Making a door chime

[petehall347]

Re: Making a door chime

[eccerr0r]

Re: Making a door chime

<sarcasm>One...microcontroller... </sarcasm>

[Dannyx]

Re: Making a door chime

Right, I was actually wondering whether they made DUAL 555s...I just realized that battery life would be a big problem with that countdown timer I had in mind, since it "leaks" VCC to GND via the discharge pin when "disabled", so that's no good at all....will have to rethink it. That's another thing I needed to mention: battery life if important since I can't run any wires up to that door.

[goontron]

Re: Making a door chime

[Dannyx]

Good day folks. This may seem like something totally stupid and pointless, but I want to make one of those chimes which emit a fairly loud sound when someone opens the door to let me know someone has walked in Of course you can just buy one of these, but that's beside the point.

I'm thinking of the humble 555 again and sure enough, I found something which is fairly close: THIS. I'd like it to beep 5-6 times in rapid succession at a high pitch (2000Hz or so) then stop (how these chimes typically work). To achieve this, I may need TWO 555s: one to generate the ringing (which is illustrated in the article) and another to handle the 1-2 second countdown in which the thing is allowed to beep, then cut its power so to say. A N/O reed switch in alarm systems will detect the door's closure/opening: when the door is closed, so is the switch and the circuit is disabled. When the door opens, so does the reed switch, which triggers a fast sequence of beeps then stops - that would be the operating principle.

I HAVE built a 555 countdown timer for another project so I know that works, but I was wondering if someone had any better ideas to cut down the part count even more. 2 555s seem a bit overkill.