Jann and I were cruising through cost imports one night when I saw this kick ass gong. It’s about 12″ in diameter and it sounds just like the big ass ones. I got the vision instantly…. I must make this my doorbell…. and so it was written… as confucious once said. Besides, the UPS man smoked mine when he got the button stuck so I needed a replacement. I bought the gong and started planning my doorbell. I wanted the original mallet involved some how… I think it’s kind of neat… and banging on it with other things just doesn’t sound right. I worked up a little lever scheme using a solenoid that normally drives car door locks. I spent a few hours on the mill/router and I produced a working model. There’s not much to it! Basically, the solenoid attaches at the bottom of the mallet and a pin is inserted through the mallet about 1″ above. When the solenoid is energized it pulls the base of the mallet inward creating a torque about the pin. I could have easily wired this up to the doorbell and let any jackass just bang the hell out of my gong…. but I decided not to give that jackass that satisfaction. So, I rummaged through a bunch of old circuits I have piling up around here and scrounged a PIC16F84. I wired this up to a 5 volt reg and a darlington transistor. Then I wrote a bit of firmware to debounce the button press, time the strike (amount of time the solenoid is energized), and then apply a re-arm timer. This will give the best sound (using a strike timer) as well as prevent someone from going buck wild on the gong. Finally, I had to upgrade the xfmr for the doorbell. The solenoid draws nearly 4 amps!