Welcome, Foolish Mortals, to the ...
Introduction
When you ring my doorbell, instead of hearing a "ding-dong", you hear "Welcome, Foolish Mortals...". To "haunt" my doorbell took about $35 of parts from Radio Shack and around an hour of assembly time (or about one-tenth the time it took me to document how I did it ;-)). It required making only the most minor and easily reversible changes to the exiting doorbell circuit, and the haunting can be easily "exorcised" out when needed...
This document describes how I built and installed the haunted doorbell. If you want to replicate the design, feel free, but I assume that you are knowledgeable enough about electronics not to break anything or cause a hazard :-)
Ingredients
I apologize I don't have Radio Shack part numbers for most of the parts -- but hopefully the photos later on will help. Besides, by now, the part numbers will have changed or they will have newer versions of similar things...
| Part | Usage |
| 1 Digital Voice Recorder (Radio Shack #276-1326) | This is the heart of the of the unit; it records and plays back the Ghost Host's message. |
| 4 AA Batteries | To power the above |
| 1 Mini stereo jack | To hook the speakers up to the recorder |
| 1 Set cheap, unpowered speakers | To be placed outside |
| 1 Small perf board | To assemble doorbell interface |
| 2 9 Volt SPDT relays | To drive existing doorbell and voice recorder |
| 2 Mini mono plugs and 2 Mini mono jacks | To connect / disconnect from doorbell circuit |
| 9 Volt battery clip | To hook battery up to doorbell interface |
| 9 Volt battery | To power doorbell interface |
| 1 Small project box | To stick everything in |
Design Overview
The design consists essentially of two halves. The first part is designed to be inserted into the existing doorbell circuit which allows it to continue to function as before but also has the doorbell button trigger the playback of the message. The second part is the actual circuitry that records and plays back the message.
The part that interfaces with the existing doorbell is entirely hand built, while the part that records and plays back the message is completely pre-built!
The Before Picture...
Your typical doorbell circuit is the model of simplicity. Normal (and lethal!) 120 volt AC power comes in from the main and goes through a transformer to become non-lethal 12 volt AC power. One side of the power goes to a bell/buzzer/box-that-plays-chimes, while the other side goes to a switch by your front door. When someone presses the switch button, it completes the circuit and power flows to the bell/buzzer/what-have-you to make a noise. More sophisticated doorbells (e.g., those that play "Lavender Blue") may have more complicated circuitry, but for this project we can safely assume they're all the same (unless you have a fancy wireless doorbell, in which case give up now...).
One of the unpleasant things about the above circuit is that, while the 12 volts AC is pretty much harmless to you and I, it's deadly to the electronics of the recorder/playback circuit. We need to isolate the doorbell from the playback, and that's the task of the "doorbell replicator", which is built out of relays.
The After Picture ...
When the Haunted Doorbell is installed, the old doorbell continues to function as before. But now, the doorbell button also triggers playback on the recorder/playback circuit...
Building the Haunted Doorbell
Building the Haunted Doorbell consists of three main steps:
- Building the Doorbell Replicator
- Interfacing the Doorbell Replicator to the Playback Module
- Installing the Haunted Doorbell
Step 1: Building the Doorbell Replicator
The doorbell replicator is very, very simple, consisting of three main parts and a couple of connectors:
We run 9 volts from the battery out to the doorbell button, and when the button is pressed it supplies power to the two relays in the Replicator. Note that this is in many ways almost the same as a doorbell circuit -- just with relays instead of a bell!
One of the relays runs back to the original doorbell circuit. In essence, the relay is acting as a surrogate doorbell button. The other relay runs over to the recorder/playback module and triggers playback.
I assembled the whole circuit on a small piece of perf-board using point to point wiring. There is nothing fancy done or needed:
The blue boxes are, of course, the relays. The two connectors in the lower left run to the doorbell switch (red) and the doorbell circuit (black). Instead of using both male or both female connectors on the replicator. This allows me to easily remove the Haunted Doorbell and (on the other side) reconnect the doorbell switch to the doorbell circuit to restore "normal" operations (should playful spooks interrupt the Haunted Doorbell's operation). I used female connectors when the connector sourced a live voltage (so that loose male connectors could never short anything), but that's just an extra flourish.
You'll notice the red wire in the top-middle leading away from the board and going nowhere: that connects to the modified playback module....
Step 2: Interface the Recorder/Playback Module
The Digital Voice Recorder come assembled from Radio Shack, but needs a few simple modifications. Out of the box, the unit (with the not-included batteries installed) looks like this:
The white push button on the left controls the recording of a message, while the green button triggers the playback. We're going to remove the green button and hook it up to the doorbell replicator. The silver blob towards the top is the microphone. Just below it is a LED which turns on during recording and playback. The speaker and battery pack are obvious.
If you play with it as-is (which, of course, you'll do) you'll notice that the speaker is really bad. Actually, the speaker isn't so bad, it just needs to be mounted in/on something. If you cut the bottom out of a Dixie Cup and use it like a megaphone for the speaker, the sound improves a lot.
But not enough. So the first thing I did was cut off the speaker and attach a stereo mini jack in its place so I could hook it up to real speakers:
Now, when I hook it up to Walkman-style speakers, it works much, much better. The next step is to hook the unit up to the doorbell replicator, which I did by removing the green button and hooking the two wires up to the relay. When that's done, the complete, assembled circuit Haunted Doorbell looks like this:
The final step is to cram it into a box:
(This is a prototype, remember?)
And then put the lid on and attach the speakers:
(You'll notice that I have hooked it up to a pair of $8 Radio Shack "moisture resistant" speakers: Only the best!)
Now, record your greeting and get ready to install the Haunted Doorbell!
Step 3: Installation
This step is going to be the most vague, since it depends entirely on how your home is set up. You'll need to figure out the following:
- Where are you going to put the box, itself?
- Where are you going to put the speakers (or speaker, it doesn't matter -- the output is mono)?
- Where are you going to tap into the doorbell circuit?
- How are you going to run wiring between the speaker(s), the box, and the doorbell circuit?
In my case, I was lucky. There's a protected shelf above my front door on the outside, and I was able to put the box and the speakers right there. I ran two pair of wires (unobtrusively) right to the doorbell button, and hooked one pair up to the button itself and hooked the second pair up to the wires going back to the doorbell chimes. This way, to remove the Haunted Doorbell entirely, I just have to reconnect the doorbell circuit to the doorbell button and pull out the two pair of wires.
You probably won't have it this easy...
You want the Greeting Too?
OK, you want to hear the Ghost Host intone "Welcome Foolish Mortals..."? Buy a Disney park CD ... I recorded it onto the doorbell by ... gasp ... holding the microphone of the recorder/playback unit up to my PC's speaker! Cheap! Effective! Easy!
And that's it! Have fun! Remember, the Haunted Doorbell has many practical uses too. I just can't think of many at the moment...
Comments? Suggestions? Write me at cmcguinness@mindspring.com!
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Copyright 1999 Charles McGuinness. All Rights Reserved.