the sensors fail to switch and Mach 3 error states are never triggered.

Is this situation familiar to anyone?

Red, I had, incorrectly, assumed that it would work with the PMDX-122 board. As soon as I paralleled two sensors it quit working correctly. What board are you using?

Jim,
PMDX-125

We're using proximity sensors to sense the absence of metal (the hole), so that's "not proximity". So the normal state of a "Normally/Open" proxy on a MechMate is "not normally open", known as closed, meaning that it's really a "Normally/Closed" sensor as we use it.

N/O switches are wired in parallel, but N/C switches are wired in series. So the reason that paralleled sensors aren't working is that one of them is always conducting, so you can't see the changes on the other one.

Proxies are a little more electrically complex that a simple switch, but they can be daisy chained with a little careful attention ( one example )

Red, I ended up getting a pcb patterned after the circuit that appears earlier in this thread and I am thrilled with it's performance. I had to change the logic chip in order for it to work on the mechmate but that was a simple substitution. Thanks to Mike and PEU for their work on this!

Red,
Thanks for the note. I hope all the input has helped you understand the proximity switch/sensor needs for your application.

The proximity (act like a switch) but do have there own specific requirements with relation to the MM. On occasion, it takes a few minutes to explain to board manufactures the "not proximity" state the MM is looking for with respect to the rail design.

Good luck on the rest of your build!

...I'm quietly getting ready for my 4th build, so these discussions are prudent!

Best

So, if I understand, the preceding 3 posts, I could put a raised piece of steel at each end of the axes instead of the holes and raise the parallelled N/O sensors to be out of range when the machine is within limits, but triggered when the proxy's sense the raised steel at machine limits? Of course this will not detect a derail...

Or I can wire the proxies in series so that the circuit detects a break. If I followed Gerald and others posts earlier in this thread Mach 3 will be smart enough to figure which of the sensors must have triggered based on the direction being moved at the time, even if all axes are wired to one BOB port?
But then I need at least 40vDC for the series circuit?

You may be able to make it do what you are saying.....but one important feature of the design (reason it is wired as it is)is that if the gantry jumps the rails the sensors will lose proximity and prevent damage. If you wire it as you are thinking it would work for homing but not an emergency such as a derailment. IMHO but others may correct me if I am wrong :-)

Are relays needed?
 

I have read and re read this thread but still confused as to whether relays are necessary in the proximity circuits.
Red’s post 294 (including Steve Starlings reply) and Pablo’s posts 274-288 suggests that with the PMDX 125 and 126 Bob Npn and Pnp N/O style sensors can be interfaced directly to the board without additional components. Is this a viable alternative option for the MechMate? Or am I missing something fundamental that requires relays as per Mikes-Sean’s diagrams?

Tony,
No need for relays if you run a parallel circuit using N/C switches (i.e. the circuit is closed when the sensor is "seeing" steel, and then open when they reach the holes in the rails). The 12v port on the PMDX125 easily powers the four 10-36v proxies in parallel.

If you have N/O switches and a parallel circuit, then you have to reverse logic so that one of the parallel circuits closes upon error (i.e. have the proxies 'not see" the rail during operation, and put a steel "step" at the end of the rails that triggers the switches to close).

The latter has problems if your gantry jumps a rail because it's not as sensitive to this error situation (but an argument could be made that one of the gantry proxies will "see" steel in a derail situation). I have gone with this setup as an interim measure until I lay my hands on some N/C proxies (because I can't determine whether mine can be made N/C by switching wiring around).

If you have N/O proxies and want to use the holes in rails to trigger an error situation, then you need to wire the switches in series so that the series circuit is broken when one of the proxies sees a hole in the rail (i.e. goes to closed). Assuming your proxies require 10-36v and you have 4 in series, then you are going to have to do something in order to supply sufficient power to them. This is where the relays come in because they can provide the power step up or down together with optical isolation. Optical isolation comes free when you use power off the PMDX125

It took me an age to figure that the proxies can viewed as switches (the 3 wires and internal circuitry made them seem "magic" to me). Once I figured that they were switches it was easy for me to understand what the circuits were doing.

Red,
Thanks for that explanation. It looks like I can avoid the complications and extra wiring of relays by using N/C switches in parallel wire directly to the PMDX126.
Once again thanks

Tonys
Careful - I didn't think this one through fully! One open switch in an otherwise closed parallel circuit won't signal anything. For a parallel circuit you have to have the circuit open and then a closed switch in part of the circuit will trigger a signal. Apologies. It took lying awake in the middle of the night to see the error.

Red,
Sorry to cause you sleepless nights! I can now see that a parallel wired N/C circuit would not detect a fault if a proxie is triggered. As I understand it, I can use a N/O circuit with proxies in parallel (as per the PMDX 126-125 diagram), if I provide a metal target to trigger the proxie rather than a hole in the rail. The disadvantage in this system is that it may not detect a derail situation.
In believe you said this is your current set up, and wondered how well you thought it was working? Or have you plans to change it?

Tony,
This is my current set up because I had to get home switches working so I could figure out Mach 3 (I'm an absolute newbie to driving a CNC). The system is working. I have all himing and limits connected to a single port on the PMDX125. I can home and have begun to learn how to drive the machine.

If you now re-read Steve Stalling's response to me and look at Sean's circuit everything they said should now make sense.

This discussion seems to require one on the frequency and conditions for derails?

Looking for a little help.

I have proxys 1 for each axis. And I bought the winford relay board Sean talked about in post 49. My problem is I can get each to work independantly, but when I try to wire them parallel, they don't work.

I've been waiting a couple years to use homing and this is driving me crazy.

Any help would be appreciated.

Mike

Are they normally open, or normally closed? If they are normally closed, they won't work in parallel. Can you tell us a little more about the proxys you have?

They are the SI12-C2 NPN NO H

Everything depends on the way that you use sensors. When a Normally Open sensor "senses" metal, it closes and when it "senses a hole in the metal, it opens. So, on the MechMate, we could say that in normal operation, the sensors are in the normally closed state because they all always sense metal until the axis hits the "hole". If the sensors are wired in series, then if ANY ONE of the proximity sensors senses a "hole", it will open the circuit, indicating a fault condition.

Keep in mind that most proximity sensors work at voltages between 10VDC and 24VDC. Each sensor will drop the voltage by 1 or 2 volts, depending on its internal circuitry. Because of that, I would use a 24VDC power supply. (My preferred method is to feed each sensor into a logic board and then use a microcontroller or a logic chip to decode the status of each sensor.)

I think I see the point. The proxys are closed while seeing the rails and go to normally open when they see the holes. So they should be wired in series. I'll give it a try.

Worked like a charm.

Thanks Mike for a thinking answer. Thanks for pointing me.

Mike,
Looks like the team took care of you before i could get here tonight.
Glad to see you have the "logic" correct for the relay assembly.

Sean, I got quick responses. Thanks for jumping in. I just needed to be righted.

The people on this forum have always been great.

proximity sensors
 

Received my proximity sensors yesterday wired them to a 9v battery and they seem to work ok would they be any advantage in using 24volts as i have a 24volt estop relay i might use once i figure the estop out.:confused:

What will you do with your signal voltage? Does it need to be in the 5volt range? For example, say at the computer logic level... :cool:
Not sure how the work, but it appears that the supply voltage is also the reference voltage. So if controlling a 24v relay, it should work great!