Limits, homes, override switch

Hello, it's me, I was wondering if after all these years... alright let's get serious :D

1. In my control cabinet, I have a limits override DPDT switch. Works like a charm, but only for the limits, since I didn't connect the homes to it... so when one of the home switches triggers, my override switch is useless. Was I supposed to connect also the homes circuit through the switch as well ?

2. In Mach3. I have homes on pin 13 and limits on pin 15. Am I supposed to use pin 13 both for homes and X-- and pin 15 for X++ ?

Thanks for your help :)

All the best,
G.

I thought it could be possible to use the DPDT switch I already use for the 24V limits circuit:
Attachment 17677
... but since the homes loop is 10V, I can't wire in on the same side of the DPDT switch as the limits. I would have to put it on the second side, but the buzzer is already there. I wanted to put the buzzer on the same side as the limits, but it keeps beeping, since no matter what pin I connect it to, it'll always find a way to the negative side of 24V PSU. Therefore it's a dilemma.. either I have to get rid of the buzzer to free the second side of the DPDT for the 10V circuit, or I just get another DPDT switch for the homes.. but that seems a bit annoying as I would have two limits override.. so I think getting rid of the buzzer is the way to go, but then how do I got about not forgetting to put the switch back to it's OFF position once I've jogged the machine off of a triggered switch ?

Hi,

Now I am going to try and clear a little confusion (or add to it ?).

Homes - are basically positional references.
Limits (which are normally a little outside of homes) are the protection to stop you jamming the machine and/or damaging it. It is llike hitting E-stop in principle.

Mach3 when it does the homing, jogs the axis until it encounters the home switch and then moves back off the switch to a place where it is not triggered. Z axis is lifted to Home first, to raise the tool above the workpiece (usually:cower:). Then the Y and X, but the order is configurable.

So you need separate pins for Homes and Limits, as a triggered limit demands operator action to correct. You have to disable the triggered input manually first before you RESET Mach3 and then jog back to safety. You can then switch the Limit back into protection mode.

I use a buzzer to indicate that I haven't completed the process properly.

You can always use a 3PDT switch like this one below. BUT you don't need any reset for Homes if you keep them on separate input pins.

Cheers,
Rob


http://uk.farnell.com/multicomp/mcr13-432c1-01/switch-toggle-3pdt-on-on-sq/dp/2128057?ost=2128057&mckv=Pet0r2EX_dc|pcrid|7810829 0589|&selectedCategoryId=&CMP=KNC-GUK-FUK-GEN-SHOPPING-MULTICOMP&CAGPSPN=pla&gclid=CMad8Mvji8sCFQjlwgod3v IHHg&CAWELAID=120173390000201411&gross_price=true

Quote:

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Originally Posted by cropwell

You can always use a 3PDT switch like this one below.[U] BUT you don't need any reset for Homes if you keep them on separate input pins.

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No Don't use any relay for Home switches just connect direct to the Input pin or pins. The Relay cause a delay and makes homing unrelaible.

You can share one Input for all Home switches provided you use the correct switch type and connection.

If your wanting to share the Switch for both Home and Limits then you can't using the Relay approach for the above reason.

Hi,

First - What switches are you using for homes and limits ?

The 3 wire Inductive type of switch usually floats (no connection) or grounds the switch contact depending on whether NC (normally closed) or NO (normally open), The fact that you use 24v or 10v to power the inductive sensor doesn't matter.

NC are normally wired in series with the first switch being connected to actual GND and the next switch getting its GND from the preceding switch NC contact, with the last switch in the series having the NC contact going to the BoB. This means that if any one switch is triggered then the input to the BoB goes to 'float' and circuitry inside the BoB lifts it to logic 1 (active high).

NO are wired in parallel, so that if any one switch is triggered, the input to the BoB is forced to GND (logic 0, active low).

As Jazz says relays are unnecessary and cause errors in Homing precision.

NC switches are preferred as they fail to 'safe' if you have a circuit break.

Cheers,

Rob

Quote:

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Originally Posted by eurikain

1. In my control cabinet, I have a limits override DPDT switch. Works like a charm, but only for the limits, since I didn't connect the homes to it... so when one of the home switches triggers, my override switch is useless. Was I supposed to connect also the homes circuit through the switch as well ?

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No like said in last post Homes are separate to limits when using Relay.

Quote:

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Originally Posted by eurikain

2. In Mach3. I have homes on pin 13 and limits on pin 15. Am I supposed to use pin 13 both for homes and X-- and pin 15 for X++ ?

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Again No 13 is Home switch and it doesn't have ++ or -- It's just a switch you place at one end of the machine then tell mach to head in that direction when looking for the home switch.

Only Limits have ++/-- because they watch both ends of the machine.

When using Home switches it's normal to use NO switch type because the switch is only triggered at the point of homing. That said you can use NC if you like but the Led on the switch will be on all the time.

Alright, so let me explain the current situation. Look at the diagram I've posted above, there are six switches. They are all those black mechanical switches with three pins (COM, NO, NC). I have connected the EXACTLY like on the diagram, which means: two separate circuits. I guess I misunderstood things when making the diagram a few weeks back. So, if I understand well, you actually need NINE switches ? 6 for limits and 3 for homes ? I've only got six switches, so I guess I can't have homes currently. Is that an issue really, or can I just have a virtual "home" ?

As for the NC / NO setting, no worries, I've got that in :) The 3 limit switches that I currently have work great, and I can use the DPDT switch correctly to manoeuvre the machine when one switch is triggered. I've done it a few times now.

So, I guess I'll just have to connect my three wrongly-supposed-home switches to the series loop of the limit switches. Therefore I'll get my six limits in series and I just won't have homes. However, how can I physically have home switches AND limit switches ? When the machine moves, it will crunch/bend the home switch before it can reach the limit.

Jazz can probably explain it better than me, but you can use the same switches as home and limits as Mach3 can disable limits when homing.

Microswitches are cheap enough (I don't pay more than €2 each) and it looks as though you have standard microswitches, so forget what I said about inductive sensors.

It is not usual to have a Z-- switch. If the object of the Z-- limit is to stop you crashing the tool into the machine bed, you need to know the tool length, so Z-- is pointless.

You should arrange the switches so the actuating is not done by end on contact, but by an arm passing by the switch. That way the switch won't get crushed.


I haven't looked in proper detail at your wiring diagram, but my first impression was that it was over-complicated. I can't understand why you are talking about 10v and 24v as the BoB input pins are 5v, any higher and you could fry the board.

Estop should kill power to the drives and VFD and report to Mach3 that an Estop has happened, which is what you have.

Cheers,

Rob

You can and you can't share the Switches for both jobs.???? . . . . . . You can if you don't put the switches thru the Relay. The relay is a problem for Homing because of delay which you don't want.

If you want the Limits to run thru a relay then you need separate set of switches for homes.

Now personaly I don't have problem with running Limits straight to inputs provided the input can accept 24V to lessen chances of noise. Lots of BOB's are 5V only so this why relay is used so can still run 24v thru the long path to switches but keep the 5v signal line short and lessen chances of false triggers etc.

If your BOB can take 24V then Mach will allow you to share switches to do both Jobs.
So if you want Home switches (which I suggest you do) and don't want to fit extra switches (which I suggest you do) then remove from going thru the relay. Just keep relay for emergency stop.

End of the day Limits are Not Emergency stop but rather positional loss and has such only need to stop the control or disable the drives. They don't need to kill power completely.

But for sake of couple of £££ then I'd fit Home switches. In fact if had to lose one or other then I'd have Home switches before Limits if as they are far more useful and you can use Soft limits if need be.!

Quote:

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Originally Posted by cropwell

It is not usual to have a Z-- switch. If the object of the Z-- limit is to stop you crashing the tool into the machine bed, you need to know the tool length, so Z-- is pointless.

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Not sure I follow you, I have to learn / watch / read more about homes in order to do so. I'll watch the links you gave me later tonight :)

Quote:

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Originally Posted by cropwell

I haven't looked in proper detail at your wiring diagram, but my first impression was that it was over-complicated. I can't understand why you are talking about 10v and 24v as the BoB input pins are 5v, any higher and you could fry the board.

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Yes sorry I meant 24V and 5V. 10V is for the spindle speed control interface.

Quote:

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Originally Posted by JAZZCNC

Now personaly I don't have problem with running Limits straight to inputs provided the input can accept 24V to lessen chances of noise. Lots of BOB's are 5V only so this why relay is used so can still run 24v thru the long path to switches but keep the 5v signal line short and lessen chances of false triggers etc.

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Yes, this is why I use a relay for my limit switches. My BOB can't take in 24V.


For now, I've wired all six switches together in series, and the limits now work fine. So does the override switch and buzzer. I can't work the process of getting off a triggered switch no problem. But I'm missing homes. I could share the job on the same switches, but the relay implies some risky delay (are miliseconds really that risk JAZZ ? That's where I'm not too sure...). I'll order three more switches online for the sake of completeness of the machine, but I'll use it without homes until they arrive. Now, can you tell me what kind of switches I should get ? Laser or same type of mechanical switch ?

Quote:

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Originally Posted by eurikain

I could share the job on the same switches, but the relay implies some risky delay (are miliseconds really that risk JAZZ ? That's where I'm not too sure...).

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Not case of being risky. It's case of not being repeatable. The whole point of HOME switches is to be able to repeatabily return to Fixed position every time. The random delay between when switch is triggered and time takes relay to open it's contacts to allow message to control makes repeatabilty impossible.
The delay for limits isn't so important because like you say it's milliseconds but for repeatabilty purposes that is life time plus it's random amount of time.

Quote:

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Originally Posted by eurikain

I'll order three more switches online for the sake of completeness of the machine, but I'll use it without homes until they arrive. Now, can you tell me what kind of switches I should get ? Laser or same type of mechanical switch ?

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Again because of repeatabilty you wan't slightly better switch for homes. Personally I like using inductive Proximity sensors because they are accurate and repeatable. Well more than enough for router anyway.

I use the LJ12A3-4-Z/BX proximity sensors. You can run them off 24v (10-36v) and the wiring is simple. They are Normally Open switches, so you can put as many as you like with the outputs all connected to one active low input on the BoB. They are specced as 6-36v but don't switch reliably below 10v. Brown wire is to supply +ve, Blue to GND and the Black wire switches to GND when Ferrous metal is within 4mm of the sensor head. Again I say, mount the sensor so that the metal passes by it not end on, cause it will get crushed.

Cheers,

Rob

Plus one us pensioners have to stick together:semi-twins:

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Originally Posted by Clive S

Plus one us pensioners have to stick together:semi-twins:

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Ye and you stick together in bloody sunshine while us poor buggers freeze to death..:grief:

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Originally Posted by JAZZCNC

Ye and you stick together in bloody sunshine while us poor buggers freeze to death..:grief:

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Yes Jazz, it's a lot warmer in the South of Nottingham or the Costa del Stockport than 'Oop North'......:yahoo:

The most economical way is to have one microswitch and one inductive sensor per axis fitted on the moving part. And you mount them so that they pass by their respective adjustable metal stops on both ends.
Then you wire the sensors in parallel to one BoB input (or to separate inputs if you have them, and you can home all axis simultaneously) and the microswitches in series with the e-stop. You put the limit override to bypass the microswitches loop but not your e-stop.

In normal operation you will be using only the sensors and only for homing. You will have to set in mach3 the soft limits which will prevent you to hit the limit sensors. In the case you hit the limit sensors you tick in mach3 the automatic limit override and manually back off the respective sensor. Normally the miocroswitches will never be used, only in the worst case scenario if the software is no longer responding or the motor drives are failing, etc., then hitting the microswitch will cut the power to both motors power supply and spindle.

It is better to have both switches and sensors to operate at 24V. If your BoB do not accept 24V you can either use an optocoupler with a resistor or if the BoB inputs are optoisolated you may change the value of the resistor on the board.

I noticed you have fuses on your power supplies inputs. You want to have fuses on the outputs to actually protect the power supplies for short circuit, etc. The mains will be protected with one or more circuit beakers. (Eg. one for spindle+motors PSU and one for the 5V+24V PSU)

Edit: you will also want to wire the alarm outputs from your drive through a relay to the same limits + e-stop relay loop. In this case if one drive gives an error, the other will stop as well. It is also good to have the BoB e-stop input better connected to a mach3 input. This way you can tell mach3 to stop the g-code if the motor power switches off. So you can resume your job quickly.

Quote:

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Originally Posted by JAZZCNC

It's case of not being repeatable. [...] The random delay between when switch is triggered and time takes relay to open it's contacts to allow message to control makes repeatabilty impossible.

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Get it :) Sounds obvious now :)

Quote:

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Originally Posted by cropwell

I use the LJ12A3-4-Z/BX proximity sensors. Brown wire is to supply +ve, Blue to GND and the Black wire switches to GND

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I looked up on AliExpress but not sure I get original ones... where do you get them from ? Also, If I understand well the wiring you explain and look at the documentation as well, it seems that you're connecting them as PNP type sensor and that blue connects to both 24V PSU GND pin and BOB's input terminal's GND pin ? Is it not an issue that they share they share the same GND though they are circuits operating at different voltages ? I guess GND is GND, doesn't matter the voltage ? I like to fully understand things, that's why I ask ;)

Quote:

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Originally Posted by paulus.v

You will also want to wire the alarm outputs from your drive through a relay to the same limits + e-stop relay loop. In this case if one drive gives an error, the other will stop as well.

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That's a very important thing you note here, and I will modify my circuit to take drives alarms into account, in fact, last week I made a mistake in Mach3 and while running un-regenerated toolpath and bad configuration, motors stalled, so I almost broke my X axis, because the alarm went off, but obviously was not connected to anything, so X2 kept running... To avoid that in the future I'll wire the alarm outputs as you explained, thought the limits don't belogn to the e-stop circuit. Thanks for the advice :)

Quote:

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Originally Posted by eurikain

Also, If I understand well the wiring you explain and look at the documentation as well, it seems that you're connecting them as PNP type sensor and that blue connects to both 24V PSU GND pin and BOB's input terminal's GND pin ? Is it not an issue that they share they share the same GND though they are circuits operating at different voltages ? I guess GND is GND, doesn't matter the voltage ? I like to fully understand things, that's why I ask ;)

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You may connect all your DC 0 volt (GND) lines to ground/earth. There is no problem. Sometimes it helps solve interference issue but most of the time it doesn't really matter if you have them floating or not.

What is you BoB model?

Good to know :) My BOB is the typical Chinese Mach3 5 Axis BOB: User Manual of 5Axis Breakout Board - Mach3

Your inputs have common ground. You can use only PNP sensors. You may use 24V if you wire the input through a resistor of a calculated value. There is no info of the inputs voltage in the manual, but you could find out by reading the resistor values and/or optocoupler model.

I think all the inputs are 5V. How would I wire the resistor (I mean, I know it's a simple wiring diagram), but how do you actually wire it. Is there any kind of "terminal resistor" ?

Quote:

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Originally Posted by eurikain

I think all the inputs are 5V. How would I wire the resistor (I mean, I know it's a simple wiring diagram), but how do you actually wire it. Is there any kind of "terminal resistor" ?

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I saw only once a special resistor socket to be inserted in terminal block. And there are terminal blocks with resistors, diodes, electronics fitted inside.

The simple way is to solder the resistor to the wire end. The third method is not recommended unless you solder the input wires together.

http://i285.photobucket.com/albums/l...pswrqku5fz.jpg

http://i285.photobucket.com/albums/l...psnodaddfl.jpg

http://i285.photobucket.com/albums/l...pspcii0zxv.jpg

Quote:

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Originally Posted by JAZZCNC

No Don't use any relay for Home switches just connect direct to the Input pin or pins. The Relay cause a delay and makes homing unrelaible.

You can share one Input for all Home switches provided you use the correct switch type and connection.

If your wanting to share the Switch for both Home and Limits then you can't using the Relay approach for the above reason.

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How about using solid state relay? It doesnt have moving parts so no delay or it is very very tiny?

Išsiųsta naudojantis SM-G900F Tapatalk 4 Lt

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Originally Posted by valdis034

How about using solid state relay? It doesnt have moving parts so no delay or it is very very tiny?

Išsiųsta naudojantis SM-G900F Tapatalk 4 Lt

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Better but still not recommended or required. STR's also tend to fail in the on state which isn't good either.

So the best option is to use resistor and take 24v straight to bob?

Išsiųsta naudojantis SM-G900F Tapatalk 4 Lt

Quote:

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Originally Posted by paulus.v

Your inputs have common ground. You can use only PNP sensors. You may use 24V if you wire the input through a resistor of a calculated value. There is no info of the inputs voltage in the manual, but you could find out by reading the resistor values and/or optocoupler model.

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The LJ12A3-4-Z/BX sensors I use with this board are NPN - the output of the sensor goes to GND when triggered - which is what you want. The board has pull-up resistors so that the untriggered state is strapped to 5v. You don't need resistors as the 24v power to the sensor is limited in current to 2.4mA and in voltage by an internal zener diode in the switching circuit.

These sensors have been designed to make connection simple and to have wide application, why do people then have to make things complicated. If you complicate you introduce the possibility of design faults and unreliability.

I lose the will to live every time someone mentions a relay in a homes circuit.

For Pete's sake, there is plenty of info and advice on t'Interweb. Do a bit of searching online before you regurgitate the same old questions.

Happy bloody christmas !!!!

Rob