Retrofit My Build Looking at Switching from Mach4 to Centroid System

[Onawa220]

Optical limits/homing switch help.

this is the diagram the designer of my previous controller drew for me so I couldn't screw it up too bad and it worked perfectly.

I already have 24v running out to the machine that I then tap the red wire/anode for all switches into. I have the 1W resistors on each optical switch as well.

I have the white wires/collectors connected to the inputs 1-6 on the AcornSIX. On my old controller board I could run 5v, 24v or 0v to the inputs. I had those inputs connected to 24V

Green and black wires are all connected together and on my old board it had terminals marked 0V that I connected those to.

I have 24v coming from the H16 connector and connected to COM 1-4 & COM 5-8. I have the green/black combined wires connected to the H16 COM connection on the AcornSIX.

I have tried all combinations of where to connect the cathode side I cannot get a signal on the AcornSIX. The only thing I have not tired yet is removing the resistor or trying 5v out to the machine side and use that to connect the optical switches.

And I just connected a switch without a resistor on it and still no joy. I'm missing something really obvious here aren't I? I've checked and I am getting power to the switches.

[centroid467]

You definitely need the resistor to limit current through the integral LED so please do not remove them. Powering the LED side without the resistor could damage the LED.

If you wired the resistors to 24V like in the old setup, it should work with the cathode terminals wired to H16 COM/logic GND. However, it seems like you had everything correct like this:

* Black/Cathode should go to H16 COM
* Red/Anode should be connected to an individual resistor per switch and the other side of the resistors go to a 24V power supply. This could be H16 +24V pins or even COM 1-4 or COM 5-8
* White/Collector goes to the IN1-IN6 pins
* Green/Emitter should go to H16 COM

If it did not work when wired like this, then I would look for faulty wiring, bad connections, damage to the switches, etc.

[Onawa220]

You definitely need the resistor to limit current through the integral LED so please do not remove them. Powering the LED side without the resistor could damage the LED.

If you wired the resistors to 24V like in the old setup, it should work with the cathode terminals wired to H16 COM/logic GND. However, it seems like you had everything correct like this:

* Black/Cathode should go to H16 COM
* Red/Anode should be connected to an individual resistor per switch and the other side of the resistors go to a 24V power supply. This could be H16 +24V pins or even COM 1-4 or COM 5-8
* White/Collector goes to the IN1-IN6 pins
* Green/Emitter should go to H16 COM

If it did not work when wired like this, then I would look for faulty wiring, bad connections, damage to the switches, etc.

I took a bit of a break to clear my mind then got back to work and got my servos working and now I'm back to the limit switched.

I took a brand new optical switch with a resistor on the red wire.
I connected the red wire directly to the 24v V+ terminal
I connected the black and green directly to the 24v V- terminal (I have a dedicated 24v power supply for my laser so I wasn't connecting to the 24v & 5v PS that came with the AcornSIX).
I connected the white to an input. The LED on the AcornSix stayed red and blocking the optical slot did not change the state of the LED.

I then experimented and swapped the white input and connected it to V- and the green & black to the input on the AcornSix. The LED on the AcornSix was now green but blocking the slot did not trigger a change in the LED.

I did not have CNC12 running and the input configured but that shouldn't matter for triggering the LED right?

What am I doing wrong?

[centroid467]

A picture would be very valuable here.

* Did you connect the red wire or the free leg of the resistor to the +24V? If the resistor is not in series to limit current to the optical sensor's transmitter LED then the sensor could be damaged. Regardless, the red AcornSix input LED means that the optical switch output was not conducting which would imply that the slot is blocked or the internal LED is not illuminated.

* The second configuration you tried could give different results depending on whether the V- terminals of the two power supplies are connected or not. If they are connected, then I would have expected it to read as open circuit due to the transmitter LED not having any real current through it. If the supplies are floating with respect to each other then I could see a way for some current to go through the sensor's transmitter LED and then possibly conduct enough to trip the AcornSix input. However, this is not how any of these devices should be used and I would not expect it to be reliable.

CNC12 does not have to be running nor does the PLC have to be configured for the input LEDs on the AcornSix to show the input state.

[Onawa220]

A picture would be very valuable here.

* Did you connect the red wire or the free leg of the resistor to the +24V? If the resistor is not in series to limit current to the optical sensor's transmitter LED then the sensor could be damaged. Regardless, the red AcornSix input LED means that the optical switch output was not conducting which would imply that the slot is blocked or the internal LED is not illuminated.

* The second configuration you tried could give different results depending on whether the V- terminals of the two power supplies are connected or not. If they are connected, then I would have expected it to read as open circuit due to the transmitter LED not having any real current through it. If the supplies are floating with respect to each other then I could see a way for some current to go through the sensor's transmitter LED and then possibly conduct enough to trip the AcornSix input. However, this is not how any of these devices should be used and I would not expect it to be reliable.

CNC12 does not have to be running nor does the PLC have to be configured for the input LEDs on the AcornSix to show the input state.

I have the resistors over on the CNC. 24v comes into the distribution block and then each red wire for the optical switch is soldered to one end of the resistor and the free end of the resistor is connected to a terminal of the distribution block.

Nothing has changed on that end and on the board side I have the same free ends that were connected to the Mach4 board.

I will try connecting them directly to the connections on the AcornSIX and see if that solves it.

Would it be better to use the 5v inputs and power them this way? Would I still need a resistor in that case?

[Onawa220]

As I'm still making my brain work with electricity and understand why things are working I did some check with my multimeter.

On the other side of the resistor (resistor connected to 24v the other end connecter to the red wire of the switch) I'm getting 1.331v out. This was obviously fine on my ESS Mach4 board because the switches worked. Is this not allowing enough power through?

I also checked each input on H4 & H5. Since I have the 24v coming around from the H16 connection and jumpered from Com 1-4, 5-8 13-16 each terminal has 24v at it when I use my meter on them. I also have the red wire of the switch connected to a 24v source. Should I be sending power on the red & white/input wire?

Every time I THINK I'm understanding this thing I get more confused and frustrated and feel even dumber.

[centroid467]

Thank you for the pictures. I believe I see 2.2k ohm resistors which would give you about 11 mA through the switch's LED emitter (red wire to black wire). If you measure from the red wire to the black wire, I would expect to see somewhere between 1.2 and 1.4 volts according to the datasheet for the emitter (TT electronics OP240). So, that is probably fine. I did notice that the emitter is not really rated for reverse operation (2V maximum rating!) so it is not a good idea to put the red wire to signal ground and the black to a positive voltage.


The white wire goes to the collector of the output phototransistor which should be pulled up to 24V through a resistor. That pull up resistor is built into your AcornSix's inputs already so the white wire should go straight to the input. Connecting the output side of this device in reverse could also damage it - the Emitter to Collector breakdown voltage is 5V (OP550 datasheet).

I don't know what is going wrong here because the wiring should have been right and the voltages make sense. I'm going to get my hands on these and try for myself but I would suggest doing what user silver2row did and use other kinds of switches.

[Onawa220]

Thank you for the pictures. I believe I see 2.2k ohm resistors which would give you about 11 mA through the switch's LED emitter (red wire to black wire). If you measure from the red wire to the black wire, I would expect to see somewhere between 1.2 and 1.4 volts according to the datasheet for the emitter (TT electronics OP240). So, that is probably fine. I did notice that the emitter is not really rated for reverse operation (2V maximum rating!) so it is not a good idea to put the red wire to signal ground and the black to a positive voltage.


The white wire goes to the collector of the output phototransistor which should be pulled up to 24V through a resistor. That pull up resistor is built into your AcornSix's inputs already so the white wire should go straight to the input. Connecting the output side of this device in reverse could also damage it - the Emitter to Collector breakdown voltage is 5V (OP550 datasheet).

I don't know what is going wrong here because the wiring should have been right and the voltages make sense. I'm going to get my hands on these and try for myself but I would suggest doing what user silver2row did and use other kinds of switches.

I asked him which he went with but while I wait for him to reply which switches do you find work best without having to add resistors etc to just plain work with the AcornSix?

[centroid467]

As Shawn said under your post in silver2row's thread, pretty much any inductive NPN NC switch will just work after wiring it in correctly.

Parts we suggest for those on a budget can be found on this page: https://www.centroidcnc.com/centroid_di ... _gear.html

With that type of sensor, all you need is to put the brown wires to +24V DC, the black wires to the inputs, and the blue wires to the AcornSix input power supply common (V-) terminal.

[suntravel]

As Shawn said under your post in silver2row's thread, pretty much any inductive NPN NC switch will just work after wiring it in correctly.

Parts we suggest for those on a budget can be found on this page: https://www.centroidcnc.com/centroid_di ... _gear.html

With that type of sensor, all you need is to put the brown wires to +24V DC, the black wires to the inputs, and the blue wires to the AcornSix input power supply common (V-) terminal.

Jup, these SN04-N are easy to mount, dirt cheap and precise. Do not try to invent the wheel again since you got schematics and links for components that are proved to work well

Uwe