Centroid Community CNC Support Forum

Just finishing a retrofit on a Redsail 6090 router
Have built a compete new control box as the original was shoebox sized
the prox sensors are nc npn sensors which i was surprised ( OMCH LJ12A3-4-z/BX)
Have tried to wire them in series but the voltage drop between sensors is massive
24v supply output drops to 11v ,9v,.4v over 3 sensors in series ( holds it voltage 24v if they are not in series)
grounds are connected together , sensor output is connected to input of next
Anyone else found this with a cheap original sensor ?
Or am i doing something wrong
Geoff

When you wire proximity sensors in series, you actually create a voltage divider. That's why you're seeing the voltage drop. You have three customary options. 1). Wire each proximity sensor to its own Acorn input. 2). Install a 16X16 expansion I/O board and wire each proximity sensor to an input on the expansion board. 3). Use a method that Gary Campbell showed and wire each proximity sensor to a relay coil on a 24VDC relay board, and then wire the relay contacts in series and then to an input on the Acorn. Gary has a YouTube video that shows that concept (the video is for something different, but it shows the concept).

I would say you're doing something wrong. I've done this several times even with the cheap Chinese sensors and never had an issue. You say all the "grounds" are connected together? I always tie all the +24v brown wires together so they each receive +24 volts without a voltage drop. See the diagram below and try it this way, works every time for me.

This is an old chestnut. Although "it works for you", no manufacturer is going to condone this application. They each require a minimum supply voltage to operate correctly (typically 10V for the Omron examples), yet the supply voltage is less than 3 times that. So you can't define how it will behave when they are in series. They aren't simply a switch - they contain an electronic oscillator and detector circuit.

Far better to go for normally open (NO) switches which you can legally wire in parallel - or use a separate input for each switch. Then the behaviour is fully defined and the manufacturer would stand behind you.

Your call - but these are safety devices so the application needs to respect the manufacturer's application intent.

My experience is similar, but a note: price doesn't necessarily determine the viability. I have also seen some of the more expensive products that wouldn't work when "daisy chained".

I never use the "home/limit ALL" designations. I find more value in the discreet use of one sensor per axis, the systems messaging and direction controls available when wired in that fashion. It's nice to know which axis may be up against an axis sensor when motion is prohibited.

I fully agree that discrete inputs for each axis is "best practice" and should be utilized if possible. All I was showing is that it is possible to "daisy chain" 3 normally closed NPN switches together to wire up to one input if you are running low on inputs. I have done this on various, smaller machines and none have had any issues to date. I even added in my diagram in the upper left "this may not work for all NPN switches". I'll update it to read "use at your own risk".

If one chooses to use NO switches for homing or limits that can easily be wired in parallel to a single input that's an entire other topic for an even lengthier discussion, no?

There are probably a dozen ways to wire sensors to the Acorn and sure some are "best practice" but that may not always be "best option" for a given machine or application.

Thanks for the replies
dont think i will have enough inputs to wire them all to individually
The way you have them wired Shawn, feeds the 24v out into the 0v in , tried coudnt get that to work
looked at using relays but why make something more complicated than it needs to be.
Understand the voltage divider effect i have made with the way i wired them but was not expecting it
Have just enough outputs to run individual for the homes using the NC switches
Will swap the limits for NO switches but safety wise the NC would be a better option
( previous machine tangential knife cutter i wired the limits through a safety relay , so it would shut down if it did go OT, daisy chained micro switches)
Geoff

Skip to 1:27 in this video from Automation Direct, this is how I wire mine when needed and it works. Not sure why yours wont work per the diagram. Not all sensors are created equal I guess.

Yes, only the basic machines will require 8 or less inputs and outputs. I have had to add the ETH1616 to a number of machines, I suggest that if you wish to do it right, you will too

Hey Shawn i just realised in the video how the first is used as the trigger , dont think i was wiring it that way
spoke to my Omron rep , he said it wasn't possible , haha
Finished all but the limit switches , tt and e stop wiring
Next one Gary will have the ETH1616 - router with tool changer and dual tt
Thanks for the advice