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Rob Spiegel
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Impressive gadget
Rob Spiegel   10/18/2013 11:13:16 AM
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This is quite an impressive gadget -- and useful as well. Hats off to our young inventor.

78RPM
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Platinum
Re: Impressive gadget
78RPM   10/18/2013 5:08:24 PM
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I've read a lot of Gadget Freak projects in the past couple of years and this is about as impressive and as useful as any of them. It's hard to believe this comes from a teen inventor. He has a bright future in engineering. I was also impressed with the quality of technical writing. I'm not sure if he had a good proof reader or editor, but the writing was flawless upon my first reading, and I'm usually quick to pick up typos, grammar, spelling, and punctuation errors.  So many technical articles look like they were written by someone for whom English was a second language.

I might actually try to build this project myself. I might consider other materials than wood, e.g., Corian® or aluminum.  Hey, how about making a wood version for the first cut and using it to make a second version of itself for the Corian or aluminum version?

Nice use of an encoder. Good mathematics knowledge for a teenager.

Charles Murray
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Re: Impressive gadget
Charles Murray   10/18/2013 6:14:44 PM
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I agree, 78RPM. This author is an amazing inventor, regardless of age. His past inventions, an LED flashlight and LED lantern, were equally impressive. I agree with you -- he could have a great future in engineering, and the engineering profession would be glad to have him.

Rob Spiegel
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Re: Impressive gadget
Rob Spiegel   10/19/2013 5:23:12 PM
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Thanks for the comment, 78rpm. I'm sure John will apprecaite it. As for editing, John's submission required very little editing. This is one of the best Gadget Freak submissions by anybody, and I've seen them all from the start.

John Duffy
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Gold
Re: Impressive gadget
John Duffy   10/20/2013 3:07:04 PM
Thanks much, I appreciate all the positive feedback from this project.  Even though the  quality of technical writing was probably from somewhere between the design news editors and spellcheck, not any specific skill on my part. 

I would definately agree that a synthetic material or metal would make a much sturdier device, though as it is now, the mill itself would not be able to mill aluminum, or anything beyond hard woods with any accuracy or speed.  Plastics might work, but it would probably be better to use another mill designed for greater precision or strength, as this design was only used because it is very easy to make using only the tools in my schools woodshop.  Something smaller, and some type of linear bearings would probably keep everything from bending and turning as much as it does now.   

Thanks again,

John. 

rathomas
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Iron
Re: Impressive gadget
rathomas   10/21/2013 11:29:20 AM
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Good work, John.  I sent this link to my 13 year old son.  I think it's partly young folks like you (maybe you specifically, regarding LED flashlights:) making things like this that inspire my son to dabble in things mechanical and electrical.  He restored a 50+ year old industrial air compressor earlier this year and his most recent project involved rewinding the secondary of a toroid transformer to get the 36 Volts he needed to power a 50W LED module.

He made videos of that and more and put it in his YouTube channel.  Look for YT user XfmXz if you'd like to see what he's been up to.

I'm sure he's picked up an interest in tinkering from me, but I think seeing other teenagers doing cool stuff on their own inspires him and removes any reticence caused by the "I can't do that because I'm just a kid" kind of feeling.

Electron Wrangler
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Re: Impressive gadget
Electron Wrangler   11/20/2013 5:53:54 PM
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Well done, John.

For more stiffness, check out the "SuperStrut" at Home Depot.  They carry a limited range of stuff to bolt it together.
McMaster-Carr has a wide range of accessories.  Search there for Strut Channel.  Take a look and then go to your local Electrical Supply Wholesaler.

To see it in action, look up at any big box store.  It will be supporting conduit, refrigeration lines, and almost anything else they hang from the rafters.
The sturt isn't cheap, but it may be the least expensive way to get the stiffness you need.  Because of the accessories, it may be easier to put together than chunks of aluminum.  You could save on accessories by welding joints.

For the other old guys out there, using the strut is like a big-boy Erector Set.


Keep up the good work.

John Duffy
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Re: Impressive gadget
John Duffy   11/21/2013 4:52:21 PM
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I did look into a similar thing from menards, but I generally trying to avoid anything that requires tools beyond those avaliable at my school or home, because I can't use much beyond that. 

The big issue with this is in joints, the tool holder, "vise", and linear slides, not in the material itself. 

I do have another project with a gantry that that might be useful for, though. 

Jim S
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Accuracy
Jim S   10/21/2013 10:29:34 AM
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I'm sorry to rain on the parade, but commentors have confused resolution for accuracy. With the construction there is no way to achieve 0.001 accuracy on the X & Y axis'. It is not stiff enough. Perhaps the mechanism totally unloaded could achieve that accuracy, but a mill involves side loads on the tool and it's supports in order to perform the task. I am still impressed with the iniative of building it. It is no substitute for a Bridgeport.

John Duffy
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Gold
Re: Accuracy
John Duffy   10/21/2013 2:50:12 PM
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I see how it seemed that i meant this as a replacement, so I'm sorry for the misunderstanding. This really is not a replacement for a true mill so much as a way for people who cannot afford a well-constructed mill. In my other comment I mentioned making a smaller, sturdier mill as opposed to this design. This was made as it was for easy fabrication and building without accurate tools or strong materials. It was also designed for soft materials, and thus lower side loads. So yes, it will have a low accuracy if you try milling anything beyond soft wood at low speed, but that's really what it's made for.

Jim S
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Re: Accuracy
Jim S   10/21/2013 4:46:54 PM
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Great job. I just wanted to clarify the impression recieved from the introduction.Stiffness is the key to accurate machining. You will realize what I'm talking about after you've used it some. Keep up the good work.

John Duffy
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Gold
Re: Accuracy
John Duffy   10/21/2013 5:30:18 PM
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I've used it a bit, and noticed, especially at first, a lot of movement.  Originally, there were no steel rods, only the angle aluminum.  That did not work well, so I added the rods for support, though I hope to upgrade them to actual linear bearings (or at least brushings) and at larger diameter rod in any future version.  The stiffness of most of the device is okay, but the improvised vise and Z axis generate most of the looseness.  I do plan to make another version at some point that at least uses more precise parts and a better design, if not better materials.

Tool_maker
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Re: Accuracy
Tool_maker   10/22/2013 6:35:32 AM
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  This is a very interesting and clever bit of work which I could never invent. However, I do not think you would have to go to steel for the rigidity you seek. We regularly build fixtures from aluminum extrusions that are ridgid and stable. They come with T-slots for which you can purchase clamping components and accessories to built very complex frame works.

John Duffy
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Re: Accuracy
John Duffy   10/22/2013 11:27:29 AM
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I did originally look at using 8020 extrusion, as we use it frequently for prototypes on my robotics team. I only didn't use it because it is significantly more expensive, and has to be ordered either online or from places who usually sell huge orders o big companies, and will be unlikely to sell small quantities without significant markups. eBay and other auction sites sell it at a reasonable price, but it's still generally beyond the ~$7 I spent on steel rod and 2x4. I do plan to make some significant upgrades at some point, like using extrusion or linear bearings.

Tool_maker
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Re: Accuracy
Tool_maker   10/22/2013 12:53:17 PM
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  From seeing this and other things that you have posted, I should have realized that you would have thought of the extrusions. I am impressed by your knowledge and craftsmanship. Someday I am sure you will make a big mark on society. Well done.

John Duffy
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Gold
Re: Accuracy
John Duffy   10/22/2013 5:06:05 PM
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Thanks much.  I really hope so too, in that I will be able to benefit society, in any capacity, in a positive way.

William K.
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Re: Accuracy
William K.   10/24/2013 7:55:54 PM
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toolman, while improving the accuracy would be a challenge, and using aluminum extrusions would be one option, there does exist an alternative that I have heard about. It was used on some older Chinese machinery, which is making the framework out of good concrete, with steel inserts to accept the bolts and support the bearings. The equipment that my acquaintance had seen had probably been produced in the i900 to 1910 era, and it was still usable around the late 1930's.  A similar technique has been used for some machines made in the USA, although those machines had a much larger proportion of much better quality steel.  The other very real challenge to maintaining accuracy is the threaded rods, since that form of thread wears faster, and the normal threaded rod stock is quite ssoft steel.

I did not grasp where the arduino came into the picture, but it was  quite an interesting thing to see the claimed accuracy and then the video showing the wider cut due to vibration. Resolution does not equal accuracy or repeatability.

But the project does show a great deal of initiative and creativity, and a lot of determination.

A good source of the various extrusions would be industrial surplus houses and scrap dealers. These may also have complete assemblies available as well. And pricing is usually closer to the scrap value of the material than the new price.

John Duffy
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Gold
Re: Accuracy
John Duffy   10/25/2013 8:45:29 PM
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I did originally considder using concrete, as I read about that somewhere, though I believe it was actually used as recently as WWII for mills and lathes near the front, so they could quickly and cheaply make machines for repairing guns and the like.  I ended up not using it because it requires forming/molding, which would be significantly more difficult than just cutting some 2x4s.  I did considder that threaded rod is definately not the best option, a leadscrew designed for this obviously is.  The problem is, they're fairly expensive, and this was solely for the purpose of having something that requires no unusual/salvaged parts, and costs as little as possible. 

The accuracy is good, but only if the material is cut very, very slowly, though the precision is (as seen in the video) very good, even for a "real" mill.  The arduino is used to read rotary encoders on each axis, and display that information on a tv taped to the top of the mill.  That is why the mill is very precise, though that precision is compromised under any noticable side load.

 

William K.
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Re: Accuracy
William K.   10/27/2013 4:39:24 PM
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John, One handy source of acme threaded leadscrews is in automotive power seats.  For many years the for-aft screw has been several inches long. If you are able to weld pieces togather end to end that could be a reasonable choice, although the nuts nay be a bit loose, a preloaded pair could solve that problem as well. An added bene fit is that the motor drives are alredy assembled to the screws, at least in some cases. 

Of course the validity of this suggestion depends a lot on the price of used seat bases. 

Actually, some scrapyards may yield really useful treasures in the areas of parts. And adding recycling to the list of a projects values is always a positive thing.

John Duffy
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Gold
Re: Accuracy
John Duffy   10/27/2013 5:08:09 PM
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Actually, I've got two such motors from american science and surplus.  I was originally going to use them to drive the standard threaded rod (remove/cut off the leadscrew), but I found better motors since then, and I'm working on milling functions with those.  The leadscrews are only a few inches long, and I'm not sure if welding would yield a very straight or accurate leadscrew.  Plus, I don't have a welder.  With a precision jig, welder, lathe (there can't be any addition material from the weld in the screw itself) and a VERY straight saw, it might work, but in my case, threaded rod is really the only viable option. 

I do plan to use the motors with leadscrews, as you mentioned, for a smaller mill, probably a CNC for making circuit boards or something.  That requires a similar setup to the milling function motors, which I'm still working on.   

And while reusing things that would otherwise be thrown away (like the seat motors) is great, I often find that projects which call for something that's "easy to find at a local junkyard/surplus store/thrift store" rather annoying when its something rarely thrown away, or found at such stores.  For personal projects, I use these sorts of materials all the time, but when I put something online (here or on dedicated how-to sites), I try to use only materials avaliable retail, even if its slightly sub-optimal. 

William K.
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Re: Accuracy
William K.   10/27/2013 6:25:56 PM
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John, it is indeed a challenge to align the shaft pieces accurately enough. No question about that. That is where he concrete fixturing comes into play. The supporting surface is made using one longer section of angle stock, giving you a groove with 45 degree sides and perfectly aligned. The gap for working on them is formed with modeling clay, regular clay, wax, or somcthing else to provide clearance below the rod sections when the casting is turned with the goove up. Then it is just a matter of setting the rods so that there is no thread offset. That can be done with a scale or a nut or really good eyes. I recommend using a scale to set the end to end gap. And if not welding, then brazing, which is a lot more like soldering. And any excess simply gets filed away. Not a simple method, but fairly cheap and it does not require much in the line of expensive resources.

And you may be able to send out an apeal to the Design News readers for a contribution of some materials. Presently I don't have access to any, but 25 years ago I could have got you a two foot section of leadscrew that was only bent a little. It can be straightened with lots of patience, wood blocks, and a medium hammer.

John Duffy
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Re: Accuracy
John Duffy   10/27/2013 8:32:50 PM
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I do agree that it's possible, just way more difficult and time-consuming than it would be worth in this case.  With this design, other factors will compromise accuracy far more than threaded rod being worn down by nuts, or manufacturing tolerances in it.  It's far from perfect in either case, but just isn't a significant factor in this specific design.  I wouldn't want to ask the people reading this to contribute parts for projects, because for one, I get paid way too much for these in the first place, and if I end up not finishing a project or it's not approved by Design News, (though not finishing it is more likely, I have at least two bins of semi-abandoned projects at any given time). Also, I am waiting a little while to redesign or rebuild the mill, at least until my 3D printer gets here (a makibox), as that will allow better tolerances and more complicaed parts, though only small ones.    

Once make something more substantial, using the "right" materials otherwise, and with a stronger, more stable design, I will look more seriously into leadscrews and/or ballscrews.    

William K.
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Re: Accuracy
William K.   10/27/2013 10:03:17 PM
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Yes, there is always room for improvements after the proof of concept model is working. And it is easier to improve an existing design than to come up with a newer better one,

a.saji
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Silver
Re: Accuracy
a.saji   10/28/2013 12:45:07 AM
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@William: Yes in a way but I will not agree on that completely since it all depends on what the requirements is. If the requirement needs modifications and does not cost much, then its always good to edit the existing but if the requirement is huge and costly then should go for a new one indeed.  

John Duffy
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Gold
Re: Accuracy
John Duffy   10/28/2013 6:43:02 PM
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While I definately agree, that in most scenarios, it's better to remake something that already exists, as a.saji said, there are also many cases where it's better to totally remake something.  With this design, for example, the X axis has very little connection space to Y along the Y direction, which allows it to tilt easily, and mostly, the Z axis is  small, insecure, and can only hold light tools.  While it could be redesigned, it would be much faster and easier to compleatley remake it, from the ground up, based on what I learned from making this.  I have revised and redesigned quite a bit on this one already as well.  Originally, it used a triangle side, similar to a reprap, and an X axis that moved the Z.  Then, it was revised similar to the current version, but with no steel rods to act as guides, then a weird Z axis, and so on.  This revision gave me the best performance I could, with my time and resources, obtain from this general design. 

Cadman-LT
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Platinum
Re: Accuracy
Cadman-LT   11/14/2013 4:58:04 PM
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John, I think it's great. I wasn't aware that teenagers even knew about machining! Great job!

Cadman-LT
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Platinum
Re: Accuracy
Cadman-LT   11/14/2013 5:03:45 PM
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I actually made one a long time ago out of a drill press and a moveable/crank vise. No accuracy at all...but it does the job for crude work. A readout would help!

The Ticktock Man
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Iron
Re: Accuracy
The Ticktock Man   10/22/2013 2:23:20 AM
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Resolution DNE accuracy DNE precision.

Since this is actually CNC rather than human-skilled machining (in spite of the title), I can think of both computational and electronic corrections that could get at least CLOSE to that kind of precision (.001 with a wood frame would be nearly magical though, wouldn't it?). Feedback loops, appropriate sensors, and some skilled coding...

John Duffy, are you SURE you've not fallen through a wormhole from a '50's Heinlein or a '30's Campbell story line?

John Duffy
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Gold
Re: Accuracy
John Duffy   10/22/2013 11:15:01 AM
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I do agree that though the resolution and precision are fair, and the accuracy is what falls due to a lack of rigidity. I believe it would not be considered cnc, because though computerized and has a numerical readout, the actual operation is handled by a person. There are no steppers or servos other than the tool. Because the threaded rod produces a very strong an accurate motion, the precision is within a thousandth, though once a load is applied the accuray falls a bit. I'm also not entirely sure what you mean by a Campbell story line though...

bobjengr
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Platinum
BACK TO THE MANUAL MILL
bobjengr   11/20/2013 5:08:13 PM
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John--let me first congratulate you on your creativity then indicate I agree completely with your comments about the level of understanding relative to STEM subjects.  I run across individuals who seem to delight in telling everyone that engineering, manufacturing and particularly R&D work is for those who can't do anything else.  I have one lawyer "friend" who can't do much more than turn on a light switch yet he wants to save the world.  Your mill is an excellent example of creative engineering at its best.  Please keep up the passion for "invention"--it got us to the moon, and back. 

ltron
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Gold
Re: Accuracy
ltron   11/20/2013 7:15:14 PM
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1 saves

Great job John!

Your mill looks pretty good to me. A project like this offers many lessons. As you use it I am sure you will find new and interesting issues.

Don't jump to fault it too quickly. All mills have accuracy issues if not used with care and within their capabilities.

The lead error of your drill rod is more than likely pretty good. The greater issue may be wear. This is the main reason to use an Acme thread rather than a higher angle machine thread. A ball screw is even better but still has many similar limits.

As for backlash, you don't actually need to worry about this too much as long as you approach your tool position from the same direction all of the time. It's quite common to simply add moves to take up the backlash when necessary. Even with a good ball screw it can be a good practice.

Rigidity mainly effects how heavy of a cut you can take. For accuracy you can always take a number of lighter cuts as you reach your final position. This is true even with a very rigid machine. Remember that the part and tool holder deflect too. Much of the time this is the real limit.

Modern machine tools are actually much less rigid than their predecessors of many years ago. It was found better to simply take a greater number of lighter cuts rather than build the ultimate in rigidity. Sort of a speed vs. brawn thing. Well $$ had a lot to do with it too.

Sure your mill can be improved a lot but always remember the reality of diminishing returns.

Good Luck!

 

John Duffy
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Gold
Re: Accuracy
John Duffy   11/21/2013 5:22:51 PM
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I am aware of, and I do keep backlash compensation in mind.  I am not really concerned about wear, as I don't plan on using this specific one for a long time, I do plan to upgrade to a "real" mill soon. 

As for diminishing returns, that's actually how I generally gauge how interrested I *really* am in a project, if I finish a revision, then don't spontaneously start redesigning and rebuilding bits of it, I'm generally not very interrested.  Many projects, however, which I do improve are generally just as rewarding to improve as to make in the first place. 

Thanks much. 

mrdon
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Platinum
Re: Accuracy
mrdon   11/21/2013 8:23:36 PM
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John,

Great video and project. I'll be showing this video to my electronic students to inspire and motivate them to build their projects for submission to the Design News Gadget Freak column. Just curious, where do you get inspiration for your projects?

John Duffy
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Gold
Re: Accuracy
John Duffy   11/21/2013 11:25:49 PM
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Thanks, and I usually get ideas either from seeing something someone else did.  For my first gadget freak, the wireless lanterns, I got the idea from MAKE magazine, when I saw the project, I thought that the lanterns were glued shut, so I thought of how they might be recharged without opening them.  The other two were for the object that I actually made, not just as a proof of concept.  The really big lantern was made because I go to a summer camp for Boy Scouts, and we have to use tiny flashlights or propane lanterns for light.  This one was because I use mills at robotics, and thought it would be really useful to have one at home for personal projects.  If you mean the method by which I make them, it is all just looking online and through the few issues of popular science and MAKE that I have, for designs and components for similar functions (the joule theif from a MAKE video for the lanterns, a CPU cooler for the other light).  For this, I looked up many methods of determining distance for the DRO before settling on encoders, and many displays before settling on the TV, and even several different microcontrollers before going with the arduino (my first thought was a teensy, as they are cheaper and smaller, but I had an extra arduino already). 

mrdon
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Platinum
Re: Accuracy
mrdon   11/21/2013 11:42:16 PM
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John

I like your approach to developing PoCs (Proof of Concepts) by researching what already exists and doing a remix to solve a specific problem. Re-purposing what's available in one's junk box or lab is definitely a good method of reducing development cost and expediting the PoC build. I enjoy your Gadget Freak videos and look forward to seeing more of them in near future. Keep the vision alive and clear as well as the Product Development projects.



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