[dazp1976]

Hi,
if running at 24V then even a 2V-3V saturation voltage is no issue. If the same combination is presented as an input to 5V logic then yes its an issue.

Craig

Thanks Craig.
I'm still going to bench test it first.

[TeeTomTerrific]

I think I've come up with an idea for mine.
I've added a wiring diagram. Brief description:
So, entire stop circuit is NC. When estop opens/active the red light on tower lights up.
Limits:
3 limit switches in series on - end of axis tied into estop.
3 switches on + side of axis for homing wired individually.
Homing switches act as trigger for estop via opto module but then can't home without causing stop so...

Homing:
Override NO self release push button added to stop circuit, closes estop when HELD in and lights tower orange as warning via opto. Can now home without triggering e stop, if homing overtravels just release button and it opens/activates estop because switches will be lit from overtravel.
Notice push button has to be physically held while homing for it to work.

Servo spindle:
Estop tied to servo enable. Servo enable on manual button. If not enabled estop is active so MC cannot work. When enabled, estop is off and tower is green light for ready.
If servo disables itself it activates estop.
Stop also disrupts servo main power via contactor.

Other things still need to be added as I go no doubt.

See what you guys think, and mention any tweeks if you think it's crap!.

dazp1976, being the novice that I am I'm not sure I understand completely what you are doing here. I want to do a similar placement proximity NC switches that you have described, but you lose me with the rest of the description. Are the control Optos on the UB1 board? I have trouble looking at your drawing and understanding which items are on the control board, which items are the Servo drives and what other separate circuits are. I'm not sure how your home/limit override works and why it is NO. Can you do a more detailed description of your plan?

[dazp1976]

dazp1976, being the novice that I am I'm not sure I understand completely what you are doing here. I want to do a similar placement proximity NC switches that you have described, but you lose me with the rest of the description. Are the control Optos on the UB1 board? I have trouble looking at your drawing and understanding which items are on the control board, which items are the Servo drives and what other separate circuits are. I'm not sure how your home/limit override works and why it is NO. Can you do a more detailed description of your plan?

It's not working as expected just yet.
Work in progress.
1. Yes to "control" optos at the diagram bottom would be the MB1 inputs.
2. Because the limit switches are NC the entire stop circuit needs to follow suit. The reason the override switch is NO is because that if it was NC you would have 2 permanent circuits to ground. This would mean that if one was opened the other would still keep the entire thing closed making estop useless.
One needs to be off and one needs to be on (no/nc).

Normal mode: sensors activate estop via relays when limits reached.
Overridden mode: sensors bypass limit relays and don't trigger estop allowing the same switch to be used for homing.

Override button needing to be physically held in while homing, if MC overtravels, immediate button release triggers stop (quick reaction safety reasons).

Something like that.
Need to get it working properly first.


Easier, you could disable estop circuit for homing procedure but in this scenario, if it crashes you can't stop it.

[mactec54]

It's not working as expected just yet.
Work in progress.
1. Yes to "control" optos at the diagram bottom would be the MB1 inputs.
2. Because the limit switches are NC the entire stop circuit needs to follow suit. The reason the override switch is NO is because that if it was NC you would have 2 permanent circuits to ground. This would mean that if one was opened the other would still keep the entire thing closed making estop useless.
One needs to be off and one needs to be on (no/nc).

Normal mode: sensors activate estop via relays when limits reached.
Overridden mode: sensors bypass limit relays and don't trigger estop allowing the same switch to be used for homing.

Override button needing to be physically held in while homing, if MC overtravels, immediate button release triggers stop (quick reaction safety reasons).

Something like that.
Need to get it working properly first.


Easier, you could disable estop circuit for homing procedure but in this scenario, if it crashes you can't stop it.

That is a terrible circuit design you have come up with.

If it crashes like you say and can't stop it, and you are using servo drives that have a Fault output, you should be using this Fault circuit, for the Servo Drives and the VFD Drive if you have one, the Servo Drive will Fault if you have a crash as it will reach overload and Fault

[TeeTomTerrific]

That is a terrible circuit design you have come up with.

If it crashes like you say and can't stop it, and you are using servo drives that have a Fault output, you should be using this Fault circuit, for the Servo Drives and the VFD Drive if you have one, the Servo Drive will Fault if you have a crash as it will reach overload and Fault

mactec54, this may be why I was having such a hard time understanding the logic behind needing to manually hold down a button during homing. I'm mentally trying to reconcile the video you posted at the top of the previous page with dazp1976's design. It seems overly complicated, and like you are suggesting with the axis moving beyond the sensors and becoming a crash the damage will be done, but at least the drive fault should shut down the servos, or any drive fault should trip a magnetic power circuit to shut them down.

[dazp1976]

That is a terrible circuit design you have come up with.

If it crashes like you say and can't stop it, and you are using servo drives that have a Fault output, you should be using this Fault circuit, for the Servo Drives and the VFD Drive if you have one, the Servo Drive will Fault if you have a crash as it will reach overload and Fault

The point is: If it goes to crash,
You immediately release the push button you're holding in, thus engage the main circuit, and the stop will immediately trigger.
That was the point.
How would you rig it?. That's where I would like your input.
I would be homing at around 20% velocity.

I can't see how you would home if stop button is in-line with the switches, it'll just shut down every time.

I'd need another 3 separate switches..


Instead of just slating it, you could show me an alternative design.

[TeeTomTerrific]

The point is: If it goes to crash,
You immediately release the push button you're holding in, thus engage the main circuit, and the stop will immediately trigger.
That was the point.
How would you rig it?. That's where I would like your input.
I would be homing at around 20% velocity.

I can't see how you would home if stop button is in-line with the switches, it'll just shut down every time.

I'd need another 3 separate switches..


Instead of just slating it, you could show me an alternative design.

Go watch the video on the top of page 12. UCCNC knows the switch is both Home and a Limit switch because you tell it it is. If you aren't homing then it treats it as a limit switch. I am unsure how the other 3 limit switches need to be wired into the controller yet. Possibly in series with the Home Limit switches but maybe in parallel through the e-stop. That is the question I would like an answer to. Perhaps mactec54 has an answer for how that should work.

[dazp1976]

Go watch the video on the top of page 12. UCCNC knows the switch is both Home and a Limit switch because you tell it it is.

That means the switches are still only software reliant, no physical estop connection can be added to that setup. That's the point I'm making.


Will do some more reading.
As for switching:

NO switches get wired in parallel.
NC switches get wired in series.

That's generic, if you do it the other way round- one switch can't see what the other is doing and has no effect on the circuit when individually triggered.
I at least know that much..... Lol!

This wiring diagram is about right if you ignore the relays top left and take estop direct to ground. (avoiding my bypass).
The optos below the mains relays is a secondary module for mainly servo controls.
The controller optos at the bottom.




Apologies on quality. Camera not great with it.

[joeavaerage]

Hi,
is there any reason not to have separate home and limit switches?

I have six limit switches (three axis machine) each on their own input. A limit switch event causes an Estop, no ifs, no buts, an Estop. Mach knows which limit triggered as each is
on it own input, no guessing required.

I have three home switches about 3mm 'inside' the limits, each on their own input. Mach can uniquely identify which switch triggered, and there is no confusion about it EVER being a limit.

If you have a modern motion control board with plenty of inputs why bother trying to combine them?

Craig

[dazp1976]

Go watch the video on the top of page 12. UCCNC knows the switch is both Home and a Limit switch because you tell it it is. If you aren't homing then it treats it as a limit switch.

That's still only software reliant. No physical estop can be added to that setup, it would just shut down while homing.
That's the point I'm making.

All I'm technically doing with mine is:
Temporary disabling hardware stop to rely on software only.
Software can now home switches without hardware disruption.
Once homing complete, enable hardware stop again.
Now switches act as hardware stop.
That's basically it.


If I simply disable estop in the software then there's zero protection.

[dazp1976]

Hi,
is there any reason not to have separate home and limit switches?
I have six limit switches (three axis machine) each on their own input. A limit switch event causes an Estop, no ifs, no buts, an Estop. Mach knows which limit triggered as each is
on it own input, no guessing required.
I have three home switches about 3mm 'inside' the limits, each on their own input. Mach can uniquely identify which switch triggered, and there is no confusion about it EVER being a limit.
If you have a modern motion control board with plenty of inputs why bother trying to combine them?
Craig

Simply put, MC is not really big enough.
Inputs is not a problem. I have 48 available.

[dazp1976]

Go watch the video on the top of page 12. UCCNC knows the switch is both Home and a Limit switch because you tell it it is. If you aren't homing then it treats it as a limit switch. I am unsure how the other 3 limit switches need to be wired into the controller yet. Possibly in series with the Home Limit switches but maybe in parallel through the e-stop. That is the question I would like an answer to. Perhaps mactec54 has an answer for how that should work.

I will likely end up using UCCNC to do its thing with the home switches. I just wanted to figure a way of having hardware stop attached to those 3 as well.

My overall original config was having the - axis ends on hardware and + ends controlled via software anyway.


To put it another way, I remember one time we had a new guillotine machine come in at work, all singing and dancing automation. Stop circuits were mostly software controlled. The laser safety barrier blipped a few times and still cut while the op was inside the barrier. Heidelberg never figured a problem with it but, it didn't stick around long!.
You can't trust software alone!.

[mactec54]

mactec54, this may be why I was having such a hard time understanding the logic behind needing to manually hold down a button during homing. I'm mentally trying to reconcile the video you posted at the top of the previous page with dazp1976's design. It seems overly complicated, and like you are suggesting with the axis moving beyond the sensors and becoming a crash the damage will be done, but at least the drive fault should shut down the servos, or any drive fault should trip a magnetic power circuit to shut them down.

As in the Video is all you need, simple is best, extra button to push would get old fast if you are using a router Gantry type machine, the next step would be to use a Safety Lock out Relay, but that gets expensive and not needed at the Hobby level, servos will fault with the first sign of overload, ( this you can set in the Drive) faster than you could move your hand from a button, machines in general don't crash once they have been configured correctly, soft limits prevent crashes into end stops if they are setup correctly

[mactec54]

That's still only software reliant. No physical estop can be added to that setup, it would just shut down while homing.
That's the point I'm making.

All I'm technically doing with mine is:
Temporary disabling hardware stop to rely on software only.
Software can now home switches without hardware disruption.
Once homing complete, enable hardware stop again.
Now switches act as hardware stop.
That's basically it.


If I simply disable estop in the software then there's zero protection.

No if the EStop is not connected the machine should not be able to run, the only way you can normally bypass the EStop is with a Jumper, this is a bad Breakout Board design if you can run the machine without the EStop connected in the circuit

[dazp1976]

No if the EStop is not connected the machine should not be able to run, the only way you can normally bypass the EStop is with a Jumper, this is a bad Breakout Board design if you can run the machine without the EStop connected in the circuit

Still connected. Just bypassing the 3 relays that are triggered by the home switches secondary line. Everything else is fully operational.

Will just settle for the soft limit, software stop, home detection on those 3 and hard stop with the 3 switches on the minus ends.

[dazp1976]

No if the EStop is not connected the machine should not be able to run, the only way you can normally bypass the EStop is with a Jumper, this is a bad Breakout Board design if you can run the machine without the EStop connected in the circuit

Stupid schoolboy error.
Neglected to take into account the amount of current relay and contactor coils use. Connected my basic isolator control modules up in series for NC stop circuit on the bench, however, when they triggered the contactor it burnt a resistor due to current.
They have just enough for the ralays.
I don't want to spend too much on this and I do already have a 16chnl plc amplifier board 5A per O I got ages ago. But the way it is set up it's no good for NC. Only NO.
So I figure I have 3 options.
1. Use the modules with the relays to trigger contractors which seem borderline for my little control modules, or.
2. Connect the modules to the amplifier npn and use the amplifier to power all relays / contractors and poss selonoids in future. Or.
3. Bin it all off as experience and get some new control modules with more guts.

Don't really want to do 3 if I can help it.
Just seems 1 thing controlling another thing to control another thing etc is a bit much of a chain.

Ah well. That's how we learn :withstupi

[mactec54]

Stupid schoolboy error.
Neglected to take into account the amount of current relay and contactor coils use. Connected my basic isolator control modules up in series for NC stop circuit on the bench, however, when they triggered the contactor it burnt a resistor due to current.
They have just enough for the ralays.
I don't want to spend too much on this and I do already have a 16chnl plc amplifier board 5A per O I got ages ago. But the way it is set up it's no good for NC. Only NO.
So I figure I have 3 options.
1. Use the modules with the relays to trigger contractors which seem borderline for my little control modules, or.
2. Connect the modules to the amplifier npn and use the amplifier to power all relays / contractors and poss selonoids in future. Or.
3. Bin it all off as experience and get some new control modules with more guts.

Don't really want to do 3 if I can help it.
Just seems 1 thing controlling another thing to control another thing etc is a bit much of a chain.

Ah well. That's how we learn :withstupi

You need a Snubber with any Relay Coil / Contactor Coil Switching or something in the circuit will burn up. some Relays have built in Snubber's you would have to check the specs of what you are using, some SSR have built in Snubbers

[dazp1976]

You need a Snubber with any Relay Coil / Contactor Coil Switching or something in the circuit will burn up. some Relays have built in Snubber's you would have to check the specs of what you are using, some SSR have built in Snubbers

Will look into it.
Question.
If say I'm going +/- +/- +/- +/- in series across a load of opto inputs to switch them all on at the same time. Would I benifit from a snubber across each +/- input to keep power maintained?.
Or am I being dumb again?.

[mactec54]

Will look into it.
Question.
If say I'm going +/- +/- +/- +/- in series across a load of opto inputs to switch them all on at the same time. Would I benifit from a snubber across each +/- input to keep power maintained?.
Or am I being dumb again?.

Only the device switching like a Relay requires it. No one is dumb, unless they make the same mistake twice, and then it's only a dumb mistake which often can be corrected

[dazp1976]

No if the EStop is not connected the machine should not be able to run, the only way you can normally bypass the EStop is with a Jumper, this is a bad Breakout Board design if you can run the machine without the EStop connected in the circuit

I've been bench testing circuit designs.
This version is fully working as intended.
Technically it turns out it'll work fine just using the amplifier but the stop logic modules lights make it 'pretty' lol. Any kind of fault and limit trigger activates stop, and the circuit is expandable. Anything you think I would need adding, feel free for constructive criticism.

The orange tower warning light comes on when a home switch is active. With the little switch in the O Position they activate estop, with it in the I position it only works with the software. Estop still functions in both positions, if homing faults the orange will be lit too long so you know to hit stop button.