@ -63,6 +63,27 @@ Before realizing this error, I breadboarded two op amps, (ref: https://electroni
Next, I will breadboard the triple 5 with the LM324 (which may be optional) and use that. I will throw in an Arduino to switch the triple 5 on/off via the RST pin. This will allow for some adjustment of tone.\footnote{I could just use the tone() function on the Uno, and have a transistor handle the output, but the goal of this project was to lean more towards the analog.} Future improvements would be to get some way of removing the Arduino from the project. I would need a solution that will adjust how often the RST pin is switched, for some short period of time while the door magnet switch is active.
I might end up just using tone, if the 555 doesn't sound good.
\section{Door Magnet Reed Sensor}
I tried buying one from mouser,digikey but they are all small. Seems the standard is 28mm by 10mm or so. I didn't realize it until I purchased it, but it looks quite a bit smaller than I am used to. Not acceptable.
I spent some time looking at all the options. I was unable to find the bigger size. Even the imports from Sparkfun and Adafruit were small. There was a nice screw terminal omrom option but it was \$30. I opted for ebay where there were some used, brand name, sensors in the US. I found some for about \$5 each, including magnet AND the sensor (on mouser/digikey, you often have to get them separately).
\subsection{Buzzer or Bell}
I thought about a buzzer. Like, a ringer from a telephone. I didn't find them on mouser/digikey, but I did see a lot of piezo buzzers. Need to look again. Even better would be a bell, but that requires an actuator or a motor. I don't want to deal with moving parts, it will be more likely to break. Let's put that idea aside for another day.
Still, I like the idea of a bell, and an actuator to ring it...
I tried one on ebay. If that doesn't work there is this one: