Calling any reed switch experts.

[ukracer]

I have a couple of very old fox micron bite alarms and I need to get them into action again.

They are extremely old and fox don't want to know. BUT I think it's just a reed switch problem but I don't know how to identify it.
One works fine the other is very intermittent. Any ideas peeps
@ajlelectronics is most likely my best best I guess?

 

[skotl]

Do you mean you don't know how to identify what is the reed switch? Must admit that I thought they were always glass with filament contacts, however I might be wrong

Maybe it has a hall-effect sensor instead?

 

[skotl]

Oh wait - on closer inspection, I take it this is the reed switch?

In which case, I'd expect you can replace it with pretty much any switch

 

[Bullet2012]

Ok so pleas excuse my ignorance, but , what is a reed switch ?

 

[MattF]

Ok so pleas excuse my ignorance, but , what is a reed switch ?

A nearby magnetic force closes the switch.

 

[Bullet2012]

A nearby magnetic force closes the switch.

Ahh, so nothing to do with reeds then. I had visions of a war between thatchers and computerites disputing who owned the riverbanks.
appreciate the now obvious explanation.

 

[Misterg]

so nothing to do with reeds then

The contacts are thin strips of magnetisable metal (reeds) that are flexible enough to touch when they are put in a magnetic field.

In the pictures above, the one on the left is broken, the one on the right isn't.

A replacement just needs to have the right length glass envelope.

 

[ukracer]

Oh wait - on closer inspection, I take it this is the reed switch?

View attachment 302751

In which case, I'd expect you can replace it with pretty much any switch

Yep. It's glass is broken so it's random in operation (mostly does not work)
Double checked by shorting the two sides and I get a constant noise. So everything is working as it should except the reed switch.

Looking on eBay it seems a bog standard cheap part and as it's only operating a buzzer and led every time one of two magnets go past it I don't even think amps with come into it.

Got one on the way for 99p. Lol

 

[skotl]

Yep. It's glass is broken so it's random in operation (mostly does not work)
Double checked by shorting the two sides and I get a constant noise. So everything is working as it should except the reed switch.

Looking on eBay it seems a bog standard cheap part and as it's only operating a buzzer and led every time one of two magnets go past it I don't even think amps with come into it.

Got one on the way for 99p. Lol

Yep - they're not the most complex of devices!

 

[skotl]

Ok so pleas excuse my ignorance, but , what is a reed switch ?

Matt is spot on in his description above. Reed switches are extremely simple, don't need any power or complex circuitry but as demonstrated above can be very fragile.

Hall effect sensors are more commonly used nowadays, but there are definitely pros and cons to both.

This is a good article on when you might use one over another: How to Decide Between a Reed Switch or a Hall Switch (thomasnet.com)

 

[DAPPH]

The contacts are thin strips of magnetisable metal (reeds) that are flexible enough to touch when they are put in a magnetic field.

In the pictures above, the one on the left is broken, the one on the right isn't.

A replacement just needs to have the right length glass envelope.

They are either normally open contacts ( " N.O ." "
or
Normally closed contacts ( N.C. ) make sure you've got the right one . They can also be current rated to about 15 amps or more for some industrial switches , yours will be a very low switching current .


They usually die because one of the reed leaves gets metal fatigue and cracks eventually rendering it useless .

 

[Alan Reynolds]

They are either normally open contacts ( " N.O ." "
or
Normally closed contacts ( N.C. ) make sure you've got the right one . They can also be current rated to about 15 amps or more for some industrial switches , yours will be a very low switching current .


They usually die because one of the reed leaves gets metal fatigue and cracks eventually rendering it useless .

Glad you mentioned the NC and NO. They also have different force responses to the magnets

 

[ukracer]

Glad you mentioned the NC and NO. They also have different force responses to the magnets

This one must be NO as it has a spinner the line runs over and turns it. As it turns it closes the contact. Then the arm 90° has no magnet and it stops bleeping. Then 180° another magnet closes it again causing a constant bleeping that varies with the speed the fish has run off with the bait.