sonolink

Help with endstop switches wiring please
« on: February 24, 2021, 08:11:56 PM »
I bought these 3 pin Makerbot type endstops that have an LED for my new CNC and would like to confirm that the wiring to use 2 switches per axis in series Normally Closed is as follows:



NC triggers the Alarm and NO lights up the LED. Could someone please confirm it's correct?

Cheers
Sono
Why sleep when you can mix?
M.P.Stavrou


abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #1 on: February 24, 2021, 11:07:51 PM »
I bought these 3 pin Makerbot type endstops that have an LED for my new CNC and would like to confirm that the wiring to use 2 switches per axis in series Normally Closed is as follows:



NC triggers the Alarm and NO lights up the LED. Could someone please confirm it's correct?

Cheers
Sono
I don't think it's correct. When either switch goes on, it shorts Vcc to ground!
In order to light the LED, there is not much choice for the wiring. Vcc has to go to NC. End stop is detected by pulling S to Gnd with , which means that the C's and NO's must be wired in parallels.
But then both LED's would light when one or the other switch goes on.
I don't see how it could work.
Someone cleverer than me may find a nifty solution, though...

Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with endstop switches wiring please
« Reply #2 on: February 25, 2021, 03:44:54 AM »
I found the Makerbot switch schem:


There's 4 pin on the switch end and 3 on the board.
Does that help/change anything?

Cheers
Sono
Why sleep when you can mix?
M.P.Stavrou

abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #3 on: February 25, 2021, 05:42:40 AM »
I found the Makerbot switch schem:


There's 4 pin on the switch end and 3 on the board.
Does that help/change anything?

Cheers
Sono
That's the diagram I had consulted before sending my answer. As you can see, two pins are duplicate, so there's only three pins. You would need two separate ports on the control board with these switches..
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with endstop switches wiring please
« Reply #4 on: February 25, 2021, 09:59:34 AM »
Oh well, I guess I'll unsolder the switches from the board then. Shame, I liked the LEDs :)

Cheers
Sono
Why sleep when you can mix?
M.P.Stavrou

sonolink

Re: Help with endstop switches wiring please
« Reply #5 on: February 25, 2021, 12:20:39 PM »
I just can't give up on this like that  :)

Would this simple schematic work?



Cheers
Sono


Why sleep when you can mix?
M.P.Stavrou

abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #6 on: February 25, 2021, 12:50:32 PM »
I just can't give up on this like that  :)

Would this simple schematic work?



Cheers
Sono
Does the input "S" expect a positive level?
If there is a pull-up it may work, but you would have to rewire the LED.
If the input expects a logic zero you may rework the circuit accordingly.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with endstop switches wiring please
« Reply #7 on: February 25, 2021, 01:34:13 PM »
I measured the input at the board. There's 5v between VCC and GND and 5v between S and GND. There's 0v between VCC and S. So I guess S input expects 5v.
I appreciate your answer but I'm a bit lost with the vocabulary to be honest. I'm a learner in both electricity AND english, remember? ;)

So, what I tried to draw on that schem is that, in the NC position there's 5v constantly going around the switches back into the board (there's probably some resistor or load in it).
When one switch is triggered it goes to the NO position. The S input is no longer fed 5v triggering an alarm. The switch in that NO position allows 5v from VCC to ground the LED through its resistor and lights it up.
Where is my mistake?

Btw, what's a "pull-up"? A raise in voltage?

Thanks for your time and help :)
Sono
Why sleep when you can mix?
M.P.Stavrou

abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #8 on: February 25, 2021, 05:04:25 PM »
what's a "pull-up"? A raise in voltage?
A pull-up is a resistor from +Vcc, so the normal state is positive logic level and it expects a contact to ground.
The contrary is a pull-down.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with endstop switches wiring please
« Reply #9 on: February 25, 2021, 05:14:03 PM »
Ok :)
What about my schem? Where is my mistake?

This pull-up/pull-down is related to noise, right?

I'm thinking: if I get 5v from elsewhere on the board, I can feed the LEDs and use the switches leaving the VCC pin on the limit switches input unconnected....makes sense?

Cheers
Sono
« Last Edit: February 26, 2021, 03:14:44 AM by sonolink »
Why sleep when you can mix?
M.P.Stavrou


abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #10 on: February 26, 2021, 05:00:06 AM »
I measured the input at the board. There's 5v between VCC and GND and 5v between S and GND. There's 0v between VCC and S.
That means there's a pull-up, which generally indicates that the expected trigger is a logis zero.

Quote
So I guess S input expects 5v.
That wouldn't be my assumption.

Quote
When one switch is triggered it goes to the NO position.
Again, it's an assumption, because it depends on the mechanical construction, but let's assume it's correct.

Quote
The S input is no longer fed 5v triggering an alarm. The switch in that NO position allows 5v from VCC to ground the LED through its resistor and lights it up.
That would work if all the previous assumptions were verified.
Too many unknowns at the moment.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with endstop switches wiring please
« Reply #11 on: March 03, 2021, 03:59:43 AM »
Ok, so I've redesigned a new board like this:


How about that?
5v could it be the VCC pin I guess right?

Cheers
Sono
« Last Edit: March 03, 2021, 04:05:36 AM by sonolink »
Why sleep when you can mix?
M.P.Stavrou

abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #12 on: March 03, 2021, 09:48:13 AM »
Ok, so I've redesigned a new board like this:


How about that?
5v could it be the VCC pin I guess right?

Cheers
Sono
I don't get it. Do you have the schemo of your board?
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with endstop switches wiring please
« Reply #13 on: March 03, 2021, 10:17:09 AM »
I bought the switches on AliExpress and they won't give me a schemo of them, so I unsoldered the switches and the headers and redesigned the boards to have NC switches in series on X and Y axis. I think these switches are designed for NO operation.

Just checking with you that the board I designed is ok

Why sleep when you can mix?
M.P.Stavrou

abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #14 on: March 03, 2021, 10:40:21 AM »
I bought the switches on AliExpress and they won't give me a schemo of them, so I unsoldered the switches and the headers and redesigned the boards to have NC switches in series on X and Y axis. I think these switches are designed for NO operation.

Just checking with you that the board I designed is ok
SPDT switches are not designed for NO or NC operation. It's the circuit that defines how they are wired.
You have to understand the difference between logic inputs that require a voltage  and those that already have pull-up or pull-down resistors. And you must recognize the difference between positive and negative logic.
You need to know that; it's nor dependant on the switches. It depends on the control board.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with endstop switches wiring please
« Reply #15 on: March 03, 2021, 11:01:01 AM »
You mean that it's possible that I can't wire the switches in that way if the control board is not ready for it?

The control board is an Arduino Nano clone and on GRBL's GitHub website they suggest both wirings.

I understand your point but don't know very well what to do... :)
Why sleep when you can mix?
M.P.Stavrou

sonolink

Re: Help with endstop switches wiring please
« Reply #16 on: March 03, 2021, 11:10:02 AM »
Why sleep when you can mix?
M.P.Stavrou

abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #17 on: March 03, 2021, 06:33:32 PM »
I'm just trying to add an LED to each switch in this configuration

https://cloud.githubusercontent.com/assets/5912573/22624947/4abbfa48-eb92-11e6-8b16-5fff7d2a6a8f.png
That's a valuable oiece of info here. When the bed reaches its end of travel, it puts one or the other switch in open position. Since one end is connected to ground, that means that it opens the circuit that was otherwise shorted. It allows the input to go high, under the effect of a pull-up resistor that's built in the control card. The bad news id that you can't connect the switches to LED's. The pull-up resitor cannot deliver enough current and the LED's would probaly fool the logic levels.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

sonolink

Re: Help with endstop switches wiring please
« Reply #18 on: March 04, 2021, 01:02:27 AM »
So the only way to have LEDs there would be with a DPDT keeping the LEDs on a different circuit like say on guitar pedals.....mmm, well that's a shame :(

Anyway thanks a lot for your help Abbey ;)

Cheers
Sono
Why sleep when you can mix?
M.P.Stavrou

abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #19 on: March 04, 2021, 01:51:35 AM »
So the only way to have LEDs there would be with a DPDT keeping the LEDs on a different circuit like say on guitar pedals.....mmm, well that's a shame :(
What do you want these LED's for? When do you want them to light?
You may connect a high-efficiency LED with a high value resistor (100k) in series between NC and C; the LED would light feebly as a result of the very low current available (about 20-30 uA). It would be visible in semi-darkness.
Me, I wouldn't do that, because of the risks of improper detection;you know the consequences if you allow the bed to exceed the limits!
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

Related Topics

  Subject / Started by Replies Last post
23 Replies
12556 Views
Last post October 17, 2007, 10:03:39 PM
by Emperor Tomato Ketchup
0 Replies
1509 Views
Last post July 22, 2009, 05:57:54 PM
by charlie2012
5 Replies
1795 Views
Last post April 08, 2011, 07:00:18 AM
by r2d2
3 Replies
699 Views
Last post July 03, 2019, 11:15:49 PM
by PRR