Sean,
Everything was making perfect sense until this part.

What NO contact ? Am I missing something in your schmatic?

Sean

I wish you guys would have these talks on the threads because I am sure that others like me would like to be able to understand this stuff. I want to understand how these things work. I am learning many things and I hope once I get my machine built and running that I will be able to share some of my software experience.

Greg J,

I was waiting on Sean to answer this one but it looks like he's signed off so let me see if I can answer it.

The prox has a normally open switch inside it. When the circuit is energized, it closes as long as the metal rail is in front of the sensor. That's the way I understand it anyway.

Will someone please check my work before Mr. Richards starts designing a circuit.

Push button station 1 (On Car)
Red PB (NC) -> J6 Estop
Red PB (NC) -> Contactor
Green PB (NO) -> Pin 15
Yellow PB (NO) -> Pin 13
Black PB (Gerald, I can't remember what you had in mind here. I think it was for the Z zero.)

Push button station 2 (On Gantry Front)
Red PB (NC) -> J6 Estop
Red PB (NC) -> Contactor
Green PB (NO) -> Pin 15
Yellow PB (NO) -> Pin 13

Push button station 3 (On Gantry Back)
Red PB (NC) -> J6 Estop
Red PB (NC) -> Contactor
Green PB (NO) -> Pin 15
Yellow PB (NO) -> Pin 13

Z Prox (NO) -> Pin 12
Car Prox (NO) -> Pin 12
X Front Prox (NO) -> Pin 12
X Back Prox (NO) -> Pin 12

Z Zero Plate (NO) -> Pin 11
Probe (NC) -> Pin 11

Thanks Doug,

I think that does help.

The Prox. is NO, but since it see's the rail, it activates (sorry if terminology is incorrect). Since it's "activated" (closed) the solenoid in the relay is energized, closing the latch in the relay.

Now, under normal conditions, all three relays are closed, because the Prox. sensors are seeing the rail and are closed. When the Prox. see's the hole at the end of the rail, it opens, de-energizing the solenoid in the relay, opening the latch. The BOB see the new condition and knows it's at zero (if ref all) or in a fault (if gantry de-rails, or whatever).

Aaaah, light bulb is starting to glow.

Does that help Nils?

Sean, where does the +-12vdc come from?

There was a good question in here last night, which the poster shyly decided to delete again:

"I am trying to wrap my head around the layout and wiring of either proximity sensors or the switches. I take it that the main purpose of these is to allow mach to be programed to set the router in a home position in all three axis's.

Okay if that is the goal, I do not understand wiring three or four sensors in series NO would work. Reason being, how does mach know which sensor tripped when they are all in series? "

Your car is parked in your garage and the garage door is closed. You get in the car, start the engine and you are now going to drive. Your name is Mach3, you are blindfolded. You (Mach3) puts the car in reverse and drives. Mach3 hears a bang, (the garage door is hit). Mach3 puts the car in Drive, goes forward and hears another bang (the front wall is hit). Mach3 being a normally bright person has figured out that the bang after reverse is the door and the bang after Drive is the front wall. Mach3 only needs one bang sensor.

On the router table, you can wire everything in series, to make one big sensor, because Mach3 is smart enough to know what it was doing before it hits this sensor, and therefore figures out which part of the sensor it hit.

And then, to give some perspective, this bit:
"I take it that the main purpose of these is to allow Mach to be programed to set the router in a home position in all three axis's."

The reason we manage to mostly get by without any switches is because we "home" the machine to the corner of the material lying on the table. After changing a cutter, manually jog the cutter over the corner of the material and set x and y to zero from the keyboard. Then jog the cutter till it just touches the surface and set z to zero. Then start the cut.

A home switch on the z-axis can never tell you the distance between the cutter and the material. Home switches on the x & y can only tell you the distance to the material if the material is located to the same spot everytime.

But there are times (not many) when we wish we did have proximity switches . . .
- When there has been a glitch (power failure?) in the middle of a sheet of material and we need to find the reference points again.
- When the cutter hits a clamp and the car jumps off the rail.

Nils, we are not getting into lasers. . . . yet.

(Besides, from the little I have read, lasers often need an analog ramp up/down for engraving, to avoid burning through when motors are accelerating/decelarating.)

Gerald,

You misunderstood..... I am not getting into lasers for cutting. This the crosshair laser.

Discussed here: http://www.mechmate.com/forums/showthread.php?t=596

Hope that clears that up. I have my hands full just trying to understand the router build. I could have made it clearer and said crosshair laser.

We need an output for the crosshair laser. NC -> Pin 14

Gerald,

I think Nils was talking about a laser pointer like Greg (Down Under) has set up on his machine.

Doug mentioned it awhile back on another thread, but I think it's worth repeating.

Mach has a great tutorial video on coordinate systems that explains this homing / zeroing / etc.

http://www.artsoftcontrols.com/Video...elections.html

The crosshair laser is only fed with a battery.

Gerald,

I respect your knowledge and your design. But Greg Greolt has a cheap less than $5.00 crosshair laser that he uses on his machine that he turns on and off with a button on a Mach3 page. I don't believe it is powered by a battery though I am sure there are battery versions out there.

I am getting the feeling that you don't like this idea so you will not hear any more about from me.

My impression was that you need to stand close to the laser to line it up with a mark on the job - that's when you just switch it on. Some of these lasers have the battery and switch built in (keyring type, board pointer, whatever, (shooters pistol type?)). Using mach to turn it on seems like an overkill.

Sorry guys I posted and deleted the question above that Gerald reposted. Reason for deleting is that I wanted to think about it some more before asking that. Since I posted that Sean has answered it for me.

I was seeing the layout with the three relays NO and the sensors NO. What I failed to think about yesterday was when the sensors are powered up and see the rail the go NC and the relays go NC, which closes the open circut from common to pin #11. The when any sensor trips it opens the closed circut giving a signal to the BOB.

I get it now. I knew Sean had his working and it was something simple that I just wasn't seeing or grasping yet. Thanks for the replies and explaining better.

I see exactly what you are saying also Gerald, It would be hard to have the same thickness and size material placed in the exact same place every time, and if your memory is like mine it would be easy to ruin alot of material or break a bit or worse by not manually setting it for each project.

I think I will use the sensors but for more for safety than anything else.

I agree Gerald. I worry that we may be making the MM electronics too complicated. That may discourage new builders from taking the leap and later on when my machine breaks and this info is no longer in my head, it will be harder to diagnose. At most, I would use simple push on/push off switch mounted on the car to turn on\off the laser pointer and some wires to supply power. Better yet, run it off the battery.

http://www.uie.com/articles/simplicity/

I hate batteries as much as the next guy, but we can't design an input to a laser pointer if we havn't got a clue what it needs. I am fairly confident that a 12V DC supply to the gantry could be converted for use by the laser pointer and that a simple local switch could control it.

bump

I guess what I'm asking is did you add another output to your power supply or did you draw power from somewhere else?

He gets it from his Antek supply

how many times can you tap from the same 12v output? I still have to order my power supply so maybe I should ask for two 12v outputs instead of one.

I don't know if this has been cover but here is an idea for switches that works great. I use them on my minimills the ih mill, my minilathes and my
12x36 lathe. not one problem amongst them. It is an easy setup with common parts.

http://www.industrialhobbies.com/how...limits_pt1.htm

http://www.industrialhobbies.com/how...limits_pt2.htm

http://www.industrialhobbies.com/how...limits_pt3.htm

the working part http://search.digikey.com/scripts/Dk...me=QVA11134-ND
and last is a post about the setup at cnczone http://www.cnczone.com/forums/showth...=optical+limit

hey guys
been working a little late and saw the comments. The 12v comes from my antek transformer. I ordered it with 12v 5v and 56v taps all voltages are redistributed thru dinnectors power blocks for use. Mainly to preserve wiring standards from gecko. The 12v is used for the pmdx and now the prox's. 5v for the ncpod later.

Ed, I am so glad the wiring use finally "clicked" in your head. Don't hesitate to email me with any other questions. I am glad to help those that are trying to build the machine.

The relays and simple wiring was really easy. On mm #2 I will relocate a wiring block and power distribution to the gantry. It will greatly simplify my big blue box.

Chris, your switches could be technically okay, but they are not readily available off-the-shelf around the world, so I can't include them in the design. Do you have dust seals where the rod enters the housing? Also, we would loose the jump-the-rail-protection that the proximity switch gives us.

Looking back at post #70 where Gerald posted a drawing that showed various input devices connected to a box as well as an output connection going to the control box, we still need to define the STATE of each input and we need to define which output line each input uses.

By STATE, I mean the Active State of the device. For instance, the State of an Normally Open proximity switch when used with the MechMate would be Normally Closed or Active, since the usual condition of the proximity switch is to sense metal except when a limit has been reached (the hole in the metal). So, if I knew that there were going to be four proximity switches on the machine and that all of the proximity switches would normally be turned on and that all of the proximity switches were NPN signal type, I could easily design a circuit that monitored the proximity switches (or relays to which the proximity switches were connected) and then generate the proper signal for one of the signal lines going to the control box (pin 11, 12, 13, or 15, or even the E-stop signal line - if desired).

The same goes for the push-buttons. Are they Normally Closed or are they Normally Open? (Normally Closed is safer because a broken or faulty push-button would be detected as the machine powers up). When they are active, do they give a 12V signal or do they give a GND signal (0V)? A circuit designer would say that a switch giving out a 12V signal when it is active is SOURCING and that a switch that is at 0V when active is SINKING.

If I were building the most simple and the most robust interface, I would use a series design for the proximity switches, just like Sean's in post #67. I would use Normally Closed push-button switches connected in series for each of the different push-button circuits. The zero plate would be a Normally Open configuration, because that would be the most straight-forward. By wiring the proximity sensors in series (through relays), if any sensor 'detected' a hole, the input state for the sensors would go from 0V to 12V, signaling that a limit had been reached. In the same manner, if any one of the Red push-button switches was pushed, the circuit would be 'broken' and the input signal for the Red circuit would go from 0V to 12V, signaling that at least one of the Red switches was active. The Zero plate would be just the opposite. When contact was made between the plate and the cutter, the input signal would go from 12V to 0V, signaling that contact had been made.

Of course, using more complex circuitry, any input (switch or sensor) could be either High or Low, On or OFF and gates inside the box could be jumpered so that the correct signal was sent to the control box, but that would require much more circuitry and it would also give the builder many more possibilities to mess up by jumpering something backwards.

So, who wants to define the STATE of each device?

I'll take a stab at that too. Unfortunately, I'm going to be tied up with work for at least a couple of weeks so I probably won't have a rapid response.

Craig, I will take a crack at answering your question.
You can run as many things as you want off the VR as long as the max current draw from the items that you are running off the VR stay under the current rating of the VR. Say if it is a 1amp VR, add up the current draw from everything you will connect to it and it needs to be under the 1 amp. If I remember correct from the PMDX literature I read, the PMDX draws a maximum of 300mA (if this is wrong someone who knows will correct me) I don't know what the proximity sensors draw, they also have some small LED's. Check the total amps they draw and add the 300mA that the PMDX draws, then check the amp rating on the VR.

EXAMPLE:
PMDX 300mA (check to make sure)
Proximity Sensors ??? maybe 120mA (just a guess check to make sure) X4=480mA
Laser pointer ??? guessing 100mA (check to make sure)

880mA would be 120mA under.:):)

If you were to add an array of superbright LED's (like I want to do) under the gantry to light the work area, then you may need an alternate source of power. The superbright LED's draw 100mA, so 20 of those under the gantry would draw 2 amps, but would brighten the work area very nice.:D:D

Thanks ED, Thats what I like about this forum, Lots of help!! yours was actually the 3rd answer I received thanks for looking out.

I have the proximity sensors now and they draw 200mA each and I checked the PMDX and it draws 200mA max. So if the redimade antek supply has a 1amp voltage regulator on it, you will be at 1 amp if you use 4 proximity sensors. So if you add anything else you will probably need an alternate source of power.

I also added a question in the power supply about this subject (moved back here):

"Gerald, this brings up a question to you, for those who are using the pre-made voltage supply from Antek, with the Voltage regulator to run the PMDX. If they also run 4 of the proximity sensors also, that will be using up 1amp of avalilable current for the motors. Will adding the sensors in addition to the PMDX be any reason for alarm?

I am using the 2amp 12v supply from factorymation, but thought it would be a good question to talk about."

What is making your proxies draw 200 mA? Did you measure it?

Here is a typical spec sheet:
http://factorymation.info/sensors/Inductive.pdf

They draw less than 15 milliamp by themselves (if they were connected directly to the PMDX for eaxample), so the 4 proxies by themselves are extremely light on current consumption.

However, they can drive up to 200mA each, and will do that if you have a fairly "big" relay on each one, that is mostly in the energised condition.

So, to keep the current consumption down, either:
- drive logic chips instead of relays
- if using relays, use low-current relays
- if using relays, consider using them mostly non-energised.

Alternatively, size for a bigger power supply.

If you are using this relay:
http://catalog.tycoelectronics.com/T...23079A1003B301

which has a 1029 ohm coil resistance, it will draw only 11.6 milliamp at 12V. Therefore, 4 proxies and 4 of those relays together will be close to 0.1 amp, which is no cause for concern.

No I didn't measure, just going off what the data sheet that came with them said that they draw.

They do have four small LED's though.

I think you might have misread the data sheet ;) At that sort of current they would be getting quite warm . . . .

They have the ability to drive that much current, but you shouldn't be using them near the limit for this application.

See post #32 in this thread for info on a relay choice

Maybe you are right. Seems like alot considering the size of the LED's. A small LED draws 20mA and these look like about 3mm.

Here is what was on the wiring diagram....exactly the way they wrote it.

10-30VDC I=200mA

Usually it will give a max current draw but that was all that it said.

Those relays look good, thanks Gerald.

Looking at those relays though brings me back to the original point or question though, for those who are using the voltage regulator and also the sensors. Not trying to be a pest about this or anything just trying to make sure that those using the voltage regulator off the transformer are aware of the current draw when adding additional circutry like the sensors and relays.

I didn't even think about the draw from the relays and they will be drawing anytime the sensor sees rail to keep the contacts closed. The ones at mouser draw 140mA each.

Doodling a little PC board for relays for the proxies:

ED, check that Mouser spec again - it is 140 milliWatt.

Of course your point is valid - the power supply must be sized to feed all the consumers.

A 300VA supply can feed about 2000 of those relays if it has nothing else to do. :)

oops your right Gerald it is mW rather than mA.

Nice drawing I will save that. What cad program are you using for drawings like that?

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