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16  Forum 2005-2010 (read only) / Interfacing / Re: Making an eternal pendulum on: September 21, 2007, 07:23:02 pm
If you go ahead and use sensors to sense direction and/or speed and a controller, you could probably do with just one "kicker"
17  Forum 2005-2010 (read only) / Interfacing / Re: Making an eternal pendulum on: September 21, 2007, 01:24:28 pm
Unless you're very lucky in your scrounging of surplus materials, you'll probably have to wind the coil yourself, but the specs don't seem to need to be precise. Some enamel coated magnet wire and a low speed power drill would probably make it go much faster - just remember to add the center tap. You can Google around for tips on winding electromagnet coils and solenoids and I'm sure there are some good and easy ways.

Remember that the "kick" this device imparts on the pendulum doesn't have to be very large as a massy pendulum loses momentum slowly (a ball bearing on the top would help and you can rip them out of skateboard or roller blade wheels), but the kick does need to be in the proper plane of motion, so I don't think it would work behind the pendulum mass. I was thinking that it should be at the bottom of the swing, but I'm not sure if the effect would be canceled out by the reciprocal motion.  Maybe you could use two kickers and angles and set to alternately pause so that each only kicks in one direction.

Let us (or at least me) know what you find out!
18  Forum 2005-2010 (read only) / Interfacing / Re: Making an eternal pendulum on: September 21, 2007, 09:18:35 am
This may not be as fun as a full blown microcontroller based project, but you might be able to use something like this if you could tune it precisely enough: (this is a really cool site, BTW)

It is a hand wound, iron core coil, a transistor, and a battery. When a magnet swings by, the induced current in the center tapped coil generates a pulse that briefly turns on the transistor, energizing the coil from the battery, and providing a magnetic "kick". When there is no motion, the current drain on the battery is near zero.

If your pendulum arm has a magnet on the end, you should be able to orient the kicker to give it a steady perpetual motion. Best of all, the kicker can be hidden so there is no obvious motor or drive mechanism for the pendulum.

If you are really set on using the Arduino or if tuning the motion seems difficult, you could use sensors (optical or Hall effect come to mind) to provide feedback to the controller and then adjust the kick of the coil.

Note that these "kicking" effects would slightly alter the regular pendulum motion. You could also use an escapement mechanism like those on pendulum clocks. Instead of spring or weight, you could use a motor or solenoid.

Sounds interesting either way...
19  Forum 2005-2010 (read only) / Interfacing / Re: Basic Electronics Questions - Toggling I/O on: September 24, 2007, 07:25:51 pm
Yeah, I think that is what I was looking for. Thanks! I'll scratch my head over it a bit and give it a try on my Arduino.

Does this involve any of those tricks like reading inputs from output pins or whatever that is where you are engaging and disengaging the internal pull up/down resistors?
20  Forum 2005-2010 (read only) / Interfacing / Basic Electronics Questions - Toggling I/O on: September 24, 2007, 06:59:25 pm
This is a pretty easy question, but I always get confused about pull ups and pull downs and stuff...

Imagine a simple ring-in "game buzzer" type setup (it's a close as I can describe it). Of course if I set a pin to input and put a switch on it and set another pin to output and put an LED on it, then I can check the state of the switch and turn the LED on and handle lock-out and stuff with code.

If you have more players than you have pins, you could use mux/demux and other digital logic. I understand that and those chips are cheap, but that isn't my question either  :smiley

What if you wanted to have each pin handle the input and output, how would you wire it up and code it so that the loop() function scanned the pins set to input and when a button is pressed connected to an input pin, that pin could be set to output and light an LED on that pin (no other inputs would be considered until a reset button was pressed)?

Consider a simple case using two pins and a minimum number of components (pushbutton switch, LED, current limiting resistor). Can that be done? Can you connect a reverse biased LED in parallel with the switch or something?
21  Forum 2005-2010 (read only) / Interfacing / Re: Interfacing with FPU on: September 20, 2007, 11:46:41 pm
The instruction set on the FPU looks intriguing, plus it will nearly automate much of GPS communication and decoding, which will free up the Arduino for handling several other tasks. I was fairly worried about splitting up the time of reading the NMEA data and doing some other I2C and I/O at the same time, but this might do the trick.

Plus it should be much faster...
22  Forum 2005-2010 (read only) / Interfacing / Interfacing with FPU on: September 20, 2007, 04:45:56 pm
Has anyone tried interfacing their Arduino with one of these?:

It's a floating point co-processor made for microntrollers with I2C, SPI, and plain old serial inputs. Essentially you pass the code for the FPU during the setup process then call it by sending serial and receiving serial data.

I've got one on the way, so I'll be happy to be the first guinea pig, but I would appreciate any info up front.

I really got it because I am working on a GPS project with the Arduino and the lack of floating point arithmetic was going to be a big coding problem. Not only does this FPU do the floating point, but it also has it's own external serial interface and it can read serial NMEA data straight from a GPS or GPS module and has well documented functions for the string operations to dissect the NMEA output and a lot of references on DMS to decimal degrees to radians, great circle distance and bearing calculations, and a lot more. I'm just hoping I can get it working - I may be asking a lot of questions here on the forums.  :o

Manufacturer Info:
23  Forum 2005-2010 (read only) / Exhibition / Re: Wii Nunchuck Tilt and Stick Control of Two Ser on: December 14, 2007, 04:14:17 pm
Very cool. I just did basically the same thing. I build a small web-cam gimbal using two servos and use the Nunchuk to point the camera. I would like to see your code, too (I'll post mine and a video when I get a chance to (a) take the video, and (b) clean up the code). Your movement seems just a little smoother than mine and I'd like to compare notes on how you did your averaging...
24  Forum 2005-2010 (read only) / Exhibition / Optical Tachometer on: September 20, 2007, 04:16:20 pm
A long time I ago I put up the Beakman's Motor Page ( When I got my Arduino Diecimila, I decided to make an optical tachometer to measure the speed of these simple motors. I did this to both teach myself a little about Arduino development and because I get asked repeatedly how to measure the speed. This may not be the simplest way, but at least it works and I have something to tell someone when they ask.

The project is up on Instructables:

More pictures at:
25  Forum 2005-2010 (read only) / News / Sparkfun Arduino Skinny on: May 29, 2008, 04:07:42 pm

They just showed up on the new products blog, but they're sold out (or not in stock yet). Thoughts and opinions? Anyone tested one of these yet?
26  Forum 2005-2010 (read only) / News / Re: Interesting kit's - cheap on: January 28, 2008, 11:07:52 am
But are we still talking "per item" or is the shipping a flat rate up to certain weight/number of items?
27  Forum 2005-2010 (read only) / News / Re: Interesting kit's - cheap on: January 25, 2008, 02:53:50 pm
To save me from having to fill out a sample order and then cancel it, does anyone know: (a) if "courier" is the only shipment method to the United States, and (b) if the rate is around $25US, is that per item or how the shipping breaks down for multiple items?

It might be worth getting together group orders. The prices are great otherwise and I do have a friend who is living in India currently - I wonder how much room he has in his suitcases?
28  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: What software do you use to draw circuit diagr on: February 14, 2008, 10:20:17 am
I think you're right, but I was having a good time trying out all of the packages on this thread and they led me to KiCAD.

For breadboard layouts, I've been trying (with varying degrees of success) to use Visio. I've created template libraries for all of my breadboards, Arduinos, shields, and a few common parts. I find myself fighting it as much as using it, though. The smart connector routing is the biggest pain, but at least you can layout the major pieces, print it out, then use pencil or pen to play around with the wiring. I'll eventually get the rules right, I suppose.

I haven't tried the Open Office Draw in a while, so that will go on my ToDo list as well...
29  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: What software do you use to draw circuit diagr on: February 13, 2008, 07:38:24 pm
I just downloaded KiCAD and it looks full featured and promising (but a little complex). It's open source (GPL) with source and binaries for Windows and Linux. It has schematic drawing, netlist generation, and PCB layout all integrated.
30  Forum 2005-2010 (read only) / Bar Sport / Re: How do you deal with your destruction? on: January 22, 2008, 11:31:23 am
The trap that a lot of garage inventors fall into is the idea that they have an absolutely original idea that will make them millionaires and that they must protect their idea and develop it in secret because otherwise it will be stolen immediately and exploited (or suppressed) by evil large corporations.

The sobering historical reality is that there are very few absolutely original inventions. Newton's comment about "standing on the shoulders of giants" is very apt, since most inventions and discoveries are incremental and evolutionary rather than revolutionary. I've also decided that there is a certain inevitability about some discoveries and inventions - once the right mix of foundational technologies exist and the right ideas are floating around, certain new applications and combinations of them are almost inevitable and simultaneous independent invention is likely. Many ideas I've come up with are like that - I come up with ideas that are original to me, but with a little research, I find that it's already been done or that someone else has just announced they are working on the same idea. You just have to deal with that as a reality and keep trying.

The second part of the trap is finding that the idea has been explored before, but was never realized into a product or that it was realized into a product, but went nowhere. There are many causes for this. Sometimes the idea sounds valid, but turns out to be impossible (e.g., free energy, perpetual motion, or inertia-less propulsion), sometimes the idea and product works perfectly, but the market just isn't there - either the target market is too small, it doesn't appeal to many for some reason (fashion, culture, etc.). Sometimes the idea was implemented badly causing the market to reject it. In some cases, this is a great opportunity to improve it. In other cases, public reaction was so bad that the market will reject similar items for a long time. Look at how long it took PDAs to become accepted and all of the backlash that early models received.

Take, as an example, this Arduino forum. You read one post on one of the subgroups where someone does something cool. Then you read another unrelated thread where someone else is doing something cool. Then you get a bright idea - "I can combine aspects of both of those ideas into a single gadget!" Congratulations, you just had a totally original idea for an invention. Unfortunately, chances are, dozens of other readers also just had the same original idea. Even then, all of you are a long, long way from a marketable product.

So, for 99% of ideas for inventions, you need to be honest with yourself and be willing to let go of ideas. Often, design, fashion, and usability are as, or more, important than functionality. Look at the iPod, iPhone and other Apple products as an example. Each of these devices offer only incremental technological innovation, but their ease-of-use, "cool factors", and design elements make them a hit. Read books on design, such as "The Design of Everyday Things" or "The Evolution of Useful Objects" for a better understanding of how design is as important as innovation and how having the groundbreakingly original idea doesn't always mean you win the market - it may be the 5th evolutionary generation of an idea that hits it big.

Finally, as others have said very well, if you are still convinced that you have an original idea that you feel is marketable, you still have a lot of work to do. Business plans, multiple prototypes, usability testing, market research, pitches, and so on. You don't want the first investor you approach to say, "I had something like that ten years ago and I hated it!" If something similar was available then, you have to be prepared to explain why you have fixed all of the problems and have a plan for telling the market why your idea is better. If it is completely revolutionary, you may have to build the demand through marketing - remember that there was a time when people didn't think they would ever want or need a cell phone, for example.
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