Sunday, March 7, 2010

Worlds Most Useless Machine Build - Part 6

Building My Own Version of "The World's Most Useless Machine"
Part 6 - Building The Final Prototype 

I actually finished building my final working prototype just before we got knocked off-line last weekend with our crazy wind store. A week later and with a brand new wicked fast ASUS computer my lovely wife Louise bought me I finally has some time to take and edit up some photos of the box. I must admit I am really anxious now to build my first for sale machine now that I seem to have most of the kinks worked out.

Here is a video and slide show I made showing the final prototype.




I had a heck of time figuring out how to make the arm reliably close the micro switch to turn itself off. My original idea was to mount the micros switch on a an arm off the servo motor mount. That idea was fine but the idea of placing on the side between the mount and the battery holder was bad because the arm tended to bounce off the mount and open the switch instead of just settling in the off position. The solution was pretty simple to just move in on the other side of the mount so I was using the shorter length of the arm to hit the switch which naturally has less movement. Now if the slop of system allows the arm to bounce a bit where the switch is hitting doesn't have enough movement to cause the switch to re-open. Well it worked and the box works very well now! I know the wiring looks a mess. I build the proto circuit on plain perfboard and point to point wired it which took forever to build. My production version will be made on a strip board and will hopefully come out a lot more neat looking.

In case you are wondering the smiley friendly snake is a finger puppet my wife had from her soap making supplies. I think it looked funny and it worked out perfectly. She has a number of other finger puppets that would work as well so I will be able to customize the look.

I all the pieces to size on my table saw using the rip fence and my crosscut jig. I then used my Incra Router jig to make the finger joints and route the dato slots to hold the bottom and top panels. I realized while working on my SketchUp plan I had to make the lid pieces longer than the box to compensate for the saw kerf in the 45 degree split I need cut on the table saw. Another great example of designing in a 3D model before you actually cut wood to save time and money! So that made it a bit more difficult to make rather than the standard way of building the box with the top and bottom attached then to saw off the lid. I ended up in making the lid just a tad too short. My next build I will make it longer realizing I can easily sand it down to the proper length after I cut the split.



You can see the extra length added to the lid on this plan. I will also need to add some height to the box by one finger joint when I build my production model because the space between the servo motor mounts and the battery holder was really tight.

I struggles with how to hold down the access lid a bit until I figured I would just a magnet embedded in the bottom with a metal screw coming down from the lid top. I can fine adjust the screw head till it just hits the magnet and grips down firmly holding the lid quite nicely down. It takes a good amount of force to actually open the lid when you need access to adjust the delay or change the batteries.







So now it's time to work on the production model. I need to make a compact reliable circuit board, make the box a tad bigger to fit all the components nicely and make sure I get my hinges placed properly. My obsession continues!!!


Monday, March 1, 2010

Winter WindStorm 2010 Damge

We got smacked by a scary Winter Wind Storm last Thursday night. The storm had hurricane force wind gusts of +90 mph and sustained wind force of 60-70 mph. As result our town of Londonderry NH lost 99% of the power (including us). The State of NH lost ~50% of the power grid. Trees and flooding everywhere. It was like a bomb went off.

Out biggest problem was with the power failure our basement/ my workshop was flooding. We only have a 2500W generator and it was not enough to power up both sump pumps at the same time plus keep some heat going from the pellet stove. It was a major battle to keep things as under control as possible until we got power back Late Saturday night.

We still have some minor flooding in the basement but it is getting under control. I will have lots of clean up after I get all the water drained and things dry out a bit. Hopefully not too much damage.

So for now my workshop is shut down while we recover.

But the good news is all the family is fine including our numerous pets. 

Edwood

Thursday, February 18, 2010

Worlds Most Useless Machine Build - Part 5

Building My Own Version of "The World's Most Useless Machine"
Part 5 - SketchUp Model 

My First Video Blog

I think I need to be committed over this project because I know I have gone over the top now. I created a Google SketchUp model with animation to show how the machine will be built. Actually there was a good reason to make a 3D model and that was to help me figure out all the mechanical stuff. Working it all out in the virtual world is a whole bunch easier than making the actual real stuff. It's real easy to move or re-size a piece on the fly with SketchUp.

But just to prove just how far gone I am I created a couple of videos and uploaded them on YouTube. One is an animation of how the machine will work. And the second is my video blog on how I used SketchUp to help me design the machine.

Video Blog - How I used SketchUp to help me design this machine.







Let me know how the idea of a video blog works out.


Edwood

Friday, February 12, 2010

Worlds Most Useless Machine Build - Part 4

Building My Own Version of "The World's Most Useless Machine"

Design of the Wooden Box
Yay We're Talking Wood Again!

Since I am building the box from scratch I am free to design the dimensions as needed. The goal is to make it just the right size to fit the mechanism and in proportion. I choose to use 1/4" x 3 1/2" Red Oak stock to build the box with. Probably the best joinery technique for such thin stock is finger or box joints. Thinking it would be fast and easy to make a box joint jig for my table saw to cut out the parts. The ShopSmith show this week just happened to feature just such a jig. Well I made one up but it turns out you really need a special flat grounded box cutting blade to make nice tight joints. I don't happen to have one and at the price they are selling them for buying one is not on my short list.

But I do own a fabulous Incra Jig for my router table can can very easily make box joints. Again however you do need exact diameter straight bits to cut the proper joints and as luck had it my good 5/16" bit was a tad too big. My first test joint ended up fitting too loose. I did find an old 1/4" shaft bit from an economy set that was just a tad undersized. Because of the micro adjustments of the Incra Jig you can compensate for the slight under-size and this time my test joint came out really nice.

So I am confident I will be able to make some really nice finger joints for my box with my Incra Jig. It will be easy to cut some slots in the sides for the top and bottom on my table saw.

Now I just need to figure out what size the box needs to be...

Wednesday, February 10, 2010

Worlds Most Useless Machine Build - Part 3

Building My Own Version of "The World's Most Useless Machine"
Part 3 - Obsessed Much? 
 
Louise has been pointing out to me that I have been totally obsessed with this project. I admit it I am! But on the plus side I am having a ton of fun designing it and have been learning new tools (electronic types) and refreshing my skills. It's been a very long time since I just played with electronics rather than working in the field for a living. I have forgotten how much fun it is to design circuits which is why I went to school after all.

So one item on my design list I can cross off is how servo motors work. I was rather surprised how little is written about how they really work on the web. Lots about mounting tips and what controllers to use but very little about the guts of the motors. I was curious so I kept digging and found a few pretty good sites:

***** NERD ALERT ***** 

 Read the following section only if you are a nerd like myself LOL


The second site gave me a big clue about how torque was generated in a hobby servo motor and why one direction will have more than the other director. This is important because on the Useless Machine one direction will be moving the control arm up to turn off the power switch and needs more torque. Basically the position of a hobby servo motor depends on the length of a pulse between ~1ms to 2ms is. A pulse of ~1.5ms will put the servo position in the middle of it's range. The range is typically 180 degrees of movement. The direction the servo moves with the long 2ms pulses is the direction to chose to the switch.

***** END NERD ALERT *****


So now with a better understanding of how hobby servo motors work I can go about designing my control circuit.