sonolink

Re: Help with endstop switches wiring please
« Reply #20 on: March 04, 2021, 03:48:37 AM »
I wanted the LEDs to light when the switch is triggered (when it goes into NO), to know which switch (of the 2 on X and Y axis) was triggered. They wouldn't be lit during normal operation (with the switches in NC position).
I also have to admit that it just looked like something fancy to add to the little baby 😉
I don't know why LEDs are always so attractive 🤣

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


abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #21 on: March 08, 2021, 04:53:51 AM »
I wanted the LEDs to light when the switch is triggered (when it goes into NO), to know which switch (of the 2 on X and Y axis) was triggered. They wouldn't be lit during normal operation (with the switches in NC position).
I also have to admit that it just looked like something fancy to add to the little baby 😉
I don't know why LEDs are always so attractive 🤣

Cheers
Sono
The operation of the control board requires the switches to operate as a logic OR ((EOT is detected by opening one OR the other switch). In order to establish a logic OR, the switches must be wired in series (circuit will be open when one OR the other switch is open.
If an LED is connected, its current will be drawn from teh port's pull-up resistor. The value of said resistor is unknown (but you could deduct it by masuring the open-circuit voltage and the close-circuit current and use Thevenin's theorem); anyway whatever current pulled from ther may fool the logic and make it think it a permanent closed circuit, which would defeat the EOT detection.
It may be possible to connect sensitive photocouplers there, that would light any LED  you wish.
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 #22 on: March 08, 2021, 08:31:25 PM »
Sorry, but I'm kinda lost here.....if we forget about the LEDs, if I'm not wrong, the switches would be wired in series so that when the circuit is open by any switch the alarm is triggered, right? That could be done with any switch and any kind of switch, as long as the circuit is interrupted, correct?

So in my head I think, what if when the switch opens the circuit, it closes another one that makes an LED light up? That seems pretty basic and simple to understand to me. What am I missing that won't let me see what you are trying to explain to me?
Please bear with me...

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

abbey road d enfer

Re: Help with endstop switches wiring please
« Reply #23 on: March 09, 2021, 02:02:14 AM »
So in my head I think, what if when the switch opens the circuit, it closes another one that makes an LED light up?
That would be a dual switch, DPDT. The problem is that when one opens, the other may lag or lead, so the LED would not light exactly when EOT is reached. That is not a big issue since you want to know after the fact.
You cannot do that with a single SPDT switch, unless you have floating power supplies for the LED's like batteries. If not, the LED circuit would interfere with EOT detection. In a SPDT, which is what you have, the C pole is common to both the detection and the LED circuit.
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 #24 on: March 09, 2021, 10:01:06 AM »
I see what you mean and I understand the original makerbot switches schemo now. It's really thought for a NO config and if using more than one, to be connected in parallel...
I was focusing on the NC config because my old CNC had the limit switches wired that way....although without LEDs :)

The new CNC that I'm building is smaller than the 3040 I had, so I might just use one switch per axis (to home the machine) combined with soft limits (to avoid crashes)...or maybe I'll try the NO config...

Anyway thanks a lot for your help and your patience Abbey ;)

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


 

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