2 Attachment(s)
MACH3 AKZ250 BOB WITH NPN NO PROXIMITY SENSORS
Hello Gents
I have a problem, regarding the wiring of the NPN Normally Open proximity sensors and there seems to be some confusion about this, especially when I refer to the schematic, which the user manual supplies. I will attach two pics of the info, which I have.
The MACH3 manual shows that the settings, must be set as ACTIVE LOW, when using NPN type proximity sensors.
The sensors have 3 wires.
BROWN, BLUE AND BLACK.,
This is a test, which I did this evening:
I connected my 24 V DC power supply to the sensor. BROWN wire to BROWN on sensor and BLUE to BLUE wire on sensor. Measured the voltage there and got 24 V. When I placed a screw driver in front of the sensor, the LED came on. This is all Normal.
A search on YouTube revealed that a resistor was used and attached to the BLACK wire. This wire is the SIGNAL wire and was plugged into the port on the BOB. When the sensor was activated, the voltage dropped to around 0 Volts.
Further Testing:
I placed a RESISTOR between the BLUE and BLACK wires and the voltage was shown as 5,8 V with the SENSOR NOT ACTIVATED. When I activated the resistor, the voltage dropped to 0,7 V. This proves the theory of the video clip on YouTube.
The wiring diagram on the NPN sensor, shows a resistor (load) between the BLACK and BROWN wires. The BLUE wire seems to go to the GND on the BOB (I could be wrong)?
Please look at the two attached pics and look how the AKZ 250`s user manual, shows the wiring for this BOB?
If I put a RESISTOR between the BLUE and BROWN wires, I get 23,6 V and when I activate the sensor, the voltage drops to 0,7 V.
I just want to know the correct way of how to connect these NPN type NORMALLY OPEN sensors to this BOB.
Regards
Craig
Re: MACH3 AKZ250 BOB WITH NPN NO PROXIMITY SENSORS
Hello Gents
I sorted this problem out and its working properly now.
Regards
Craig
1 Attachment(s)
Re: MACH3 AKZ250 BOB WITH NPN NO PROXIMITY SENSORS
having had a quick look at the AKZ250 manual
this is what you have when the sensors NPN open collector output is connected to one of the AKZ250 inputs
Attachment 405656
I have calculated the additional resistance required to limit the AKZ250 input current to 7mA when you connect it to a +24V supply
the pull up resistor I calculated is 2700 ohms
the value given in the manual is 3300 ohms this will reduce the current that will flow into the AKZ250 input
and will reduce the voltage you will measure at the AKZ250 input terminal to about 4.64V
when the sensor is triggered and its NPN output transistor short circuits the AKZ250 input to ground
the voltage at the input terminal will depend on saturation voltage of the NPN transistor -
the 0.7V you have measured is what I would expect
as the sensor has a normally open NPN open collector outputs that only sinks current to GND and can not supply current from the 24V supply
it is safe to connect sensors in parallel
the AKZ250 will only sense when the first sensor is triggered
I expect you will need to set the sensor as active low in mach 3
as the AKZ250 input is high (+5v ) until the sensor is triggered and the AKZ250 input goes low (0.7V)
John
Re: MACH3 AKZ250 BOB WITH NPN NO PROXIMITY SENSORS
Quote:
Originally Posted by
john-100
having had a quick look at the AKZ250 manual
this is what you have when the sensors NPN open collector output is connected to one of the AKZ250 inputs
https://www.cnczone.com/forums/attac...d=405656&stc=1
I have calculated the additional resistance required to limit the AKZ250 input current to 7mA when you connect it to a +24V supply
the pull up resistor I calculated is 2700 ohms
the value given in the manual is 3300 ohms this will reduce the current that will flow into the AKZ250 input
and will reduce the voltage you will measure at the AKZ250 input terminal to about 4.64V
when the sensor is triggered and its NPN output transistor short circuits the AKZ250 input to ground
the voltage at the input terminal will depend on saturation voltage of the NPN transistor -
the 0.7V you have measured is what I would expect
as the sensor has a normally open NPN open collector outputs that only sinks current to GND and can not supply current from the 24V supply
it is safe to connect sensors in parallel
the AKZ250 will only sense when the first sensor is triggered
I expect you will need to set the sensor as active low in mach 3
as the AKZ250 input is high (+5v ) until the sensor is triggered and the AKZ250 input goes low (0.7V)
John
Hello John
Thank you for your reply.
I used a resistor on the BLACK signal wire, to the input pin on the AKZ250 and set the sensor to ACTIVE LOW. It was just a little confusing to see how the user manual had shown the wiring of the sensor. I think that this did confuse a few people before?
Regards
Craig