house building works 2024

Building a Secret Cabinet

We’ve recently had the attics of our house converted, and I moved my bedroom up to one of the newly-constructed rooms.

To make the space my own, I did a little light carpentry up there: starting with a necessary reshaping of the doors, then moving on to shelving and eventually… a secret cabinet!

I’d love to tell you about how I built it: but first, a disclaimer! I am a software engineer, and with good reason. Letting me near a soldering iron is ill-advised. Letting me use a table saw is tempting fate.

Letting me teach you anything about how you should use a soldering iron or a table saw is, frankly, asking for trouble.

A spirit level on an unfinished shelf, under a window and beneath an uncarpeted floor. — Knowing that I’d been short on shelf space in my old bedroom, I started work on fitting shelves for my new bedroom before the carpet had even arrived.

Building a secret cabinet wasn’t part of my plan, but came about naturally after I got started. I’d bought a stack of pine planks and – making use of Ruth’s table saw – cut them to squarely fit beneath each of the two dormer windows¹. While sanding and oiling the wood I realised that I had quite a selection of similarly-sized offcuts and found myself wondering if I could find a use for them.

Dan drinks a 0% alcohol beer in front of three upright planks of wood. — The hardest part of sanding and oiling wood on the hottest day of the year is all the beer breaks you have to take. Such a drag.

I figured I had enough lumber to insert a small cabinet into one of the bookshelves, and that got me thinking… what about if it were a secret cabinet, disguised as books unless you knew where to look. Or to go one step further: what if it had some kind of electronic locking mechanism that could be triggered from somewhere else in the room².

Magpie decal 'perched' on a light switch. — There are other ways in which I’ve made my new room distinctly-“mine” – like the pair of magpies – but probably the secret cabinet is the most-distinctive.

Not wanting to destroy a stack of real books, which is the traditional way to get a collection of book spines for the purpose of decorating a “fake bookshelf” panel³, I looked online and discovered the company that made the fake book spines used at the shop of my former employer. They looked ideal: carefully shaped and painted panels with either an old-school or contemporary look.

Buuut, they don’t seem to be well-equipped for short runs and are doubtless pricey, so I looked elsewhere and found the eBay presence of Beatty Lockey Antiques in Loewstof. They’d acquired a stack of them second-hand from the set of Netflix’s The School for Good and Evil.⁴

(By the way: at time of writing they’ve still got a few panels left, if you want to make your own…)

I absolutely must sing the praises of Brad at Beatty Lockey Antiques who, after the first delivery of fake book fronts was partially-damaged in transit, was super quick about helping me find the closest-available equivalent (I’d already measured-up based on the one I’d thought I was getting) and sent a replacement.

The cabinet is just a few bits of wood glued together and reinforced with L-shaped corner braces, with a trio of thin strips – made from leftover architrave board – attached using small brass hinges. The fake book fronts are stuck to the strips using double-sided mounting tape left over from installing a bathroom mirror. A simple magnetic clasp holds the door shut when pushed closed⁵, and the hinges are inclined to “want” the door to stand half-open, which means it only needs a gentle push away from the magnetic catch to swing it open.

I mounted a Raspberry Pi Zero W into a rear corner inside the cabinet⁶, and wired it up via a relay to what was sold to me as a “large push-pull solenoid”, then began experimenting with the position in which I’d need to mount it to allow it to “kick” open the door, against the force of the magnetic clasp⁷.

This was, amazingly, the hardest part of the whole project! Putting the solenoid too close to the door didn’t work: it couldn’t “push” it from a standing start. Too far away, and the natural give of the door took the strain without pushing it open. Just the right distance, and the latch had picked up enough momentum that its weight “kicked” the door away from the magnet and followed-through to ensure that it kept moving.

A second solenoid, mounted inside the top of the cabinet, slides into the “loop” part of a large bolt fitting, allowing the cabinet to be electronically “locked”.

A Raspberry Pi Zero, relay, and solenoid assembly on the bottom outside edge of the inside of the cabinet. — I seriously must’ve spent about an hour getting the position of that little “kicker” in the bottom right *just right*.

Next up came the software. I started with a very simple Python program⁸ that would run a webserver and, on particular requests, open the lock solenoid and push with the “kicker” solenoid.

#!/usr/bin/python
#
# a basic sample implementation of a web interface for a secret cabinet
#
# setup:
#   sudo apt install -y python3-flask
#   wget https://github.com/sbcshop/Zero-Relay/blob/master/pizero_2relay.py
#
# running:
#   sudo flask --app web run --host=0.0.0.0 --port 80

from flask import Flask, redirect, url_for
import pizero_2relay as pizero
from time import sleep

# set up pizero_2relay with the two relays attached to this Pi Zero:
r1 = pizero.relay("R1") # The "kicker" relay
r2 = pizero.relay("R2") # The "locking bolt" relay

app = Flask(__name__)

# GET / - nothing here
@app.route("/")
def index():
  return "Nothing to see here."

# GET /relay - show a page with "open" and "lock" links
@app.route("/relay")
def relay():
  return "<html><head><meta name='viewport' content='width=device-width, initial-scale=1'></head><body><ul><li><a href='/relay/open'>Open</a></li><li><a href='/relay/lock'>Lock</a></li></ul>"

# GET /relay/open - open the secret cabinet then return to /relay
# This ought to be a POST request in your implementation, and you probably
# want to add some security e.g. a 
@app.route("/relay/open")
def open():
  # Retract the lock:
  r2.off()
  sleep(0.5)
  # Fire the kicker twice:
  r1.on()
  sleep(0.25)
  r1.off()
  sleep(0.25)
  r1.on()
  sleep(0.25)
  r1.off()
  # Redirect back:
  return redirect(url_for('relay'))

@app.route("/relay/lock")
def lock():
  # Engage the lock:
  r2.on()
  return redirect(url_for('relay'))

Don’t use this code as-is on any kind of open network, obviously. Follow the comments for some tips on what you’ll need to change.

Once I had something I could trigger from a web browser or with curl, I could start experimenting with trigger mechanisms. I had a few ideas (and prototyped a couple of them), including:

A mercury tilt switch behind a different book, so you pull it to release the cabinet in the style of a classic movie secret door.
A microphone that listens for a specific pattern of knocks on a nearby surface.

I had far too much fun playing about with crappy prototypes.

An RFID reader mounted underneath another surface, and a tag on the underside of an ornament: moving the ornament to the “right” place on the surface triggers the cabinet (elsewhere in the room).
The current design, shown in the video above, where a code⁹ is transmitted to the cabinet for verification.

I think I’m happy with what I’ve got going on with it now. And it’s been a good opportunity to improve my carpentry, electronics, and Python.

Footnotes

¹ The two dormer windows, wouldn’t you guarantee it, were significantly different widths despite each housing a window of the same width. Such are the quirks of extending a building that the previous occupier had previously half-heartedly tried to extend, I guess.

² Why yes, I am a big fan of escape rooms. Why do you ask?

³ For one thing, I live with JTA, and I’m confident that he’d somehow be able to hear the silent screams of whatever trashy novels I opted to sacrifice for the good of the project.

⁴ As a bonus, my 10-year-old is a big fan of the book series that inspired the film (and a more-muted fan of the film itself) and she was ever-so excited at my project using real-life parts of the set of the movie… that she’s asked me to make a similar secret cabinet for her, when we get around to redecorating her room later in the year!

⁵ If I did it again, I might consider using a low-powered electromagnetic lock to hold the door shut. In this design, I used a permanent magnet and a pair of latch solenoids: one to operate a bolt, the second to “kick” the door open against the pull of the magnet, and… it feels a little clumsier than a magnetic lock might’ve.

⁶ That double-sided mounting tape really came in handy for this project!

⁷ Props to vlogger Technology Connections, one of whose excellent videos on the functionality of 1970s pinball tables – maybe this one? – taught me what a latch solenoid was in the first place, last year, which probably saved me from the embarrassment of trying to do this kind of thing with, I don’t know, a stepper motor or something.

⁸ I’m not a big fan of Python normally, but the people who made my relays had some up with a convenience library for them that was written in it, so I figured it would do.

⁹ Obviously the code isn’t A-B; I changed it temporarily for the video.

Framing Device

Doors

As our house rennovations/attic conversions come to a close, I found myself up in what will soon become my en suite, fitting a mirror, towel rail, and other accessories.

Wanting to minimise how much my power tool usage disturbed the rest of the house, I went to close the door separating my new bedroom from my rest of my house, only to find that it didn’t properly fit its frame and instead jammed part-way-closed.

“Oh,” I said, as the door clearly failed to shut, “Damn.”

Somehow we’d never tested that this door closed properly before we paid the final instalment to the fitters. And while I’m sure they’d have come back to repair the problem if I asked, I figured that it’d be faster and more-satisfying to fix it for myself.

Homes

As a result of an extension – constructed long before we moved in – the house in Preston in which spent much of my childhood had not just a front and a back door but what we called the “side door”, which connected the kitchen to the driveway.

Unfortunately the door that was installed as the “side door” was really designed for interior use and it suffered for every winter it faced the biting wet North wind.

My father’s DIY skills could be rated as somewhere between mediocre and catastrophic, but his desire to not spend money “frivolously” was strong, and so he never repaired nor replaced the troublesome door. Over the course of each year the wood would invariably absorb more and more water and swell until it became stiff and hard to open and close.

The solution: every time my grandfather would visit us, each Christmas, my dad would have his dad take down the door, plane an eighth of an inch or so off the bottom, and re-hang it.

Sometimes, as a child, I’d help him do so.

Planes

The first thing to do when repairing a badly-fitting door is work out exactly where it’s sticking. I borrowed a wax crayon from the kids’ art supplies, coloured the edge of the door, and opened and closed it a few times (as far as possible) to spot where the marks had smudged.

Fortunately my new bedroom door was only sticking along the top edge, so I could get by without unmounting it so long as I could brace it in place. I lugged a heavy fence post rammer from the garage and used it to brace the door in place, then climbed a stepladder to comfortably reach the top.

A small box plane perched atop a sloping door. — I figured I’d only need to remove a few millimetres, so I didn’t mind doing it from atop a stepladder. Hey: here’s a fun thing – when I think about planing a door with my grandfather, I think in inches; when I think about doing it myself, I think in metric!

Loss

After my paternal grandfather died, there was nobody left who would attend to the side door of our house. Each year, it became a little stiffer, until one day it wouldn’t open at all.

Surely this would be the point at which he’d pry open his wallet and pay for it to be replaced?

A middle-aged man carrying walking poles on an urban riverbank drags a car tyre that's chained to his waist. — I’m not sure there’s a more apt metaphor for my dad’s ability to be stubborn than this photo of him dragging a tyre around Gateshead as a training activity for an Arctic expedition.

Nope. Instead, he inexpertly screwed a skirting board to it and declared that it was now no-longer a door, but a wall.

I suppose from a functionalist perspective he was correct, but it still takes a special level of boldness to simply say “That door? It’s a wall now.”

Sand

Of all the important tasks a carpenter (or in this case, DIY-er) must undertake, hand sanding must surely be the least-satisfying.

But reaching the end of the process, the feel of a freshly-planed, carefully-sanded piece of wood is fantastic. This surface represented chaos, and now it represents order. Order that you yourself have brought about.

Often, you’ll be the only one to know. When my grandfather would plane and sand the bottom edge of our house’s side door, he’d give it a treatment of oil (in a doomed-to-fail attempt to keep the moisture out) and then hang it again. Nobody can see its underside once it’s hung, and so his handiwork was invisible to anybody who hadn’t spent the last couple of months swearing at the stiffness of the door.

A paintbrush applies white paint to the top of a door. — Swish, swish. *Now* I’m glad I sanded.

Even though the top of my door is visible – particularly visible, given its sloping face – nobody sees the result of the sanding because it’s hidden beneath a layer of paint.

A few brush strokes provide the final touch to a spot of DIY… that in provided a framing device for me to share a moment of nostalgia with you.

Sweep away the wood shavings. Keep the memories.

Zap

This week, I received a ~240V AC electric shock. I can’t recommend it.

A 10-year-old girl hangs from a scaffolding pole outside a white house. — As you may have guessed based on photos in previous posts, our house is currently wrapped in ~~a convenient climbing frame~~ scaffolding.

We’re currently having our attic converted, so we’ve had some electricians in doing the necessary electrical wiring. Shortly after they first arrived they discovered that our existing electrics were pretty catastrophic, and needed to make a few changes including a new fusebox and disconnecting the hilariously-unsafe distribution board in the garage.

Lifted floor showing central heating pipes and a tangle of electrical cables. — The owner before last of our house worked for SSEN and did all of his own wiring, and left us a rats’ nest of spaghetti wiring that our electricians described as being unlike anything they’d ever seen before. Also a literal rats’ nest under the decking, but we got rid of that already.

After connecting everything new up they began switching everything back on and testing the circuits… and we were surprised to hear arcing sounds and see all the lights flickering.

The electricians switched everything off and started switching breakers back on one at a time to try to identify the source of the fault, reasonably assuming that something was shorting somewhere, but no matter what combination of switches were enabled there always seemed to be some kind of problem.

Electricity shining a torch into a cupboard containing an fusebox with an open cover; the switches are in a mixture of on and off positions. — You know those escape room puzzles where you have to get the right permutation of switch combinations? This was a lot less fun than that.

Noticing that the oven’s clock wasn’t just blinking 00:00 (as it would after a power cut) but repeatedly resetting itself to 00:00, I pointed this out to the electricians as an indicator that the problem was occurring on their current permutation of switches, which was strange because it was completely different to the permutation that had originally exhibited flickering lights.

I reached over to point at the oven, and the tip of my finger touched the metal of its case…

Blam! I felt a jolt through my hand and up my arm and uncontrollably leapt backwards across the room, convulsing as I fell to the floor. I gestured to the cooker and shouted something about it being live, and the electricians switched off its circuit and came running with those clever EM-field sensor pens they use.

Somehow the case of the cooker was energised despite being isolated at the fusebox? How could that be?

I missed the next bits of the diagnosis of our electrical system because I was busy getting my own diagnosis: it turns out that if you get a mains electric shock – even if you’re conscious and mobile – the NHS really want you to go to A&E.

At my suggestion, Ruth delivered me to the Minor Injuries unit at our nearest hospital (I figured that what I had wasn’t that serious, and the local hospital generally has shorter wait times!)… who took one look at me and told me that I ought to be at the emergency department of the bigger hospital over the way.

Off at the “right” hospital I got another round of ECG tests, some blood tests (which can apparently be used to diagnose muscular damage: who knew?), and all the regular observations of pulse and blood pressure and whatnot that you might expect.

And then, because let’s face it I was probably in better condition than most folks being dropped off at A&E, I was left to chill in a short stay ward while the doctors waited for test results to come through.

Two electricians, one in a hard hat, look in an outdoor metering cupboard by torchlight. — Apparently our electricity meter blew itself up somewhere along the way, leaving us with even less of a chance to turn the power back on again.

Meanwhile, back at home our electricians had called-in SSEN, who look after the grid in our area. It turns out that the problem wasn’t directly related to our electrical work at all but had occurred one or two pylons “upstream” from our house. A fault on the network had, from the sounds of things, resulted in “live” being sent down not only the live wire but up the earth wire too.

That’s why appliances in the house were energised even with their circuit breakers switched-off: they were connected to an earth that was doing pretty-much the opposite of what an earth should: discharging into the house!

It seems an inconceivable coincidence to me that a network fault might happen to occur during the downtime during which we happened to have electricians working, so I find myself wondering if perhaps the network fault had occurred some time ago but only become apparent/dangerous as a result of changes to our household configuration.

I’m no expert, but I sketched a diagram showing how such a thing might happen (click to embiggen). I’ll stress that I don’t know for certain what went wrong: I’m just basing this on what I’ve been told my SSEN plus a little speculation:

By the time I was home from the hospital the following day, our driveway was overflowing with the vehicles of grid engineers to the point of partially blocking the main street outside (which at least helped ensure that people obeyed our new 20mph limit for a change).

A driveway full of vehicles spills out onto the nearby road. — We weren’t even able to get our *own* car onto our driveway when we got back from the hospital.

Two and a half days later, I’m back at work and mostly recovered. I’ve still got some discomfort in my left hand, especially if I try to grip anything tightly, but I’m definitely moving in the right direction.

It’s actually more-annoying how much my chest itches from having various patches of hair shaved-off to make it possible to hook up ECG electrodes!

Anyway, the short of it is that I recommend against getting zapped by the grid. If it had given me superpowers it might have been a different story, but I guess it just gave me sore muscles and a house with a dozen non-working sockets.

Cable Gore

If you enjoy a bit of “cable gore”, let me introduce you to the fusebox cupboard at my house, with its plethora of junctions, fuses, breakers, switches, timers, and cabling everywhere! Banana for scale.

Installation of Windows has Stalled

I was told Windows installation should take less than 20 minutes, but these ones have been sitting outside my house all day while the builders sit on the roof and listen to the radio. Do I need a faster processor? #TechSupport

Household Finances Revisited

Almost a decade ago I shared a process that my domestic polyfamily and I had been using (by then, for around four years) to manage our household finances. That post isn’t really accurate any more, so it’s time for an update (there’s a link if you just want the updated spreadsheet):

Dan, wearing a WordPress Pride "rainbow flag on black" t-shirt, sits on a park bench alongside a French Bulldog (with her tongue sticking out) and a young boy (throwing a peace sign, wearing a pink cycle helmet and a blue school uniform). — Our household costs have increased considerably over the last decade, not least because children and pets are *expensive* (who knew?).

Sample data

For my examples below, assume a three-person family. I’m using unrealistic numbers for easy arithmetic.

Alice earns £2,000, Bob earns £1,000, and Chris earns £500, for a total household income of £3,500.
Alice spends £1,450, Bob £800, and Chris £250, for a total household expenditure of £2,500.

Model #1: Straight Split

We’ve never done things this way, but for completeness sake I’ll mention it: the simplest way that households can split their costs is by dividing them between the participants equally: if the family make a £60 shopping trip, £20 should be paid by each of Alice, Bob, and Chris.

My example above shows exactly why this might not be a smart choice: this model would have each participant contribute £833.33 over the course of the month, which is more than Chris earned. If this month is representative, then Chris will gradually burn through their savings and go broke, while Alice will put over a grand into her savings account every month!

Photograph of the Statue of Lenin in Independence Square, Minsk: Government House #1 stands behind a large metal statue of Vladimir Lenin, looking to his right. — “Land, Bread, Peace… and Spreadsheets!”

Model #2: Income-Assessed

We’re a bunch of leftie socialist types, and wanted to reflect our political outlook in our household finances, too. So rather than just splitting our costs equally between us, we initially implemented a means-assessment system based on the relative differences between our incomes. The thinking was that somebody that earns twice as much should contribute twice as much towards the costs of running the household.

Using our example family above, here’s how that might look:

Alice earned 57% of the household income, so she should have contributed 57% of the household costs: £1,425. She overpaid by £25.
Bob earned 29% of the household income, so he should have contributed 29% of the household costs: £725. He overpaid by £75.
Chris earned 14% of the household income, so they should have contributed 14% of the household costs: £350. They underpaid by £100.
Therefore, at the end of the month Chris should settle up by giving £25 to Alice and £75 to Bob.

By analogy: The “Income-Assessed” model is functionally equivalent to splitting each and every expense according to the participants income – e.g. if a £100 bill landed on their doormat, Alice would pay £57, Bob £29, and Chris £14 of it – but has the convenience that everybody just pays for things “as they go along” and then square everything up when their paycheques come in.

Photograph showing a detached white house clad in scaffolding, under a clear blue sky. — You know what else is surprisingly expensive? Having the roof of your house taken off.

Over time, our expenditures grew and changed and our incomes grew, but they didn’t do so in an entirely simple fashion, and we needed to make some tweaks to our income-assessed model of household finance contributions. For example:

Gross vs Net Income: For a while, some of our incomes were split into a mixture of employed income (on which income tax was paid as-we-earned) and self-employed income (for which income tax would be calculated later), making things challenging. We agreed that net income (i.e. take-home pay) was the correct measure for us to use for the income-based part of the calculation, which also helped keep things fair as some of us began to cross into and out of the higher earner tax bracket.
Personal Threshold: At times, a subset of us earned a disproportionate portion of the household income (there were short periods where one of us earned over 50% of the household income; at several other times two family members each earned thrice that of the third). Our costs increased too, but this imposed an regressive burden on the lower-earner(s), for whom those costs represented a greater proportion of their total income. To attempt to mitigate this, we introduced a personal threshold somewhat analogous to the income tax “personal allowance” (the policy that means that you don’t pay tax on your first £12,570 of income).

Eventually, we came to see that what we were doing was trying to patch a partially-broken system, and tried something new!

Model #3: Same-Residual

In 2022, we transitioned to a same-residual system that attempts to share out out money in an even-more egalitarian way. Instead of each person contributing in accordance with their income, the model attempts to leave each person with the same average amount of disposable personal income at the end. The difference is most-profound where the relative incomes are most-diverse.

With the example family above, that would mean:

The household earned £3,500 and spent £2,500, leaving £1,000. Dividing by 3 tells us that each person should have £333.33 after settling up.
Alice earned earned £2,000 and spent £1,450, so she has £550 left. That’s £216.67 too much.
Bob earned earned £1,000 and spent £800, so she has £200 left. That’s £133.33 too little.
Chris earned earned £500 and spent £250, so she has £250 left. That’s £83.33 too little.
Therefore, at the end of the month Alice should settle up by giving £133.33 to Bob and £83.33 to Chris (note there’s a 1p rounding error).

That’s a very different result than the Income-Assessed calculation came up with for the same family! Instead of Chris giving money to Alice and Bob, because those two contributed to household costs disproportionately highly for their relative incomes, Alice gives money to Bob and Chris, because their incomes (and expenditures) were much lower. Ignoring any non-household costs, all three would expect to have the same bank balance at the start of the month as at the end, after settlement.

By analogy: The “Same-Residual” model is functionally equivalent to having everybody’s salary paid into a shared bank account, out of which all household expenditures are paid, and at the end of the month everything that’s left in the bank account gets split equally between the participants.

Screenshot showing a sample filled verison of the spreadsheet. — Our version of the spreadsheet has inherited a lot of hacky edges, many for now-unused functionality.

We’ve made tweaks to this model, too, of course. For example: we’ve set a “target” residual and, where we spend little enough in a month that we would each be eligible for more than that, we instead sweep the excess into our family savings account. It’s a nice approach to help build up a savings reserve without feeling a pinch.

I’m sure our model will continue to evolve, as it has for the last decade and a half, but for now it seems stable, fair, and reasonable. Maybe it’ll work for your household too (whether or not you’re also a polyamorous family!): take a look at the spreadsheet in Google Drive and give it a go.