Psychic Origami

So William is a year old now and to celebrate that fact I decided to make him a table. Now given that my last piece of woodwork was a doorbell, hastily constructed using a coping saw on the doorstep of the previous house, this could have gone badly. Luckily it went pretty well. The table I’ve made has slightly wonky legs, but it’s otherwise sturdy and stable.

Next time I make something like this I’m going to try to do it better (of course). In particular I think I shall try and make some proper mortise and tenon joints, as they’ll help to keep things squarer. I opted to use dowels to pin the legs together, which meant the legs could move around too much before the glue set.

I then had to also add in some braces to the legs, which I fixed using brass screws to provide extra rigidity and strength. One good thing I did learn at this stage though, was that a tenon saw and a mitre block are a wonderful combination! Without them the legs would have been even wonkier.

Once the leg frame was made, next step was the table top. For this I leaned heavily on this guide to building a simple sturdy wooden table on the make blog. Sadly I didn’t have some of the tools used there (e.g. a router) so again made use of dowels to join the separate pieces of the table top together. This got easier once I also invested in a jig to help hold the drill bits steady and at 90°.

With a fair bit of clamping and strapping the table top came together pretty well. Though there were some small cracks left between the pieces in a couple of spots.

At this point I could then test out the table a bit.

The top was a little bit wonky. This was in large part to my poor choice of timber – I failed to check the timber was itself straight. Never the less I soldiered on and clamped the table down after applying some water to one side. After trimming the edges and sanding the table the wonkieness was less evident and things started looking much better.

Next more holes were drilled and dowels inserted to pin the top to the frame. Then after the application of a whole load of glue more clamping occurred.

This final clamping to the table top really helped to reduce the curve of the table top further.

I then applied some wood filler to the cracks in the table top and also sealed off the join between the leg frame and the table top. Then after that was all dried and sanded down a coat of clear indoor varnish was applied to the legs and underside.

At this point Heather and I decided it would be nice to add some pictures to the table. So we broke out the paints. Heather painted one of William’s pirate toys and I painted an octopus/kraken that was on some of his pyjamas.

After that the top was varnished as well. We finished doing all of this just the night before William’s actual birthday. I had started with a couple of months ahead, but it always takes longer than you think.

I’m very happy with the final outcome. It was very satisfying making something semi-sizable with my hands. I’m also starting to acquire some better tools and a few more skills, so hopefully future projects will go even better.

The main thing though is that William seems to like the table.

After a first couple of small Arduino projects I felt the need to make something a bit more useful and permanent.

I had seen Roo Reynolds talking about hacking his doorbell to get it onto Twitter and as our doorbell is a bit rubbish I thought this seemed like a good project. His hack only updated Twitter, so there was no direct physical sign that the doorbell had been rung. Given that our current doorbell is pretty rubbish anyway (it should ring, but just makes a rattling sound), I decided to start off with the physical/audible side of things and then later move on to pushing notifications out to laptops on the local network or beyond…

I’ve been documenting my progress on Flickr now for a while.

Take apart wireless doorbell

Following Roo’s approach, I picked up a cheap wireless doorbell from Tesco for about £9 and took it apart:

I was able to verify that I could turn an LED on/off with the doorbell at this stage, so I knew I could use that as a signal in the Arduino. Using a multimeter also let me figure out some more details about the voltage and current used to power the speaker:

This was about 3.1 V and 75mA output. That’s a few milliamps more than the Arduino can tolerate, so I knew I had to make sure I put a resistor (22KOhm) in between the doorbell and the Arduino. The doorbell would also need to draw power from the Arduino, but luckily the Arduino has a separate 3V output, so that wasn’t an issue.

From there I verified that when the doorbell was activated I could read a drop in voltage from the wire on the doorbell labelled “SPI”. At this point I had the input for my Arduino.

Servos and prototypes

The next step was to provide some sort of audible output. Originally I had thought about just adding a buzzer, but fancied something a bit more old-fashioned. I figured it’d be good fun if the nice 21st century tech of the Arduino used some rather more ancient technology to create sound – a bell.

Using a micro servo from Oomlout I created a couple of prototypes.

I made a pretty simple circuit to hook up the servo, doorbell and arduino:

The first prototype used some lego and a bell from a Christmas ornament:

This worked, but the servo was probably louder than the bell!

Next I got hold of a small brass bell from a music shop. Luckily the top unscrewed and would let me easily attached it to a piece of lego. So another prototype was created using the small brass bell:

This worked much better!

The bell is about 100g in weight, which isn’t massive, but when it’s flung around the lego prototype would tend to move too. Not so good when this will live on the kitchen window sill. So I’d need something sturdier for the finished version.

A little soldering

As well as trying out a better bell I also made the circuit for the bell and servo more permanent, by soldering everything up on a piece of stripboard. I also used a few headers, so most of the circuit would plug into the Arduino – like a rudimentary shield. The wire to the pin controlling the servo, was left to be plugged in separately. I hadn’t soldered anything since school, so I ended up swearing quite a bit trying to do this. For me it was probably the trickiest part of the whole exercise, but it did work in the end. Just glad I had a multi-meter with a continuity mode to find the short-circuits – a knife worked well to clear up some of those.

Woodwork

I next turned to my (t)rusty woodwork skills to create a sturdier version. First off some pieces of wood to mount the Arduino, doorbell circuit and servo:

Next came the base and first part of the bell moving arm:

Then I added the top piece of the arm as well as the picture wire to make the bell swing properly:

At this point everything worked as expected:

Tidying up

After the sawing and sanding was finished there was still some general tidying up to do.

Once I’d taped down the servo wire and antena wire with electrical tape I needed to deal with the movement of the whole piece when the arm swings out. First I got hold of some Sugru and made some small rubberised feet to prevent the bell sliding around:

The next task was to add a counter weight so the bell wouldn’t tip over. For this I made two piles of fifteen pennies, which I wrapped in electrical tape and taped to the ledge on the reverse side from the Arduino:

Eventually these will be covered up and will probably actually make up part of the internal structure of the outer decoration. This should also mean they’ll end up being attached better. For now though electrical tape has proved sufficient.

One final tweak involved inserting some small nylon washers either side of the arm:

This was done to help make the movement of the arm more consistent and slightly smoother. Previously I was finding that the arm would shift position slightly, which sometimes caused problems for the servo.

Deployment

With the hardware finished I then set about actually getting it all up and running as our real doorbell. So imagine my horror when upon placing the doorbell on our kitchen window sill and connecting the power everything went haywire and the arm just constantly moved! After some tweaking of the code and kitchen-side debugging I realised that I really should make use of the Arduino’s internal pullup resistors for the doorbell pin. Up until that point I had left it “floating”. When powered by the USB this rarely drifted to zero, so I thought it was working fine. However on mains power it regularly dropped quite low, making the Arduino think the button had been pressed, triggering the servo. Configured the pullup resistor and tweaking the activation threshold (as it was now higher than zero) sorted out this problem perfectly:

Conclusion

So we now have a slightly Heath Robinson doorbell. It works better that our old one. There’s also plenty of scope for making it do more too. In fact phase two will be mostly about connecting the doorbell to my Chumby to get it communicating with the local network.

Check out my doorbell git repository on github for the code, as well as a fritzing circuit file.

I’ve clearly picked up the making felt toys bug. For Christmas this year I ended up making a pair of felt horses for two of my cousin’s children:

I thought I’d have a go at writing up the instructions for how I did this – complete with template for making your own:

How to sew a felt horse

It’s pretty easy really. As long as you can sew some backstitch you should be able to make this easily. If not then it might not be the worst first project to try either!

It’s been a busy two months for me. I’ll soon be getting married and there’s been quite a lot to do. A while back I finished the invites for the wedding (which involved hand-stamped wrapping paper):

From there I moved on to creating a pair of robins to sit on top of the wedding cake:

The robins are made out of felt and stuffed using bits of cut-up cotton sheet (as that was all I had to hand at the time – hence also the green cotton). The legs are simply silver wire stitched into place inside, with the red-breast covering up the extra stitches needed. The eyes are just small black beads (from Beads Unlimited in Brighton, as was the silver wire).

I felt they turned out really well, so seeing as they didn’t take too long (a couple of hours each) we decided it’d be nice to make more felt creatures (following an autumn theme) for table centrepieces. Initially we planned on one creature per table, then two and so with some extra help from my bride-to-be we ended up with twenty eight felt hedgehogs:

Again the hedgehogs were made of felt. This time they were stuffed with wadding which made things easier. The spines were glued on as “fringed” bits of felt, with a special widows-peak shaped piece for the head. This time the eyes and nose were just small bits of black felt, glued in place – so as to be marginally more child-friendly. Each hedgehog body consists of three pieces of felt – two sides and a smaller bottom piece. The bottom piece makes them stand fairly levelly and also gives them a more rounded look.

Somewhere during this time I’ve also had several friends children’s first birthdays to contend with. So seeing as I was in a felt creature production mood I turned my hand to three felt toys:

I realised the other day that all thirty three of these were made during a roughly two month period – meaning one felt creation every two days! Not a bad rate of productivity I guess.

I ordered one of the new metal Macbooks on the night they came out. So far it’s been a great machine, but there has been one minor problem – it’s a different size to my old 12″ Powerbook. So obviously my old crumpler laptop case was going to be no use.

After purchasing some green cotton thread, grabbing an old pair of trousers and a couple of hours sewing (by hand) I ended up with a perfectly workable laptop sleeve for my Macbook: