Does the TS know anything about either sensor? How many wires it had? What connections did it have? Did it have a power supply connection? or a connection to a common???
Did the TS remove the previous sensor, or was it removed and discarded by another? (I have had to deal with that situation.)
It is entirely appropriate to request additional information from a client requesting assistance, unless you are the one who designed the machine being serviced. In addi tion, given that the client in this case has not provided the additional information it seems likely that they will not be able to implement a simple transistor circuit to effect the logic reversal. That could be a problem.

 

Is there a way I can add a comparator with a adjustable set point to the pnp converter circuit #38? I don't want any Hysteresis.
Thanks in advance.

Jeff.M

 

i would say why reinvent the wheel? there are ready products just for this:
https://www.phoenixcontact.com/en-us/products/solid-state-relay-module-dek-trinv-2964319

 

Based on the responses in posts #24 and #31, the TS is trying to help a third party of unknown qualifications. Certainly a sensor with the correct operation mode is available, but not from the same source as the third party has selected. Unfortunately we have no hint as to the ability or skill level of the person actually doing the replacement, who may not be the TS.
Revising a PLC program is not simple as it requires, as a minimum, the software for programming that model of PLC. That software can be HORRIBLY EXPENSIVE it it is an Allen Bradley PLC, or free with some of the Automation Direct PLC products. Without the correct software access is impossible.

 

Is there a way I can add a comparator with a adjustable set point to the pnp converter circuit #38? I don't want any Hysteresis.
Thanks in advance.
Jeff.M

Did you try the modified PNP version in post #40?

 

circuit in post 25 and 40 are example of what the TS needs (or the off-the shelf solution like in post 43). one in post 40 would ensure proper operation in case of leakage current. there should be a 10V Zenner at the input too, to avoid false trigger.
since there is not knowing the experience level of the users trying to make the change, the question is if the circuit was put together correctly which is why i would propose considering off-the-shelf solutions.

PLC inputs draw little current (couple of mA). usually the low limit is about 9-10V and high is 12-15V.

choosing wrong sensor is unfortunately not that rare as many do not read or understand the documentation. modifying PLC software is a possibility but not always welcome, and depending on situation may be impossible (could be locked by manufacturer).

it is still not known what type of sensor or QD is used, many are M12 and for that there are also inline converters. they are super easy to install since no tool is needed, but may be bulky and not practical in some cases, for example if mounted of the endeffector of the robot.

 

Members,
I have the problem solved. I added a small resistor from the base to the emitter and that allowed me
to control the switching level for the inverter.
Thanks again for helping me with the inverter circuit.

Jeff M.

 

I added a small resistor from the base to the emitter

Yes, which is what I showed in post #40. Glad to here it's finally working.

 

good. that would suggest that there is a leakage current in the sensor output so inverting transistor was not completely turning off

 

Yes, which is what I showed in post #40. Glad to here it's finally working.

Yes refer to post #40 but I used a 1k value resistor.