Normally open, normally closed, common info for solenoid valve

[ihaniff]

Hi Katherine/Dartmouth team,

I am an engineer working on setting up something similar for tree shrew research at Vanderbilt. It always helps to have projects like yours to reference, especially ones with such robust documentation! I came across it on the OpenBehavior page if you are curious.

I reached Chapter 6 where you discuss solenoid valves and expressed uncertainty about the terminology used in the diagram for it, so I wanted to chip in and help.

For your solenoid valve, you have three ports. One is labelled common. This one will connect to either of the other two valves; which one depends on whether or not the solenoid is energized. The port is "common" to the other two. If I understand it correctly for your particular model, the normally open valve is "normally" connected to the common port. Normal[ly] means when the solenoid is not energized. The normally closed valve is not connected to the common port when this is the case since only one port can connect with the common at a time.

Then you energize the solenoid and the connections switch. It is not the normal situation anymore. Now the "normally closed" port is connected to common, and "normally open" port isn't connected to anything.

This would explain why the reward fluid leaks out of normally open port when the solenoid isn't energized. It will suck up the fluid in the tubing connected to the common port and spit it out of the normally open port, unless you plug it up with caps.

To summarize:

Solenoid = not energized
Common connected to normally open
Normally closed not connected

Solenoid = energized
Common connected to normally closed
Normally open not connect

Going into the weeds a bit, I think the normally open port is the "exhaust port" and the normally closed port is the "pressure port" if we use more frequently used terminology for valves. The common port would be the "cylinder port", conveniently starting with the same letter. The full description of this type of solenoid (LHDA0531115H) is 3/2-way monostable NC, with NC meaning that the solenoid is normally closed-type and the cylinder/common is connected to exhaust/normally open when not energized. Very confusing terminology, I agree... I digress. Here's a schematic for this type of solenoid from Tameson, another manufacturer:

Of course they use P, A, and R as the port designations. For them P stands for pressure/inlet, A stands for cylinder/outlet, and R stands for exhaust.

Anyways, I hope this helps! Thanks again and please continue to do great work! Eventually, I will get my act together and also share what I do with others on Github. It would be my way of meaningfully contributing to the broader research community.

Isaac