What’s the Difference between 2-way, 3-way and 4-way solenoids?
First, what is a solenoid actually?
In a simple sense, a solenoid is really just a valve. It allows gas (or water) to pass through the valve when the valve is opened. In fact, a 2-way solenoid is just like the valve for your garden hose. It can be closed or open. The solenoid valve is generally opened by giving it electricity.
ON = Air goes through
OFF = No air goes through
But, sometimes, you need the valve to do more than just being open or closed. That’s when the 3-way and 4-way (sometimes called 5-way) solenoids come in handy.
Let’s say you want to use a solenoid to shoot a blast of air at someone. A 2-way valve is perfect for that. The valve has pressure behind it, and it patiently waits to receive electricity. Then BAM! The air flies through.
But, now let’s pretend you want to use a solenoid to inflate an airbag instead. What happens after the airbag is inflated? You close the solenoid, but the airbag will remain inflated because there is nowhere for the air to go. In this case, you need an “escape valve” for the air to exit from the airbag.
Enter the 3-way solenoid. A 3-way solenoid is just like a 2-way solenoid, but with the addition of an escape valve to let the air out when the solenoid is closed. This is the extra hole, or “port” to be more specific, that you see on a 3-way solenoid valve. Usually, we put a brass colored muffler in this hole to keep out debris, muffle the noise of air escaping or to control the rate at which air escapes.
ON = Air goes through
OFF = Excess pressure shoots out muffler, and no new air goes through the solenoid
Ok, now let’s say you want to use a solenoid to make a pneumatic cylinder shoot out, and then pull itself back in. If you use a 2-way solenoid, the cylinder will shoot out, but there’s no way to pull it back in.
If you use a 3-way solenoid, the cylinder will shoot out, but it will not pull itself back in.
Behold, the 4-way solenoid! A 4-way solenoid has 1 port for the air to enter the solenoid from your air compressor, 2 ports for shooting out air, and 2 ports for mufflers to control the “escape” air.
OFF = air goes out port #1, and excess pressure from port #2 escapes through the muffler
ON = air goes out air port #2, and excess pressure from port #1 escapes through the muffler
The neat thing about the 4-way solenoid is that each of the two air ports can be hooked into the two inputs on a 2-way cylinder.
In the OFF position, air will flow into the top input of the cylinder – keeping the cylinder pulled back tight.
In the ON position, air will flow into the bottom input of the cylinder – pushing the rod of the cylinder out as far as it will go.