Need help with npn n/c proxy sensor wiring!!
Hi everyone,
i am new to this forum and really need some help to connect my proxy sensors.
I have the following breakout board:
DB25-1205 ( powered from external 5v DC psu)
https://forum.linuxcnc.org/media/kun...5DB25-1205.pdf
proxy sensors are the following:
Lj12A3-2-Z/AX NPN NC 3 Wire DC 6-36v
my plan is to use a 12v external psu to power all the 3 sensors which I intended to use for homing on my 3 axis. No limit switches will be added as I have set the soft limits. The reason I am changing to proxy as the traditional mechanical switches failed few times due to vibration when I was running a bigger tool on higher speed.
my plan was to either use:
- one sensor / input
-or all 3 sensor in series to one input.
I am using pin15 for e-stop so both option could work but i would like to make it as simple as possible.
after some research i've found if all 3 connected in series I need to use diodes and resistors which is not a problem. or if I use individual pins no need according to few related post.
if anyone could help me shed some light on this would be much appreciated, thanks.
Re: Need help with npn n/c proxy sensor wiring!!
I asume by connecting in series you mean connecting the GND for sensor 1 to the output of sensor 2, the GND for sensor 2 to the output of sensor 3
If you measure the voltage on the output when this NPN NC proxy is activated, you will measure the supply voltage. This is because most of these proxy's have an internal pullup resistance. You power these proxy's using one PSU. Just make a drawing for the 3 proxy's and their pullup resisance the way you want to connect them in series. Maybe that sheds some light.
The current of sensor 1 and 2 would flow through the output of sensor 3 and the pullup current of all 3 sensors would flow through the output of sensor 3. That whould exceed the max current of sensor 3.
Proxy's aren't the same as ordinary switches and you can't connect them in series but you can connect them parallel.
If you want to use 1 input for all proxy's, you need NO proxy's connected parallel (al the outputs connected together to the input of the board).
Beware that the input on your board should handle the 12 Volt (proxy pullup currents) of all 3 proxy's simultaneously! If the board is designed for 5 Volts, you need a resistor (optocoupler) or diode (digital input).
2 Attachment(s)
Re: Need help with npn n/c proxy sensor wiring!!
with this BOB
Attachment 433116
you need to use sensors with open collector NPN outputs
I have only seen N/C PNP sensors wired in series
As you have enough inputs , I would connect 1 N/C NPN sensor to 1 input
before using a 12V supply for your sensors
check they have an open collecter with no internal pullup resistors between the output and pesitive supply
simple check just power a sensor and check the output between the negative supply and output is all ways 0V
If the output goes positive when the sensor switches off
you need to add a diode between the sensor output and BOB input -
the diodes cathode going to the sensor output
this will stop any current flowing out of the sensor and into the BOB's input
Attachment 433118
one problem with normally open sensors is the control can not detect a broken sensor or wire
John
1 Attachment(s)
Re: Need help with npn n/c proxy sensor wiring!!
If the Lj12A3-2-Z/AX NPN NC sensor has a an internal pullup resistor
connect the sensor output to the BOB input via a 1N4001 diode just to make sure its not damaged
the reverse breakdown voltage of the LED inside the BOB's opto-isolator is about 5V
with the BOB's input open circuit
if the sensor has an internal pullup resistor the cathode will be connected to +12V and anode to +5V via the
sensors pullup resistor and BOB's 330 ohm resistor
Attachment 433240
John
PS
not sure why the attachments in post 3 are not visible
1 Attachment(s)
Re: Need help with npn n/c proxy sensor wiring!!
how are you powering the BOB?
Attachment 433318
if you have jumpers JN1 & JN2 installed so the same 5V supply is connected to both
Vcc & Vdd that powers the input side of the opto-islators and
+5V & 0V that powers the PC side of the BOB
noise picked up on the proxy sensor wiring has an easier path into a PC printer port or motion controller
than it would with the jumpers removed and a second isolated 5V power supply used
just to power the Vdd & Vss terminals
that way you have galvanic isolation that's lost with the jumpers installed
John
Re: Need help with npn n/c proxy sensor wiring!!
Quote:
Originally Posted by
Jprorok
I have just checked with my multimeter, and I have about 100v AC induced between the motor housing and the cnc framework, if I ground the frame to the vfd ground terminal it drops down to 45v AC. Any thoughts how to get rid of this completely ?
Also fitted a ferrite ring magnet on all my motor wiring and limit switches but still no joy :/
After adding a layer of silicon washer and electrical tape around the proxy sensor mount the voltage reduced to 20v ac
It sounds like you have something connected to Ground that should not be , post some photo's of your wiring may be able to see what is wrong
1 Attachment(s)
Re: Need help with npn n/c proxy sensor wiring!!
one problem with a machine built from anodised aluminium parts is the aluminium oxide film will act as an electrical insulator
I have seen a few photos of Chinese machines with earth / ground wires screwed to the inside of the control box
and fail to make a connection !
you have to remove the anodised surface to make a connection to the aluminium metal underneath
check the continuity from the earth / ground terminal on the VFD to the motor cable earth / ground wire
then to the 4 pin spindle motor connector
then check the continuity from the earth / ground pin is internally connected to the motor case
it can be missing on Chinese spindle motors !
John
PS
saved from a post here on cnczone
Attachment 433718
Re: Need help with npn n/c proxy sensor wiring!!
I guess if you connect in series you mean connecting the ground of sensor 1 to the output of sensor 2, and the ground of sensor 2 to the output of sensor 3. When this NPN NC proxy is active, the power supply voltage can be measured by measuring the output voltage. Because most of these proxies have inner tensile strength, they do. In this case, I would try to use a residential proxy and it should solve the problem. This will fix the connection that shows up as an error.