# School Bell



## T-Man (May 16, 2008)

Any ideas on how to slow down a 6 inch school bell. It uses 24 volts AC. 20 does work.


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## tjcruiser (Jan 10, 2010)

Slow down?!?!

Why? Having a tough time keeping up with the school kids these days?!? 



What dictates its speed? Is it simply power frequency ... 60 Hz? Or is it some sort of a capacitor that loads / discharges ???

Looks like a challenging "homework" assignment!

TJ


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## gunrunnerjohn (Nov 10, 2010)

Add weight to the ringer arm as far out as possible, the mass should slow down the oscillation. 

How slow do you want it to go?


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## Big Ed (Jun 16, 2009)

Your trying to slow it down to sound like a crossing bell?

Reduce the electromagnetic field somehow?
Maybe attach a heavy spring to it somehow ( epoxy)? to slow it down?

I thought you might find this site interesting.
http://matt.zont.org/signals/crossings/xngworks/xngworks.html

A copy and paste from there,
Most mechanical crossing bells work basically the same way as a standard electric bell, such as a school bell or fire bell. That is, an electromagnet forces the clapper to the gong and in so doing disconnects its own electrical supply internally through a set of contacts, causing the armature to fall back until the contacts close and the cycle repeats. There are about 200 distinct strikes per minute. The crossing bell rings more slowly than a school bell or fire bell because of the relatively large mass of the parts involved, and also perhaps some hysteresis in the contacts. Yet it works on the same basic principle. 
However, there is such a thing as a motor-driven bell.


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## gunrunnerjohn (Nov 10, 2010)

That's exactly what I was driving at, more mass makes it slower. It may be necessary to actually add a circuit to do the energizing of the coil if it can't be slowed down sufficiently.


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## T-Man (May 16, 2008)

I have a starting point now. My first idea was to stiffen the spring across the magnets. Adding weight sounds easier. For speed I want to hear separate dings. One a second maybe. I must have 200 a minute no doubt so I a looking at cutting it to a half.

The only other thought I had was a capacitive discharge system like a switch, more complicated but just a thought.

Thanks for the tips, Nice site Ed a good find.:thumbsup:


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## gunrunnerjohn (Nov 10, 2010)

Hmm... Cutting 200 in half is 100, one a second is 60. Sounds like you want a third. 

I'm not sure you can add enough weight or springs to slow it down that much.


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## kursplat (Dec 8, 2010)

trade the school bell for a school kid with a hammer...


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