Doing some clean up around the house I found an old wireless doorbell but not the remote to activate it. I started to toss this in the trash. Rather then throw it away I decided to turn it into an alert box for connection to an Arduino or maybe my PC to alert me when something needed my attention. Here is the result, an awesome sounding bell and a very bright LED, driven by two power MOSFETS. Just about anything can drive the signals to make a bell or flash a bright red LED.
The enamel coated, transformer wires come from the bell ringing solenoids. Only one is used. The way this doorbell was setup, one coil would ring both bells and one would ring just the longer bell. I intended to remove the shorter bell so I only connected the coil for the long bell.
A power N-Channel MOSFET controlled from a digital output drives the gate to turn on the FET which pulls down on the coil to ring the bell.
A second FET pulls down the return on a high brightness LED. You can easily see the LED though the plastic cover. You might see this LED from the Moon if it were not covered. This is a 1 Watt LED I got some time ago, it is one of the few parts that was not scrounged here.
The MOSFETS were new as well. I tried to use one I had scrounged but it required too much gate to source voltage and I ended up blowing it.
Here is the finished box. The wires coming out of the side are currently connected to my Umbuntu box. I have some custom software that I’m working on. it rings the bell or flashes the LED. I’m thinking of connecting this to IRC to let me know when someone mentions my nick (uCHobby). But I need to learn a but more about Linux software development first. It could also be driven by an Arduino. I might wire this up to my front panel project which will use an Arduino to control switches, lights, meters etc…