It's funny how one awesome project leads to another. After showing off my Audio Memory Chest at Boston Makers (my hometown makerspace), one of the city's 2018 Artists in Residence asked me I'd be interested in building an "oral history phone booth" for him.
The basic concept: he would record oral histories with senior citizens around the city; I would put them into an old rotary payphone from the 50s. Visitors could go into the booth, dial a number on the phone, and hear one of dozens of stories.
Naturally, I was stoked. It's a project that has all of my favorite things: old stuff, audio, stories, electronics, and interactivity. FYI, I didn't originally intend to do an instructable, so the photos aren't the best, but hopefully this will give you a sense of how to do it yourself. You can still find old rotary phones for pretty cheap on ebay or antique stores—and they're a pretty cool way to hear stories.
To recreate this prototype, you'll need:
- 1 rotary phone
- 1 Arduino Pro Mini
- 1 Catalex Serial Mp3 player
- 1 Adafruit Audio Amp
- 1 2-port screw terminal
- 1 1/8" headphone plug
- 6 Crimp-on spade connectors
- 6-wire ribbon cable
- 6-pin ribbon cable headers (male and female)
- 2x 10k resistors
- wet/dry sandpaper
- Black gloss lacquer spraypaint (or the color of your choice)
Step 1: Open Payphone to Expose Inside
The phone we managed to find was an old Automatic Electric payphone. You may be able to find something similar—as long as it's a rotary phone, the brand doesn't matter. Ours looked awesome, but was pretty beat up, and definitely didn't work... which is good, because most of the innards have to be removed for this project anyway.
If you use a payphone, you'll first need to crack it open. Old 3-slot phones like these come in three main pieces—there's a metal backboard, a faceplate, and a coin vault. Most of the electronics live inside the faceplate. All three parts lock securely into each other, so you'll either need a key (which you can buy online at aptly-named oldphoneshop.com), or need to drill out a few screws on the back side to release the coin vault and internal latches. More on that here.
Once the coin vault is off, the faceplate will come off pretty easily. Lucky for us, the locks were all busted anyway, so we could open them with a small screwdriver.
Step 2: Remove Ringer and Coin Mechanism
Next, you'll need to take out all the electronics and electromechanical stuff. At the top, you'll see the coin mechanism and the ringer. Find the 3-4 big screws that hold this down, and take the whole thing out in once piece. (Most of these old phones use flathead screws to hold everything together, so you won't need anything fancy).
Next, all are connected to screw terminals, which lead to pointy metal pieces. When the faceplate is attached to the back, these push against metal reeds, connecting circuits to the hook and handset without leaving wires hanging between the two parts. Pretty neat.
Remove all the wiring from the phone and set aside or discard. We'll be re-attaching our own electronics to these parts later.
Step 3: Remove Dial Mechanism
Once you have the all the parts out of the frontplate, you'll need to take out the dial mechanism. Be careful - there are lots of specialized screws involved, and you DO NOT want to lose any of these.
First, take off the big brass screw in the center of the dial. This will let you remove the dial itself.
When that's off, turn the faceplate over. On the back, you'll see three long screws that hold the whole dial assembly onto the front of the phone. Remove these and save them - you'll need them to put it all back together. Gently pull the assembly off the front of the phone, and disconnect the wires. (On most of these old phones, the wiring is all connected with screw terminals for ease of maintenance—so it'll make disassembly a lot easier.)
Step 4: Prep Case for Painting
Once all the electronics are out and the dialer is removed, you can prep the case for repainting. I used wet-dry sandpaper (400-800 grit) to take off any rust, scratches, or other imperfections in the finish, and get things ready for painting. The smoother you can make it now, the better the final finish will be.
Be sure to use painter's masking tape to cover any chrome features or other spots you don't want covered. I put a few layers on the coin return the port and the coin slots on top of the phone, as well as some other spots I wanted to keep clear. I also removed the hook mechanism from the backboard so I could cover that with a nice black finish as well.
IMPORTANT: be sure to mask the keyholes on the locks before painting! If you don't, you may not be able to get a key into them to re-lock them.
Step 5: Paint and Buff Case
Acrylic Laquer works really well for a nice shiny finish. I layed down multiple light layers, sanded the imperfections with wet-dry sandpaper (use progressively smaller grits from 800-2000), and then buffed the finish with plastic polish. I like the Novus 7136 kit - works like a charm on both plastic and paint finishes. You can do it by hand or with a power buffer - probably easier with the latter, but be careful not to press too hard or you'll take off layers of paint.
Step 6: Connect Dialer to Screw Terminals
Once the paint has dried, we can reconnect the electronics. On the back of the dialer, connect the two dial pulse terminals (pictured above) to a pair of wires. Run them back through the front of the case, then attach them to the two connection points shown here. Re-attach the dial assembly to the front of the case (you saved those screws, right?)
Step 7: Build Wiring Harness
You'll need to connect the dial, handset, and hook to the arduino. To do that and make it simple to assemble, I created a wiring harness out of a six-wire ribbon cable. One end has screw terminal lugs; the other has a single six-pin ribbon cable connector. That end will plug into the arduino board, so the whole thing can go together without needing to hard-wire pins.
Step 8: Connect Hook Switch and Handset to Screw Terminals
On the backplate of the phone, wire one end of the hook switch to 5v, and the other the screw terminal I've identified in the photo. Likewise, make sure the handset earpiece is wired to its own two screw terminals.
Finally, attach the screw terminal ends of the wiring harness as shown in my notebook (see photo). Run the single 6-pin cable down through the top of the coin vault - that's where the arduino and other boards are going to go.
Step 9: Build Sound/Amp Boards
Here's where the electronics come in.
I used Adafruit perma proto boards, partially because because that's what I had on hand, and partially because they made wiring things a little easier than just a normal blank protoboard. They copper traces on them mimic a breadboard, so you can take advantage of 5v/ground rails, etc. Pretty nice.
Wire up the arduino, serial mp3 player, amp breakout, and 6-pin connector as shown in the schematic. Since I couldn't fit everything on one board, I just used two, and installed a ribbon cable to bridge the connections between them.
Once you've got everything in place, install it all in the coin vault of the phone (I glued in some wood scraps so I could screw down the boards first). Plug the 6-pin ribbon cable on the end of the wiring harness into the 6-pin port you made on the board. You're ready to start editing audio and tweaking your code!
Step 10: Load Audio Onto SD Card, Tweak Arduino Code
Now we'll load the audio files and sound effects for the ringer/busy signal/operator error.
First, select the audio you want to use. If you can, edit each file so they're at a uniform volume first. This is optional, but recommended. Reaper, Audacity, or another free audio editor will work.
Using an SD adaptor, open a microSD card on your computer. Download the three sound effects files I've posted here, and drag them onto the top level of the card.
Next, make a new folder on the top level of the card, and name it "01". Drag any mp3s you want to play on the phone into this folder. Rename the files so they start with sequential numbers: (001_file.mp3, 002_file.mp3, etc), then eject the card and insert it into the serial mp3 player.
Almost done! Now we tweak the Arduino code so each file has a phone number associated with it. This will make more sense when you read the notes/rollover text on the the images here.
- Set the variable "totalNumFiles" to whatever your grand total is (minus the sound effect files). In this case, I had 30 in all.
- Give the files nicknames using the "define" function. I used each interviewee's name and a file number.
- Assign each file a UNIQUE seven-digit phone number.
- Add the nicknames you made to the "phoneNumbers" array. NOTE: the order you add your nicknames to the array should match the sequential order of the files on your SD card. (The first slot in the array will play file "001_xxxxx.mp3", the second slot "002_xxxxx.mp3", and so on).
When you're done, upload the new code onto the Arduino.
Step 11: Measure Booth and Install Phone
Last step - hang the phone in the booth! Most old booths have screw holes that match up exactly with the holes on the backboard of old payphones, so it's really a matter of finding 1/4-inch screws with threads that fit. Screw the backboard directly into the booth's mounts, and then attach the rest of the phone to that.
I'm pretty pleased with how this turned out - the booth looks awesome, and it's a great way to hear stories about Boston's rich history over the last 60 years.