A bit of woodwork

My ~10 year old CRT TV died, so I caved and bought a LCD TV to replace it. Pleasingly, this let me put the new TV on the wall, removing clutter from my lounge, and prompted me to get a piece of furniture for the gap between the sofa and the wall.

Unable to find anything with the right dimensions and an acceptable configuration of drawers and shelves, I decided to make my own, as follows...

Total time from concept to completion: One month.

Which is nice.

Light Canvas - LEDs 5: All the LEDs

Here are all the LEDs running - 12 panels, each with 5 LEDs. They're not fixed in place yet, just taped in the approximate location.

It turns out that the 555 dimmer circuit isn't quite right, as it seems that the LEDs aren't getting a large enough current - 0.16A, rather than 0.45A (when powering all the LEDs without the dimmer).

I guess it's something due to the transistor not putting/allowing enough current through...

Video:

Light Canvas - LEDs 4: Progress!

Having important things to do can be really motivating - for other projects. I've household repairs to organise, but can't figure out an elegant way for it to be done - so I'm ignoring that for the moment, and have made some progress on the Light Canvas :-)

Subsequent to my last post on this project, I satisfied myself that the circuit was ok, and ordered a bunch of components, and took the opportunity of a OxHack session to  breadboard the control circuit, which I did - except for the minor point that the circuit didn't actually work... Oh well, it was a nice event, and good to meet some more hackers and see what they were up to - I need to get along to more of that sort of thing!

Many months later, I've a working breadboard with the 555 astable circuit producing a pulse width modulation varied from 0-100% depending on a potentiometer. The 555 PWM doesn't have enough power to drive the LEDs directly, so it's used to control a transistor which effectively amplifies the power of the PWM enough for the LEDs. W00t!

This happened by:

1. Getting the 555 PWM working on a single LED directly,
2. then on a panel of 5 (on a breadboard) via the transistor, then (the next day),
3. making up 9 perfboard versions of the LED panel, powered via the LED.

Video evidence:

Next steps;

1. Convert the 555 circuit from breadboard to perfboard.
2. Modify the frame to house the circuit, controls, and wiring.
3. Modify the frame so the back can be attached, and hung on the wall.
4. Stretch the canvas onto the frame.
5. Install the electronics in the frame, and put it all together.
6. Put on wall and bask in its glow :-)

Light Canvas - LEDs 3: Circuit development

It's great what you can learn with some time and t'interweb - when finding time between band, family, and the rest of real life, that is...

This LED wizard (and generally informative site) helped me realise that "forward voltage" is the same as "voltage" as generally used, but relating to correctly wired in components, rather than what's coming out of the power source.

My previous tests were under-driving the LEDs not by current, but by voltage: A 12V source isn't enough to power four 3.3V LEDs - obviously 4x3.3 = 13.2V.

So, rather than four LEDs in series, I can have up to three. Three seems too few though, so after trying some different combinations, I've decided each column will have three 5mm in series, in parallel with two 3mm LEDs in series. This will add up to 420mA, which at 12V is 5.04W.

After a bit more reading I realised that just slinging a potentiometer between the power source and the LEDs wouldn't work (safely at least), as regular potentiometers won't handle power around 5 watts.

Some helpful people on the sci.electronics.basics Usenet group answered my query about what to use instead, and the consensus was to use pulse width modulation - a PWM circuit based on the 555 timer.

Although the intention with the light frame was to do something without that level of complication, it's just accelerating my schedule a bit, as PWM is something I know I'll need for other projects I have in mind.

Here's what I've got so far:

That schematic is missing quite a few important details - like values of the capacitors, diodes, and resistors surrounding the 555 chip. Oh, and there'll be 3 times the number of LEDs.

I've not yet learnt exactly why this circuit should work - specifically how the current flows around the diodes - but the basic principle is that the discrete components around the 555 tell it how long to turn pin 3 on for (the pulse width), with the variable resistor (R3) allowing manual modification of that duration.

Pin 3 goes to the base (B) of a high power resistor, telling it when to allow current to flow between its collector (C) and emitter (E) - acting as a switch between the power and the LEDs.

That gives us: a small (safe) current through the pot, making the 555 turn the transistor on & off, which varies the power going through the LEDs - controlling their brightness. Hurrah!

Now I need to satisfy myself that I understand all the circuit, and figure out the values for those discrete components to get the timing I want, then I can figure out a list of what I need to buy (AKA Bill Of Materials).

There's a possibility that I'll revisit the LED/resistor configuration to see if I can make it more efficient with a higher voltage source, but it's too late in the evening to think about that now :-)

Light Canvas - LEDs 2: Choosing and Testing

After shopping around a bit online, I bought 100 3mm and 100 5mm warm white diffuse LEDs - buying in bulk for this project and the next. As well as size, the two models differ in viewing/beam angle, and brightness. Two types to experiment with is manageable, and should let me play with brightness/diffusion.

One hundred pounds worth of LEDs don't come in a big box...





(I should've included something for scale in those pics. Nevermind.)

Once I had the frame put together, it occurred to me that three or four LEDs could be put serially in little columns on perfboard, each with their own resistor and connection to the power supply - something like the plan on the right.

Lets remove some unknowns: I want it bright, and nine columns of four LEDs should be pretty good, I reckon.

I've already got wires, resistors, and a breadboard so now I can do some testing.

For prototyping, I attached a couple of crocodile clips to a mains adaptor at it's lowest setting and ran that through a breadboard with one 5mm LED and the recommended resistor, to check that the basics were working, then bumped up the voltage to 12, as I plan to use in the final piece. That worked fine, so I put four LEDs in series and, using an online LED resistor calculator, found a (lower) value of resistor, accommodating the greater voltage drop caused by the additional LEDs (assuming a 2V drop per LED).

If I'm to learn anything here, I ought to figure the resistor stuff out myself, rather than using the online calculator.  For the moment though, I think I get the gist:

• Power source provides a electrical potential difference,
• generation of light by each LED is an electrical load, which uses some of that potential, hence
• voltage drop gives a lower effective voltage over the circuit, hence
• a lower value resistor is necessary.

I need to do some testing to see how this fits in with Ohms law so I understand it a bit better - but not right now, as there's more hands-on stuff first!

I was quite happy with the 5mm LEDs in a row of four, so did the same with the 3mm LEDs. Here's the breadboard:


...here it is lit up:


...with 80gsm paper as a diffuser:


...and with 160gsm card as a diffuser:


Of course, those pictures don't really convey the quality of the light - although they're HDR (taken with Bless N900) so they're not utterly terrible.

I'll need to play around a bit to see if I can/should use lower value resistors and get the LEDs brighter - they could take a higher current, but I need to verify that the voltages and currents used aren't going to be a fire risk, and look into whether higher current might give a significantly shorter LED lifespan - although this is probably a good point to find a canvas (or some similar looking material) to go on the front...

Light Canvas - LEDs 1: Known Unknowns

This is the more complicated part; or at least I have little idea what I'm doing when it comes to electronics. I know basic theory (e.g. Ohms law), and what various components do, but - so far - no practical experience beyond giving glowing red eyes to a toy raven.




The electronics for this shouldn't be too tricky though, as it's all simple analog circuits, with no digital components. The plan is to have:

1. A mains power source (I don't want the hassle and inefficiency of batteries), connected to an input socket in the frame, which itself connects to...
2. An on/off switch, which connects to...
3. A linear fader, to control brightness of...
4. A bunch of LEDs, set up to give an even glow through the canvas (some subtle pattern would be acceptable though).

So, onto the known unknowns:

• What voltage and amperage should the power source provide? It'll depend on the number and specification of LEDs  it'll be supplying - which I don't know yet. I'm thinking 12V is a fair place to start, and conveniently I've got a 3.5 - 12V adapter to prototype with.
• I've got a little toggle switch of the type I want to use, but don't know what power it's rated for.
• The fader could be a potentiometer - or might need to be something else, if the electrical load is too high for a pot. I bought a mixed bag of pots to play around with a while back, and it contained just one linear fader - hopefully it'll be suitable.
• LEDs - this is the biggest area of uncertainty. There are lots of LEDs with differering specifications available, and I don't know which type and how many I'm going to need for the canvas to glow like I want it to. Aspects to consider:
  
  • Brightness (enough to shine through the canvas)
  • Viewing angle (wider is better, as I want an even glow, not visible bright points)
  • Number of LEDs to use (more at lower brightness would give more even illumination)
  • Clear vs diffuse finish (at last, an easy one - diffuse)
    
  • Configuration - rows and columns, random distribution, or some other pattern?
  • How to choose and wire up the right combination of LEDs?
  • Cost - no need to start taking out loans for a hobby...

I think this a fair example of too many choices, not enough knowledge, so I decided that the only way to get started was to just buy some LEDs and fit everything else around that.

Time passing whilst I researched LEDs will be represented by this post ending, and a new one starting...

Light Canvas - Frame

I tend to think about all the different aspect of a project (in this case, frame, LEDs, canvas) at roughly the same time, gradually figuring out how each part will work, independently and together with the others. That would be an utter nightmare to write up though, so these posts will mainly focus on one aspect at a time. Let's start with the easy one: the frame

This is relatively simple - I know the dimensions of the canvas print (135x45cm), so I know I want my canvas to be 135x15cm.

I little research suggests that getting a pre-built frame this size will be difficult or expensive. To be honest, most of the research was watching YouTube videos on stretching canvases. Woodworking is kinda fun, so I elected to make this myself.

After a while trying to think of a way to add a bevel to regular planks (to make sure the canvas doesn't have lumps due to the frame, I realised I could simply use a simple beveled architrave.

The frame is simply two horizontal and two vertical pieces, glued and nailed together with mitre joints, plus vertical braces inside for strength.


Cutting a mitre joint with a plastic mitre box wasn't very accurate - I ended up sanding down the cuts, and hoping that glue would make up for where the surfaces didn't quite meet up.


Positioning the braces was one of those things where it was totally unclear how many were needed and how to space them, until the four frame pieces were laid out on the floor, at which point it was obvious that two braces at thirds of the width would be ideal. The braces are at the back of the frame, so the shouldn't stop light bouncing around the inside of the frame too much - I want the whole canvas to glow, rather than having several compartments. Here's all the pieces laid out (but not glued or nailed):


Also in that pic is a large piece of fibreboard from the Ikea clearance corner - thanks to H and Bic for letting me bring it back with us :-) This will be cut down to size, have the LEDs mounted on, and will be screwed onto the back of the frame.

In keeping with family tradition, my place is full of tools and materials in progress during all this:


Ideally I would've used some corner clamps to ensure that the frame was square when I glued the pieces together - but I don't have any, and the local DIY shop didn't have any. Instead, I lined up the pieces to a roofing square that I bought for the cupboard project, PVA glued them all, then nailed them all (with pre-drilled holes). The braces needed a bit of encouragement to keep them in the right place whilst waiting for the glue to cure.


Cut the fibreboard to size, and that's pretty much all the woodworking finished!



This is all about white light, so the frame gets painted with a matt white, to reflect as much light as possible, without specular highlights.


I'll need to make some modifications to fit electronics, but the frame is done for now.

Light Canvas

Another new project! This one started around October, and is a result of three different threads coming together:

1. I bought a canvas print for my bedroom, a rather nice false-coloured X-ray photo of flowers (probably based on Nick Veasly's work).

2. I need a decent bedside light to replace the rather inelegant broken anglepoise I use at the moment - and preferably something dimmable so I have the option to introduce myself to the day gently.
3. My guitar lights project (more on that later) has been stalled for around two years, and I could do with a simple LED project to learn and gain some experience with electronics.

The predominantly black canvas immediately suggested a short, wide white canvas emitting white light. I think it could look very cool, and give a nice diffuse light to the room through a rough canvas texture. Including a fader will allow me to control how bright it is.


The basic design is:

• A wooden frame the same width as the print, but a third of the height. I was vaguely thinking about the rule of thirds when I chose that height, but mainly it was a good fit for the space between the bedhead and print.
• White LEDs in the frame, with on/off and fader controls, and power supplied via an external switched adaptor (e.g. a typical wall-wart). The LEDs might need some sort of diffuser so the canvas emits light reasonably uniformly.
• A white canvas stretched over the frame. Obviously, this needs to be thin enough to let the LED light through, but be thick enough to be durable. It should have some texture, for the aesthetic.

From that design, there are a lot of details to work out, starting with:

• What LEDs do I need? How many? How should I arrange them? What rating power supply will they need? How do I wire it all up?
• Do I really want canvas - what other options are there?
• How do I get the frame? Buy pre-made or construct it myself?

Stay tuned for answers to all these questions and more...

Final finish

Everything thus far unpainted gets a coat, and the visible bits of the shelves get a second coat, and are left to dry.

A quick sand down the top and front (drawers and fascia), and then a second coat of paint for a smoother finish (apparently).

It might turn out that the insides of the drawers will need a second coat, or the commonly visible parts need a third - but I can always go back to it if that's the case. Probably not though.

So that's the cupboard done - de-shelved, re-shelved, and drawer-ed:

Of course, the cupboard is now mostly full with all the tools I bought in order to fit it out!

Job's a good'un :-)

Completing the chest

With the drawers in the framework, there are a few holes to fill - namely the top, and the gaps on either side of the drawers at the front. That involves getting more wood though, as I'm lacking single pieces big enough to cover the wider gap on the front right side. I figure I'll try and get a suitable off-cut from the DIY store,

The top might be filled with a piece of plywood from one of the old shelves, unfortunately it's not long enough to reach the front of the drawers - and (because the cupboard is not square) will need to be at an angle. The pic below shows the sheet of plywood square with the back and sides, but the front has a gap larger on the right than the left:

I have a couple of options here: either get a new piece of wood for the top, or fill some space at the back so the existing sheet can come forwards.

Whilst considering that, I drill, saw, file, and sand handles into the front of each drawer - just a beveled hole about the width of my hand. That's the last major cutting for the drawers, and by this point I'm a little bored, so they're probably a bit rougher than they should be. Never mind, the project is getting pretty close to completion - I can now do some finishing work: filling nail holes and gaps with wood filler, then painting using the same paint used on the cupboard (which was left over from the previous owner's DIY). It's beginning to look presentable.

A trip to my brother's to lend him a tent revealed that he had a load of offcuts from his shelving project (definitely a family trait). I found a suitable piece and nabbed it, and it took very little to cut them to site and nail them in place. With the completely flat front it looks ok - not neat enough for the modernist masterpiece I originally envisioned, but pretty fair.

I decide to go with re-using the materials I already have for the top, and with a bit of sawing and fiddling, it sits quite well:

Next up, final painting...

Drawers - part 3: Assembly

The box joints weren't especially close, so would never hold the drawers together by themselves. To make sure they didn't fall apart, I glued the joints, and then nailed them as well, recessing the nails with a nail punch so they wouldn't show in the final result.

The last drawer came together like this (shown at x15 speed):

It even fit the framework:

Alternating between routing and assembly, I put all four drawers together and - with some judicious filing of edges got them to all fit in the framework quite neatly, which was nice.

Coming up in the next post, fascia and top...

Drawers - part 2: Routing

Ok, so the Dremel router attachment was delivered and I got back to work. This turned out to be quite tedious, in a classic (not the) right tool for the job way.

The router was needed to make dado joints (simply, straight grooves) on the back, front, and sides of the drawers, and two rabbet joints on the front piece to help fix it to the sides. That's six cuts with the router per drawer, time four drawers is 24 router cuts.

Technically routing with the Dremel worked, but it took a long time to make each cut, as it wasn't powerful enough to go the full depth in one pass - typically needing 5 passes. By the last cut, it took me about 15 mins, earlier ones had taken longer whilst I was getting used to the process and tool.

Here's some video of the last dado, at 15x speed.

Admittedly it would have been quicker if my workbench wasn't so ramshackle, but then again - if I had a router table it would have taken about 5 seconds per cut...

I assembled the first drawer before routing all the parts, so what I learned while assembling it could feed into the next set of cuts. The main point was making sure that all the dado joints lined up well, by combination of measurement with a ruler, and direct comparison of one bit of wood to another.

Assembly coming up in the next post...

Assembling the framework

Here's the framework assembly video I mentioned in Framework.

Drawers - part 1

I actually did more planning for the drawers before building the framework, but didn't want to disturb the narrative ;-)

I measured the cupboard and considered how much clearance the drawers would need from either side to ensure there wouldn't be any problem opening them, then rounded the remaining space down to a convenient width of 520mm:

The sides will be shorter than the gaps; the back panel will be slightly tall (a lip at the top), to prevent the drawer being pulled out accidentally; and the front panel will cover half of the framework horizontals above and below it, except the top drawer which will cover all of the top horizontal.

The rear and sides will be connected with box joints, and the front and sides with rabbet joints. The drawer bottom will use dado joints, which will be get nailed and/or glued as well.

Now I know what sizes I need, I can work out a bill of materials, specifying all the parts I need.

Drawing up plans at home is fine, but has a problem in that you can't be sure what materials will be available in the shop. The online guides to making drawers I read suggested ply for the sides and bottoms - but the shop didn't have thick enough ply for the sides, so I picked MDF instead. Hopefully it'll be strong enough!

Once I got my newly purchased two sheets of ply and three sheets of MDF home, I was able to plan how to get the most out of them. Unfortunately there didn't seem to be a way to waste less, but I did get a bit to use as fascia beside the drawers. Different drawer sizes might have been more efficient, but it would have turned into differential equations, and that would be taking it too far...

Ideally I'd be cutting all of these bits of wood with a table saw, which would be quick, and should help keep edges straight, distances consistent, and angles correct. I don't think I've got the space for a table saw, even if I did think I'd be able to justify it.

Maybe a circular saw, which would be better than cutting everything by hand saw? Nah, still don't think I can justify it.

I had heard about the Dremel multi-tool, which is meant to do cutting, routing, sanding - you name it - and thought that it would do a lot without needing a lot of storage space. It sounds like it would be adaptable to a range of things I'll want to do for this and other projects (my LED guitar for one).

It should cutting box joints, and routing for rabbet and dado joints - I'll have one. In fact I'll also have the pillar drill accessory which I'm bound to use - maybe even instead of the router accessory.

Well, when I tried some cutting, the shape of it meant I couldn't get the right angle, and the cutting disc snapped (I think that's an intentional safety feature). So I'm back to the hand saws. Sawing the boards by hand didn't take too long, but did require a lot of edge shaving, to square everything up.

The next task is box joints, with tenon saw, hack saw, and file. If it was real wood I'd chisel it, but I expect MDF would split in all sorts of horrible ways.

After one box joint the build stalls for a while, because it feels like I'll be sawing for ever. There may have been a rather entertaining a party and a few nights out that took away some momentum as well. Anyway, a few evenings later the mood strikes me again and in just two evenings I get all the other box joints done, with the ply cut to size for the drawer bottoms as well. Progress :-)

Drawer parts with cuts for box joints:

Those MDF pieces are missing some important cuts: The rabbet joints where the front attaches to the sides, and the dado joints where the bottom fits into the front back and sides. I haven't the skill/patience do those accurately with just hand tools, so I do need a router.

The Dremel can do routing, but it's too wild to use freehand making a dado joint. Using pillar drill accessory as a router looked risky as well, so I went and ordered the router attachment. On the plus side, waiting for delivery of the router gizmo meant I started writing this stuff up...

Framework

Ok, the new shelves are in, and I have a load of wood ready to make the framework per my design:

As I want to make some proper joints, I need a few tools - a wood saw and power drill are a good start, but a back saw of some sort would help. I think it was a tenon saw I bought.

I also went on a little diversion here, spending most of one morning re-organising my tools into a tote-style tool bag, and putting screws and nails into separate compartments. I'd be worried about OCD if it didn't pay off by making things easier to find, but it does, so that's fine :-)

Anyway, the frame starts with the outside edges of a cuboid:

The edges resting on the floor are basically there to hold the four uprights in the corners, each of which have been cut at the bottom so they fit over the skirting board.

The corner joints at the top are a sort of combination of mitre and lap joints. Not the most accurate mitres ever, but the overall sizes lock it in place:

With the outer edges done, I make lap joints on the four uprights, facing the front and back of the cupboard. These are inset with horizontals going from side to side, which in turn have lap joints and corresponding horizontals going front to back.

To space the drawers from the sides, and for more vertical strength, additional vertical colums are created between the front horizontals, to be kept in place with dowels.

Most of this is in the sketches on the right side of this bit of paper:

Not very well described, but it's late, and I have a video of me on a dry-run putting it together that might show it in a comprehensible manner, in which case I'll post it. Update: Here's the video.

Here are all the framework parts ready to be set in place:

And here they are in place, with dowels, glue, and just a couple of screws to make sure it doesn't move:

I haven't mentioned the two uprights in the middle before; they're screwed to the front-back horizontals, and should stop the drawers fishtailing (as well as giving more vertical strength).
A closer view:

Note the horizontals going front to back are slightly inside the verticals - they will be supporting the drawers.

Inevitably, this produced plenty of spare wood and off-cuts - hopefully I'll have use for some of them over the rest of the build, and eventually the remainder can go in someone's BBQ, chiminea, or something:

Next up - drawers...