Sunday, October 17, 2010

School Bell

Having several irons in the fire has never stopped me from opening the door when opportunity comes knocking. Ok, so this school bell didn't exactly "find" me so much as I was out at one of my usual haunts Treasure Mart looking for neat treasures when I came across IT.

It was labeled "School Bell - $8.00" and that was it. It rattled when I shook it, which turned out to be a mounting screw, surplus to requirement, left inside. Despite the mysterious rattle and the rusted condition of the bell it was too good of a find to pass up.


As you can see here it is labeled "The Autocall Co.". It also says [0].22 Amps, 24 Watts and 115-60. The last designation I take to mean 115 volts at 60 Hertz aka standard US AC voltage/frequency.


Immediately after getting home I opened it up to discover the bell's simple design. A spring dampened plunger in an AC solenoid. Each half of that 60Hz sine wave causing the plunger to move to and fro; ringing out that familiar and much awaited signal that class was over. This time, however, there would be no "Pete, please see me after class.". Shenanigans will abound.




The bell came with two 14 Ga. wires, one stranded the other solid, attached to the solenoid. Testing the bell by jamming these wires into an outlet controlled by a wall switch proved that the bell works. Not a surprising revelation after the visual inspection. However, needless to say, jamming bare wires into an outlet is not a long term solution to powering this bell and they were removed in favor of a two prong plug which you can see in the above pictures.

This thing really is quite loud. The microphone on my camera cannot pick up the audio too well until the amplitude falls within range.



Now, I have several ideas on what I will do with this bell in the future but I imagine nothing just yet. I think the application will present itself when the time is right. Perhaps an alarm to alert you the refrigerator door has been left open for too long. An alarm clock? Maybe use a PIR sensor to trigger the bell for a couple seconds anytime it "sees" a person enter a room. Or it could ring each time an email comes into my inbox. Certainly this serves as another reminder that an inductive vehicle detector loop is desirable in everyone's driveway. And of course with Halloween just around the corner it could be used to just plain scare the living daylights out of some poor unsuspecting soul. Let me know in the comment section what you would do with a school bell of your own.

A brief word on safety. Although this is called a school bell I believe they are also used in fire alarm systems. If nothing else I believe some people might interpret the sound to mean "DANGER". With this in mind I only activate the bell where those that can hear it are aware that the sound is not intended to signal any type of emergency condition. I encourage you to consider this possibility if you happen to come across such an item to play with too.
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