Have you tried the darlington configuration in post #34?

Not yet. Not exactly as shown. I will later.

 

Sometimes you look at something so long you fail to see the light. Well, I feel a bit stupid, but these sensors are normally blocked, and when the valve is at full open or full closed, a slit in the trip ring unblocks it. Yes. Unblocks. The sensors are blocked all the time and activate when light is allowed through... Sigh, They have worked properly all the time, I was just using a spare sensor on my bench and tripping it with a little piece of cardboard, so I was essentially testing all of this wrong. At any rate, thanks for all of your help, and all of the support. The good thing is this went from a voltage divider to get 12V from 24V and an NPN driving an optocoupler to a more solid circuit with a proper 5V regulated circuit as shown in my last post (#59). I'm inclned to leave it as is now, as it works, but there was discussion about using some current limiting resistor betwen the Collector of the sensor and Base of the PNP transistor. What do you all think?

 

Probably don't need a resistor because of the low current output of the sensor but might be a good idea to connect a 100K between the base and the emitter of the 2N3906.

 

To be clear, the reason for the 100K resistor is to assure a clean and complete turn-off of the driver transistor. Even without light leakage, photo transistors are more leaky (have a higher off-state leakage current) than a normal transistor, and that might be enough to keep the driver transistor partially on all the time.

ak

 

Final working circuit. 100K wouldn't pass enough current to turn on Q1 & Q2.

 

100K wouldn't pass enough current to turn on Q1 & Q2.

The 100k resistors go between the transistor base and emitter to shunt any leakage current.

 

A really simpler solution will be to replace the relay with one that has bothnormally open and normally closed contacts. Ur maybe the relay in use has such but it is not shown.

 

A really simpler solution will be to replace the relay with one that has bothnormally open and normally closed contacts. Ur maybe the relay in use has such but it is not shown.

No, then the relay would be energize all the time. It actually works like I need it to.

 

No, then the relay would be energize all the time. It actually works like I need it to.

Unless the system is battery powered, why is that an issue? It certainly would be a very simple solution