I was working on a refrigerator that the light inside the refrigerator was not working. After doing a lot of searching, I finally found a reed switch at the top of the door that signals when the door is open/closed.
I unplugged the reed switch and touched the Two prongs on the reed switch plug together “closing the circuit” and voila, the light worked as if I had activated the switch. So, I thought maybe the reed switch was bad. I swapped it with the freezer door one. The reed switch worked in the freezer, and the freezer one did not work in the refrigerator. So, both reed switches are good.
Next, and question is coming. I decided to try activating the reed switch by directly placing a pieces of metal and different magnets (the kind of magnets that you place on the front of refrigerator doors) to the reed switch. And nothing I could find would activate either reed switch. Why?!
In normal operation, the reed switch is located behind a thick piece of plastic inside the door. Apparently there is some kind of material inside the door that is activating the reed switch when the door closes. I was able to move the reed switch around manually and fine the material and got it working. I adjusted the reed switch a little to get it in a better position to be able to activate, and it is working as of right now. However, I am worried it isn’t going to work reliably.
My question is why couldn’t I activate the reed switch with a refrigerator magnet? The other reed switches I have dealt with before would activate this way. Is this reed switch less sensitive? Are there different types that work with a certain pole of the magnet?
It just didn’t make sense to me. The model number on the reed switch was 590140-917.
I assume these are the type that have a rubber/plastic backing to them? It may be because of the way this type of fridge magnet is made that it won't activate a reed switch.
I mean that same thing you would get if you had bothered to Google for "bar magnet". We do not want to have to spoon feed you, so if someone here mentions a term you don't understand, please try to do a little research before you ask about it.
The link does not work. When you post a link please check it works.
Point taken, but you probably could have given me the answer with as much effort as you put in to that response. In addition, we would have been on the same page as a google search for “regular bar magnet” produces a wide variety of results.
It wasn’t a link it was supposed to be an image. Hence, the .jpeg file extension. Maybe it wasn’t my fault that it didn’t post? Maybe not.
If it is a bother for you to answer questions, why post?
Indeed. I could have given you a fish instead of encouraging you to learn how to fish.
I try to give the benefit of the doubt and assume people want to learn to fish.
The first result I get is
Bar magnets look like regular rectangular magnets but they are magnetised in a specific way. To be a ‘bar’ magnet, the magnet must have the north pole on one end and the south pole on the other, magnetised down their length. This means that they are stronger on each end where the pole faces are located. This is different to rectangular magnets which are ordinarily magnetised so that their north and south poles are on the larger, flat faces and magnetised through their thickness.
Bar magnets are used when maximum strength is required from a small pole area. They are also commonly used to activate reed switches in proximity and counting applications. And, of course we must not forget the traditional alnico bar magnets, which are usually painted to identify the north and south poles and have been used in classrooms for decades!
To operate a reed switch, the direction of the magnetic field has to be along the axis of the reed switch.
See the the diagram below (taken from here).
Those magnets that are used to stick on to fridge doors are going to be a north pole on one side and a south pole on the other, so that when you present one face of the magnet to the reed switch you are not applying a magnetic field in the correct orientation for it to operate.
I experimented with some of the magnets on my fridge earlier, when @neketege88 asked the question. I found something interesting. They seem to be "striped"! By which I mean stripes of North pole separated by stripes of South pole (as seen from the back surface) or maybe stripes of no particular magnetic orientation. I found this by sliding two identical magnets over each other, and in only one orientation, I could feel the "ridges" where the stripes of opposite poles in the two magnets attracted each other strongly, separated by gaps where the same poles repelled each other very slightly, or at least didn't attract.
I didn’t know asking another person or member of a forum that exists to share knowledge was not “learning” or “fishing”. Geez, guess I was wrong when I ask my grandpa to help me learn to tie that clinch knot when we were out on the lake. Guess I should have gone to the library and checked out a book….
Interesting. So, if I understand you correctly, if I were to have taken the magnet that was on the fridge and flipped it over, this orientation would have worked?
This is interesting as well. This doesn’t seem like the magnets you had worked as @JohnLincoln described above. Although, I could be misunderstanding. Please forgive me if I am.
@PaulRB, btw, I really appreciate this response. It was very interesting to read, and I think it will help me better understand the topic…. Thanks!
