Sekret Project!

[Greebo]

(yes I know how to spell secret)

So while browsing the web one day, I came across a project some German students did making a Harry Potter style clock that instead of telling the time, tells to location of people (using their phone, either through GPS or manual updates).
http://magicclock.de/
And another by someone else:
http://www.themagicclock.com/

And I thought to myself, "I can do that!"

My inlaws co-own a place in Maine that we go to every year, and that's rented out during the summer so my goal is to make such a device by August, and leave it for renters to use (because a lot of them have kids).

Of course, the project isn't really a secret from you guys, it's a secret from the family and friends that will be there in August, so, unless anyone objects, I wish post a build log of this project here.
It could be entertaining because in terms of workshop skills I'm pretty much at zero. The programming side won't be a problem I hope!

I'll do day 1 in a post below (today was day 1) and then you can tell me to shut up if you want.

[Greebo]

Day 1: New Toys!

Programming progress:
I've been playing with an Arduino starter kit for a while, and with a view to doing this project, I prototyped a program that would poll against a web server every 30 seconds and pull down a number between 1 and 12 and adjust the rotation of a servo motor accordingly. With a bit of tweaking, making it work for 4 servos shouldn't be an issue.

So I've bought 4 servos that can go 360 degrees (My current servo goes 180, but I do *not* want to deal with gear ratios to multiply that up to a 360 degree gear, that's way beyond me!), a new arduino board and various bits and pieces to get that going. I won't be touching programming again until the hardware is in place. I can do the programming with little issue I think.

My place is to build a password protected website that runs Sencha Touch (an html5 framework that lets you build mobile apps that are cross-compatible with most smart phones). Likely the password will rotate per renter group.

Hardware
First I went to eBay and bought a clock case. My primary need was something with enough room to work in and with a large face. I very much wanted a large cuboid (like the top of a Grandfather clock) but in the end I settled for a wall clock that seemed to fit the bill. The open face area has a 10" diameter. Ignore the 2 bits of wood being glued inside, they're going to support a strut that will help support the mechanism but were not part of the original purchase:

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I live in an apartment in NYC. My toolkit prior to last weekend consisted of a hammer and 2 screwdrivers...I had to ramp up my tools. I also had to buy hardware components to make the machine work.

I'm basing a lot of what I'm doing on the 2nd link in my first post (www.themagicclock.com). So I bought 8 identical gears, brass tubes of differing diameters (that will nest within each other), various hub mounts that will let me attach the gears to the tubes and some shafts to attach to the servo motors.

Tool wise I went out to home depot and bought a cordless drill, a small portable work bench and a jigsaw. I also bought a tube cutter (the tubes are 12" each and need to be cut to different lengths) and 1/2x6x48" board.

My plan for the clock face was to make it circular (using the jigsaw...I'm a bit scared of trying that!) and glue together 2 pieces of board, to make a 12" square board. Then I hit upon a different idea which is what I'm going with: The face will be split down the middle and open outwards like a pair of doors. This should give me easy access to the mechanism for maintenance etc.

When I measured the board, I hit my first problem which was that it was in fact 5.5" wide. I also did some calculations based on the hinges we bought and realised the face would need to be 13.5" wide! So I had to cut longer boards and then some strips to glue to the sides of the boards to make them wide enough.

Did you know that if you go too fast trying to cut a straight line with a jigsaw that it might go a bit wrong?

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But I managed to get it close enough in the end. The boards are glued together nicely and with a bit of sanding, the split where the 2 sides meet should be pretty flat. (The face of the clock will ultimately be a thick card or something, so it doesn't have to be perfect)

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The rest of today was spent doing as much sawing as I could (so as not to annoy the neighbours too much - I figured most would be out today). As far as I can tell the only sawing I have left is doing the circular face. Not insignificant I know but hopefully that's it

I also drew out a couple of plans that let me see where the 4 driving gears would need to be placed. I realised that a servo motor with a shaft attached was much taller than I anticipated, *and* I had to do some extra spacing on the middle gears because I bought screws that were 1/8" longer than I needed to. Doh!
But if I figured out that if I mount 2 of the motors upside down I should be fine.
The top view shows the spacing of the gears (the gap between each gear is where the teeth mesh). The placement of the servos is not on here yet but I'll add that soon.

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The side view isn't complete yet but will help me calculate how long to make each of the tubes and where on the tube the gears will go. The other measurements are where I'll need to secure the struts that the motors will attach to.

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Goals for next time

I won't be able to do any work on this tomorrow but the weekend should be good.
I need to source material for the hands of the clock (maybe balsa wood, painted black - working with metal would be ideal but I have neither the tools nor the skill set to do that!) and take that into consideration with length of the tubes.
Assuming I sort that out properly, I hope to have the motors and gears in place, the door seam sanded and, with any luck, the door made circular. If I have time, I'll start getting the rest of the circuitry in place.

[Peahats]

I feel like your colleagues don't want you spying on them! But this is really cool nonetheless.

[NerevarineKing]

Ah, an Arduino! I've been wanting to mess around with one of those...
Very cool project Greebo!

[Greebo]

Ah, an Arduino! I've been wanting to mess around with one of those...

If you ever have time to do so, I highly recommend getting their official starter kit. The projects are small and build on each other, so it helps you get an excellent grasp of the basics. A friend of mine tried to jump in the deep end but had trouble learning it (we're both programmers).

[Dog]

I've been meaning to get one of those too. Arduinos are awesome.

For years, I worked with PICs, building my own hardware and programmers. I used to teach my electrical engineering Grade 12s the 16C84, complete with assembly language programming. Happy times.

BTW, Greebster, this is project of yours is just excellent. Thanks for posting and I'll be watching this space avidly.

Oh and the imperial measurements made me smile! I'd have to convert them all to millimetres for it to make any sense

[shimmybot]

I've been meaning to get one of those too. Arduinos are awesome.

For years, I worked with PICs, building my own hardware and programmers. I used to teach my electrical engineering Grade 12s the 16C84, complete with assembly language programming. Happy times.

BTW, Greebster, this is project of yours is just excellent. Thanks for posting and I'll be watching this space avidly.

Oh and the imperial measurements made me smile! I'd have to convert them all to millimetres for it to make any sense

Dangit dog, why'd you have to goto redacted, that sounds like it would have been fun

[Greebo]

Hrm....I may or may not have hit a technical issue.

I put the clock face doors on today (photos etc later) but then I realised that in order to give the clock doors enough clearance to open, the hands would have to be pretty far away from the face.

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As an example, in the picture above, the piece of wood on the tube is just under a half inch thick. In order to give the doors enough clearance to open, the hand must be 1 1/2 inches away from the face. Obviously, the thinner the hand, the closer it can be to the face but I'd really want it to be as close as possible and let the hands be whatever shape they want.

I have 2 options here I think.
The first is that this may not actually be an issue: The piece of wood in the picture is staying in place without any glue or anything and will turn with the tube. My worry is that it may not always be the case, repeated removal of the hands may results in the holes becoming larger etc. I could solve this with something like blue-tak but that would be...tacky. Having said that, I don't anticipate needing to open the clock face a lot either, so maybe so long as extra hands are available this wouldn't be an issue.

The second option is to somehow create removable hands. To clamp the gears to the tubes within the clock, I'm using these hub mounts:
http://www.servocity.com/html/0_770__se ... _hubs.html
If there was something similar I could use to secure the hands to the tubes, which would also allow me to remove them again, that would be ideal. But I have no idea if that's achievable at all or not.

Anyone got any ideas?





Edit: I made some holes in various scrap bits of wood and tested how well they stay on the tubes - I've decided this isn't an issue after all (though I'd still like to hear ideas for removable hands if anyone has one)

[Greebo]

Day 2: User error!

Hit some issues today, but nothing that can't be recovered.
We had a brainwave regarding the shape of the face. Rather than make it a circle, we decided that because the clock case's outer rim is an octagon, the face itself should also be an octagon! The idea being that this should be an easier thing to cut.

Did you know how to calculate the largest octagon which can fit in a square? I didn't!
Thankfully that genius known as "The Internet" stepped in to my aid:
http://mathforum.org/library/drmath/view/64103.html

So, duely informed, I created an octagon from a 13.5" square...oops

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I must have mis-calculated how big I wanted the face to be. I then shaved off an inch from each dimension. Much better:

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I installed a strut across the face of the clock, this will help support the central mechanism of the clock when the doors are open. One 1/4 inch hole later:

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In a fit of enthusiasm I decided I had to see how it might look with the doors on the hinges. Mostly this was so that I could make sure the hole in the doors and the hole in the strut lined up nicely...which it did!

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And doors open:

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Then I hit a pretty major issue.
For the shafts I bought brass tubes by K&S tubing. I got 2 packs each of which contained 3 tubes of different sizes. The idea being that each size can nest within the next biggest. The tubes are designed to be flexible but mostly I have no issue straightening them out, however the 2 smallest ( a 3/32 inch and 1/8 inch ) have proven both too flexible and difficult to cut.
So I need to buy a 2 tubes that are the next sizes up. Obviously this will mean changing the holes I've already drilled and I'll need to buy an bigger hub for one of the gears. The tube I can hopefully get in the city, the hub I'll have to order. No biggy!

[Inner]

The first is that this may not actually be an issue: The piece of wood in the picture is staying in place without any glue or anything and will turn with the tube. My worry is that it may not always be the case, repeated removal of the hands may results in the holes becoming larger etc. I could solve this with something like blue-tak but that would be...tacky. Having said that, I don't anticipate needing to open the clock face a lot either, so maybe so long as extra hands are available this wouldn't be an issue.

The second option is to somehow create removable hands. If there was something similar I could use to secure the hands to the tubes, which would also allow me to remove them again, that would be ideal. But I have no idea if that's achievable at all or not.

Anyone got any ideas?
Edit: I made some holes in various scrap bits of wood and tested how well they stay on the tubes - I've decided this isn't an issue after all (though I'd still like to hear ideas for removable hands if anyone has one)

I too am following this project with interest! A very cool idea.

Your current attachment method, "friction fit", will probably work for quite a while given the lightweight hands and such. Certainly good enough for testing purposes at any rate. A more lasting solution would probably involve a screw and a nut. Something as simple as epoxying a small brass machine screw into the end of your tube. Slip the hands over the screw and secure with an "acorn nut". Or the reverse: epoxy a nut into your tube and then a brass screw to hold the hands to the nut. A nice selection of thin hands can be found at http://www.klockit.com/depts/Hands/dept-5.html.

[Greebo]

Thanks Inner, I shall look into that!

I have all the components to build the inner workings now (I think).

Last night, I almost went about cutting the tubes and assembling the central mechanism when I realised that I'd made a mis-calculation on the relationship between tube length and gear position. Rather than try and figure it out while I was tired, I figured I'd wait til either tonight or the weekend.
There shall be a lot of assembly going on over the next few days!

I do need to practice carving out the shape of the hinges into the doors, so they the door ultimately lies flush against the surface of the outer ring of the clock. Currently the hinges raise it outwards by about 3/16". To be extra complicated, the hinge has curves (because why make things easy for yourself?)
I have the tools to do it...I've just never done it! Hurrah for scrap pieces of wood!

[M's]

I have 2 options here I think.
The first is that this may not actually be an issue: The piece of wood in the picture is staying in place without any glue or anything and will turn with the tube. My worry is that it may not always be the case, repeated removal of the hands may results in the holes becoming larger etc.

What if you drilled a small hole in the spindle end, then using a coping saw cut a slot from the end to the spindle mount, then use a small bolt/screw and nut to in effect clamp the hand to the spindle.
Using my fantastic power of Paint here is what I was suggesting. Views are from the face, side, and back of hand.

[Greebo]

Thanks mlite - that's a pretty good idea!


I got so frickin close with the central mechanism today. I'm out for the rest of the day, so no more work until tomorrow, but here's how close I got:

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I'll explain most of that tomorrow (including why the hell I had to use some duct tape) but the issue is that the outermost pipe is hitting the nuts of the 3rd gear from the bottom (rather than resting on the gear itself). I have to reverse the 3rd gear so that the screws point downwards instead of up. Not too hard but just a pain in the ass!

[Greebo]

Day...something:

The central mechanism is done!

So here's a run down of what makes up the mechanism.
I bought a bunch of K&S Brass tubes. These tubes come in increments of 1/32" with each increment able to fit within the next biggest. Originally I bought the 6 smallest tubes available, but in doing so discovered 2 things: The first is that those were too small to stay straight enough (they pipes were designed to bend, but these bent too much). And then I discovered that then you cut a pipe, the cutter tends to bevel the end inwards a little. The cutter has a tool to help fix this, but if you only have 1/32" to play with, it's not much margin for error.

So ultimately I took the 4th and 6th largest tubes from my original set and added 4 more tubes, each at 1/16" increments (3/8 "- 1/2"). The difference sounds marginal but it gives you more margin for error.
(Sorry, I'm not just being boring, there's a reason for me telling you this, which I'll get to in a moment).

Next I bought some hubs (with bores of differing diameters) and gears. They all came from the same place, so the hubs and gears match nicely:

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The tubes were cut to different lengths. It almost went entirely to plan except I had to reverse the position of the 3rd wheel so the gears are not spaced as evenly as I had hoped.

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The hubs obviously had the tubes going through them and this is why I was banging on about the tube diameters above. The hubs I bought matched *exactly* the diameter of each tube I bought. Unfortunately that made it pretty difficult to push the tubes through the hubs. If/when I do this again, I think I would buy each tube 1/32" smaller than the ones I have. The hubs would still fit pretty nicely and be far easier to get onto the tubes.
The only hub I couldn't get the exact fit on was for the 7/8" tube. So I wrapped it in duct tape and used a 1/2" hub instead.

Put it together and you get this:

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So the outer tube is basically stuck in place through the support strut. I might glue it there, but it seems pretty secure without doing that.
Running through the whole length is the smallest tube. There's a washer glued to the back of the clock case that it can sit in. A second washer is glued to the smallest tube to just help stop things sliding off (I doubt it'll happen but just in case) at the outer end. I can slide the smallest tube completely out if I want which will let me add the hands later.


Of course, progress can't happen without another hiccup:
I put together some wooden supports for the servo motors that will drive the gears, that bit went fine, but then I discovered that all the screws I had were a little short for attaching the supports to the clock case. So another trip to the hardware store tomorrow for me!

Left to do:

• Screw the servo motors + supports to the case.
  Recess the hinges on the doors, then attach the doors to the case again.
  Design the hands (each hand needs some kind of unique identifier) and the clock face (my wife's task in all this).
  Programming!

[Greebo]

Ack

For every piece of progress, there's a new wall to hit!

I got the gears all installed! (apologies for the crap picture, I haven't had time to take one in daylight yet):

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Ultimately I did not screw the support blocks to the side, I kept getting things *almost* lined up but not quite. Plus holding them in place while driving the screws turned out to be tricky. So I used wood glue instead. I doubt this will cause any structural issues because the motors are fairly light.


Anyway, so just now I tried attaching the arduino board that was running my prototype program, to see what needed adjusted (e.g. the prototype was running against a servo that only went 180 degrees, while the clock's servos are "continuous rotation").
But instead of doing anything remotely predictable, it did this (the top most wheel has a slight wobble to it, but nothing alarming):

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Round and round it goes, where it stops, nobody knows!
Turns out that a continuous rotation servo behaves differently to a regular one. I don't know if this means new servos or not yet, but it's a tad annoying.
The reason it started turning as soon as I plugged in, was that the first thing the program does is set the angle on the motor to 0 degrees (i.e. noon on a clock). But when you feed that to the continuous servo, it means "turn at full speed in one direction" while 180 would be "turn at full speed in the other direction". Of course, how silly of me not to know that (!)

Anyway, I shall try a new program before giving up on these. I do have some hope because of this writeMicroSeconds command listed here:
http://arduino.cc/en/Reference/ServoWriteMicroseconds - we shall see.


It's not all bad news though, I tried a couple of the motors and while they turned, the other wheels stayed stationary! Concept is at least proven.