Memory Box with lid-triggered audio

After having our son, my partner wanted me to make her a memory box where she could keep all the trinkets and keepsakes from his birth.

As it is something of an old stereotype that such things would be kept in an old shoe box, I wanted to mimic that aesthetic.

The box is made from iroko, sides of approx 1cm, joined with box joints.
The base is simple hardboard, rebated into the sides.

I didn’t really want to add hardware such as hinges as I felt it would detract from the shoebox aesthetic, so I opted for a simple lift off lid.

The lid itself is made from a thicker piece of iroko, with trim added around the edges.

In order to provide a good friction fit, a piece of plywood, wrapped in t-shirt fabric, matching the boxes internal width and depth was added to the lid. This holds the lid on without rattling around, and incidentally hides the “bonus feature” of the box.

The bonus feature

Of course I can’t do anything normal like just make a box.

During his first few weeks, whenever our son sneezed, he would follow it up with a little noise that sounded like he was saying “oh..”. Of course it was incredibly cute and a memory we want to cherish forever.

What my partner didn’t know at the time, is I had managed to catch this on video, and I wanted to surprise her with it. 

A few years ago (around 2015-2016 I think), Sainsburys brought out a Christmas biscuit selection box which included a gadget for recording a message that would play when the biscuit tin was opened.

Somewhere along the line somebody I know must have got one, I scavenged the gadget from the tin once it was empty, and it spent the past few years sat in my electronics junk drawer, waiting for a project to be used in.

 

 

The circuit board is clearly designed as a disposable product – it is powered by 3 button cell batteries, which are riveted to the PCB itself. Whatever microcontroller powers it is hidden under an epoxy blob, and the only other notable features are a small microphone, speaker, a light dependent resistor (which is how it detects if the box is opened), and a small switch used to start and stop recording.

First thing to do was to drill out the rivets and get rid of the dead batteries.
Rather than replace them with more button cells, I opted for wiring in a AAA battery holder, I just had to follow the PCB traces and connect it at the right point.

 The microphone is pretty much as crap as you would expect for something of that size in a ostensibly disposable product, so I needed a better way to record the audio.

To do that I replaced the microphone with a 3.5mm jack and coupling capacitor. Once I’d copied over the recording, I removed that as well to save space, and also removed the record button to avoid overwriting.

 

Then it was simply a matter of hiding the electronics in the box. This was done by carving out a hollow in the middle of the lid. The ‘inner lid’ of plywood that was also used to create a friction latch, added sufficient depth to the lid in order to hide the battery and PCB.

The underside of the lid with hollow for PCB/battery and speaker.

The t-shirt fabric that covered the inner lid also hid the circuitry, while also allowing enough light to pass through to activate the recording.

ID-card Lanyard Headphones

I, like a lot of people, work in an organisation that uses access control cards that we need to carry at all times - usually on a lanyard around our neck. I also like to listen to podcasts and music while I work, so that often means having a pair of earphones around my neck too. The combination of the two often results in tangling and general annoyance, so I thought I could combine them.

I revisited the cable tidy that I previously created (it was one of the first 3D printed objects I created, and definitely in need of some improvement).
I've since moved away from OpenSCAD in favour of Blender as my 3D skills have improved - The new design can be found on Thingiverse.

The plan is use a scaled down version of the cable tidy to control the part of the earphone wire from the connector to the split


and then have each earphone attached to the lanyard, coming out at the top with enough slack to reach my ears.

The cable tidy is straightforward enough, there are three pieces - the two halves of the inner section, and the outer ring. They all friction fit - once printed, just lightly sand necessary edges until a snug fit can be achieved.

A post shared by Anthony (@darkmidnight_diy) on Dec 27, 2017 at 4:32am PST

To create the lanyard I started with two promotional ones I'd received (they tend to be a common hand-out at conferences and trade shows). The main one also has a side-release buckle just up from the dog clip (the clip that holds the card... yes, I had to Google what it was actually called), which would also solve another annoyance - having to remove the lanyard while driving to get through the car park security gate.

The second, sacrificial, lanyard, is slightly narrower. This lanyard was cut into strips which would be stitched to the main lanyard to create a channel to contain the earphone wire.

I stitched up one side, put the earphone wire in place, then stitched down the other side to lock it in place. The length of wire was too long to begin with - this was partially by design - I didn't want to leave the top (earphone side) just open, as I could forsee wear and tear putting too much strain on the stitching. What I did instead was stich it 'too high', then cut down the middle of the sacrificial lanyard to pull the earphone through and create enough slack, and then stitch up behind it, so that there was more, stronger stitching supporting it.

I repeated this exercise for the other earphone, and it was done. One snag was that the earphones had a small button halfway down the wire for the right-hand earphone, which was a little too big. A dab of contact cement held this in place, and unless looking closely, it's not noticeable.

I tested using the lanyard at work before the Christmas break. As with all wearable tech, there's always the concern that it looks too goofy, so I picked a day where the office wasn't too busy, to see what, if any comments were made. All the feedback I heard was positive - for the most part it just looks like I have the headphones resting around my neck, and as for the cable tidy, a lot of others have keys and other items hanging from their lanyards, so it doesn't seem too out of place.

Telephone audio interface

I work from home, and my job requires I spend a lot of time on the phone, particularly in conference calls.


I could easily go and just buy a new headset or hands free desk phone, but I already have a general purpose headset that I enjoy using, and frankly, I have accumulated a lot of headsets over the years from various phones, consoles, computers etc.

One of the items I had in my junk bin was an old wall-mounted telephone - the kind where the keypad is on the handset.

Taking the phone apart revealed three PCBs - one in the base unit of the phone, and 2 in the phone itself. One is obviously the keypad, and the other appears to be an amplifier - it was on this board that the microphone and speaker was attached.

Making the connections - the main part of the interface, is really very simply. Just cut away the microphone and speaker, and replace them with connectors.

The next step is the hang up button. Hang up buttons are press-to-break - pressing the button breaks the circuit, so as it stands connecting this to the phone line will result in your line being open.

To add extra complexity on the phone I was using the hang up button was a Double Pole Single throw switch (DPST) - this means that the switch effectively controls two circuits.

When closed, the switch connects the 4 contacts (seen de-soldered above) as follows: 1 & 2, 3 & 4

Fortunately I managed to find a 'normal' DPST switch on an old amplifier PCB in my junk bin, so wired that in place.

Also, in order to make the end product neater, I removed the coiled cable between the base and handset, and cut away the keypad - I can always use my existing phone to dial. Besides, the keypad may prove useful in a future project.

All that remained was to create a new case for it. I was able to recycle an old business card box, and 3D printed a basic front panel for the connectors.

The finished box, just connect an audio source to input, and some headphones/speaker to output, and away you go.