Monday, 30 November 2015

The Robot Moves!

The robot has been wired up and some rudimentary code written. It moves. The bumpers are all wired up as well and so it has collision detection.


The video shows the robot randomly moving around the workshop floor. It actually pushes all the debris on the floor to the edges of the area it covers, which is essentially what I hoped it would do. I swept the debris up with a dustpan after it stopped, which was easier than sweeping the whole floor.

Next step is to add a vacuum system so the robot collects debris rather than push it about.

Also, I'm not sure the cheap batteries I bought recently as battery packs are anywhere near the capacities they said they were. Hmm, not too much of a surprise bearing in mind the price.

Saturday, 14 November 2015

Watch Bracelet Spring Success

It looks like the latest iteration of a replacement spring for my Breitling Aerospace has been successful. After the spring died (after only 16 years...) I first tried unravelling a spring I had lying around and used it to make a replacement. It worked OK, but as the original spring had been circular it was difficult to make it a nice shape. The bracelet has a flat cavity for the spring nd it just didn't lie flat and caught on the bracelet as the spring action was exercised.

Attempt 2 (well 2,3 and 4) was a 3d printed part in PLA. It worked well and was perfectly sized. Unfortunately it opnly worked well for 2 days, then it lost all springiness and was useless.

I then bought some stainless steel wire (wire supposed to be used for safety wiring engine parts), but it was too brittle to form into a spring. It only allowed one bend, any attempt to rebend and the wire snapped.

Next attempt was piano wire. I ordered some 0.51mm piano wire and formed it into a flat spring with just a few spring elements. The original spring had a clever design that allowed quite a few elements to fold into a small space. I couldn't form it in such a complex way, so I am trying less elements. This allows the spring to fold into a small space and hence gives more extension when putting the watch on.

Wednesday, 11 November 2015

Spoon Collection

I made some wooden spoons a while back but didn't post photos as they were a present and it was all a bit hush hush. Now I can post some photos, here they are:

Acomplete set of different types and sizes.

Tuesday, 3 November 2015


I'm putting together a robot that will be used to trundle around the house, hopefully picking up dirt and so on. That's the plan anyway.

The design is an octagonal base with two stepper motors as drive wheels. An arduino Mega will control the robot, and there will be sensors for bump-detection and maybe position determination.

The stepper motors are geared down, and the gearbox has a 6mm shaft witha 5mm flat. I couldn't find any wheels that fitted that shaft so I printed some:

I'm not sure how well the elastic band tyres will work, I may have to find some other grippy way to do tyres.

The stepper motors are mounted with printed parts too:

The stepper motor drivers are individual PCBs, I printed mounts for them too:

I'm probably going to mount two battery packs, one for electronics and one for the motor drive. This should keep noise from the motors at a minimum and should also allow the electronics to still function when the motor drive is dead. I could them switch the motors to use the electronics battery pack and limp back to a charging station. For now the robot will flatten it's battery packs and they will have to be removed to be charged externally.
Anyway, more printed parts hold the battery pack:

The arduino Mega has a prototyping shield on it, where I will add extra circuitry and also attach the motor drives and sensor inputs.  It is also mounted with printed parts:

The parts are mounted on a plywood base, this is octagonal and will have bumpers on each edge for collision detection:

Bumpers next, they are a bit tricky as microswitches aren't that straightforward to mount. I've started with a single printed bumper which contains two microswitch mounts and some flexible spring parts. So far I have quite a few iterations of the bumper:

In that photo the first bumpers are on the right hand side and later iterations are to the left.
They still need a bit of work, but they are nearly there. I need to make sure the switches are operated from all directions and everywhere long the length of the bumper.

I also have an ultrasonic sensor that I may mount on a servo so I can measure distances in different directions.

Shutter Hooks
The shutters on the workshop doors have a tensioned spring that is designed to provide an assistance when lifting them. It works well and the effort required isn't too bad, even with the big shutters. At the top of the travel, however, the spring isn't under much tension, and so the shutters have a habit of drooping after they have been lifted. I thought about drilling out some lock slots in the runners, but that would have required completely dismounting and disassembling them, and I don't fancy that. So, off to the 3d printer again, and I made a hook and hinge:

 This is the hinge and hook assembled as it will be used,

and this is the hook in use on the big shutter. The force it needs to exert to hold the shutter up is very small and PLA is easily strong enough.

Watchstrap Spring Saga
The spring that allows the bracelet on my watch has broken into pieces after only 15 years of use. It's a spring that can compress to a very small volume.

My first attempt at a fix was to see if they were on ebay, but no, not really. There are some springs that may work, but they weren't definitely the correct one and were very expensive. So, attempt one at making a spring was an unwound spring bent into roughly the correct shape:

Not pretty, but it sort of worked. It wasn't quite the right length, so there was still a bit of slack.

Next attempt was a few 3d printed springs in PLA:

These are much neater and a better fit as the sizes can be tuned easily and accurately. They work well too, but only for a while. The PLA seems to creep and end up in the compressed state, i.e. sort of lose it's springiness.

I've ordered some piano wire, we'll see how that works out...

Monday, 2 November 2015

Jasper Trials Finished

Well, almost finished, I still have to slide the glass in and hang it on the wall. 

This now has the painted number, the paper labels and pencil numbering. Everything I could see on the original. The colours aren't 100% correct, but that's almost impossible from photos.