I need to deactivate a Limit Switch

[mesden]

I need to deactivate a Limit Switch that looks kind of like this:

http://www.omron.com.au/product_info/V/v_limit_switch.jpg

There's two wires that go into it but only one of them comes out. I don't know what the other one does. One of the wires is connected to one of the prongs which easily comes off, I just don't know what to do to deactivate the Limit Switch without deactivating the whole series of electronics. Any ideas?

[Brian_Beal]

What to you mean by deactivating?  What do you mean by go into and come out of?  If you want to bypass the limit switch, connect the wire that is on the common terminal to the wire that is on the N.C. terminal.  I am assuming that the limit is wired to open when the switch is hit.  If there are 3 wire, then it is likely that the switch is also serving another purpose, perhaps it is being used by another device.

[mesden]

There are two wires, one of the wires is on one of the prongs, but the other wire isn't able to move. It's kind of stuck in place on the side of the Switch.

[AnalogKid2DigitalMan]

Cut the blue wire! Or was it the green? (Just kidding)

We really need to know more about your setup. It looks like the switches are of single-pole double-throw (SPDT) style. This means that one of the wires goes to a terminal called common (COM). The other wire must go to the normally closed (NC) OR the normally open (NO) terminal. You need to tell us which one it is.

Now, presuming that the limit switch lever is pressed down when the stage travel mechanism is supposed to stop at it's limit-

If the wire was connected to NO terminal, leaving this wire disconnected will 'deactivate' the function of the limit switch.

If connected to the NC, then to 'deactive' the limit switch, you must connect this wire to the other wired connected to the COM terminal

I do not know why you want to deactivate the function of this switch. It is there for a purpose to tell the electronics controlling the motor to stop motion. You risk damaging the motor, motor driver, stage mechanism, or even a person nearby depending on what this all is  without it.

Does this make any sense to you?

-AK2DM

[mesden]

It's a limit switch for a power wheelchair. When it tilts past a certain point, the Limit Switch goes active and prevents the Chair from moving. Yes I realize it's due to a safety factor, but I'd still like to know how this is deactivated.

There are two wires that goto the Limit Switch. One is stuck in place on the side of the Switch, while the other is removable, placed on one of the prongs. I removed it from one prong and placed it on the other, but it didn't remove the Limit Switch's function entirely. It's still there, but now if you tilt the chair so you're sitting upright, then tilt it again so it begins to tilt back, the Limit Switch will automatically lock the Chair from driving immediately. (I know how to fix it from doing that, but I'm still trying to see if it's possible to take out the function of the Limit Switch entirely.)

[Brian_Beal]

Either just disconnect the wire or short the 2 wires toghether.  One of those options will disable(ignore) the limit switch.

[jamrite]

Mesden,

There are many kinds of limit switches and it is very difficult for anyone to very accurately answer your question without more details.

Having said that, I will attempt to explain the principle of the most basic limit switch. The hope is that understanding this will help you answer your own question (or serve as future reference).

Principle:

Most limit switches will have a common terminal (terminal 1) which under normal circumstances (when the switch is not pressed) will be connected to terminal 2. Since terminal 2 is usually connected to terminal 1, it is called "Normally Closed" (NC). Terminal 3 is usually NOT connected to terminal 1 and hence is called "Normally Open" (NO). Now, when the switch is pressed, terminal 1 is connected to terminal 3 (for as long as the switch is pressed).

Most limit switches have NC and NO marked on the side. You said that a wire is "stuck in place on the side of the Switch"; this might be the common terminal (terminal 1).

Now, you have to figure out which of the two prongs is NC or NO. The procedure to deactivate the switch will depend on whether the wire was originally connected to NC or NO.

If the wire was originally connected to NC then you short it with the wire on the side. If it was originally connected to NO then you leave them unconnected. However, if by chance, both prongs had a different wire on them originally, then there is some control logic when the switch is open AND when it is closed. In this case, you really need the switch and should not be deactivating it.

Hope that helps!

Jaidev Amrite

Applications Engineer,

National Instruments

[jamrite]

I had posted a picture with my reply. Apparently not everyone can see it so I am attaching it here.