Thursday, 28 November 2024

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.


Sunday, 10 November 2024

Krups “Espresso Piano” XP521040 coffee machine repair

Since repairing the Dolce Gusto pod coffee machine a few years ago, I upgraded to a proper espresso machine, The Krups “Espresso Piano” XP521040.

It was another freebie hand-me-down from a relative who no longer wanted it, so I have no particular opinion on whether it’s a great machine compared to the competition or anything like that – it’s merely a step up from using a pod machine (with or without re-usable pods).

The problem
A while back it started acting a bit weird – especially if I was making more than one coffee – it would seemingly enter what I thought was a cleaning cycle.
It just keep pumping water out into the drip tray until I switched it off at the mains.

More recently it failed more completely. As soon as the machine was switched on at the wall (even if the machine had not been switched on by it’s own power button), it would start pumping water into the drip tray – the only way that the pump could be switched off was at the wall socket.

Diagnosis
Starting by opening the machine up from the bottom, I quickly found the controller board. 

For a consumer product, the circuit board is surprisingly well labelled.
There are a number of braided wires, connected with spade type connectors.

After a bit of probing around, I noticed that the PCB had a slight scorch mark at the base of one component. It was very small, I actually didn’t notice anything during the initial investigation - it was only when I’d just about given up and was packing away everything to dispose of that I spotted it.

The scorch mark around the leg of the failed component



 

 

 

 

 

 

 

 

 

 

 

The component in question is a BT134. This is a triac, and it is connected to the pad with the spade connector labelled “pump” – So it seemed a likely culprit.

Tracing the connections about the machine appears that the pump has a direct AC connection, so my guess as to what happened is that the component failed and it’s failure state effectively held it open instead of in a “switched off” state.

This does explain why the pump was active only with mains power, regardless of the rest of the machines state.

The fix
The fix itself was plenty straight forward. I sourced a replacement BT134, I swapped it out, which requires no more than a little bit of soldering.

Putting it all back together, I tested it and it works fine.

There’s nothing more to it really than that, I just want to write up and publish this in case it helps anyone else who may be having similar issues with our machine. But as always, these posts should be treated as a diary of what I did, and are in no way a how-to or guide. I am by no expert, what you do with information I provide is at your own risk.