PMDX Forum
General Category => Cables, connectors, switches, contactors, sensors and other items => Topic started by: robert.beal on July 25, 2016, 01:37:47 AM
-
I have aquired several pnp contrinex sensors 100$ each (DW-AD-623-04) the current leakage is =<.1mA when i hook up the sensor to the pmdx-126 board the light is on really dim when the switch is triggered the light gets bright on the board but in either case the signal to mach 3 is always on. How do i fix this problem. i heard npn sensor can have this this problem but no one has mentioned anything about pnp sensors. Any advise would be appreciated. Thanks!
DW-AD-623-04
Application Type Standard
Rated operating distance sn 1.5 mm
Mounting Embeddable
Hysteresis ≤ 20 % sr (10 % typ.)
Repeat accuracy norm ≤ 5 % sr
Supply voltage range UB 10 ? 30 VDC
Permissible ripple content ≤ 20 % UB
Output current ≤ 200 mA
Voltage drop ≤ 2 V
No-load supply current ≤ 10 mA
Off-state current ≤ 0.1 mA
Switching frequency ≤ 3000 Hz
LED Built-in
Ambient temperature range TA -25 ... +70 ?C
Ambient temperature range TA US -13 ? +158 ?F
Temperature drift of sr ≤ 10 %
Short-circuit protection built-in
Polarity reversal protection Built-in
Power on reset Built-in
Degree of protection IP 67
Housing material Stainless-steel V2A
Connection Cable
-
I found the data sheet here:
http://www.contrinex.com/xml/productSheet.aspx?src=ps_DW-AD-623-04&langage=English&typeFolder=IND
Looking at the PDF, the PNP sensor has an internal 47K res from the output to gnd. The PMDX-126 presumes that the PNP sensor will be either "open circuit" or pulled to +24V. The sensor's internal 47K resistor to GND appears to be fooling the PMDX-126's input circuit to make it think there is an NPN sensor (or mechanical switch) that is "active".
Are you powering your sensors from an external 24V DC power supply?
I can see two ways to work around this:
(1) Add an external diode between the sensor's black wire and the PMDX-126's input terminal. The cathode of the diode (the end with the stripe on it) should go on the PMDX-126 side. This will prevent the sensor's internal resistor from sinking current from the PMDX-126 and falsely triggering the input. This can be any 1N4001, 1N4002 or 1N4148 style small signal or switching diode.
**OR**
(2) Add a resistor from the PMDX-126's input terminal to the "+5V" terminal on J11 or J12. The resistor could be a 2.2K ohm, 4.7K Ohm or maybe even 10K ohm. This *should* keep the sensor's pull-down resistor from drawing enough current to trigger the PMDX-126's input circuit. But please note that I haven't tested this solution yet (I'm working from home this morning).
I'll see if Steve has any other suggestions later today.
Bob
-
I added the external diode and it worked great. (No false triggers)
Thanks again for the help!
-
Glad to hear it!
Bob