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16  Topics / Robotics / Re: Ball detection + driving towards the ball.. on: August 17, 2012, 10:01:37 pm
A smartphone (Android or iPhone) with a camera would be a good choice.

I couldn't figure out why the ball was getting bigger...Then it hit me!
17  Topics / Robotics / Re: Video camera with arduino + image processing. on: August 17, 2012, 09:56:02 pm
Use a smartphone. If you don't have one, ask friends and family for an old one. It does not require phone call capability which is why an old phone is ideal. Smartphones support openCV which you could then play with for hours. I'd also recommend you send the images to a PC for R&D. It is a better practice to work with image processing on a PC with OpenCV, Octave or MatLab. Once you figure out what you are doing, then recode it on a smartphone. OpenCv on a PC is better is because it is funner. You are more likely to get it working and have fun doing it.
18  Using Arduino / Project Guidance / Re: VEX and DF RobotShop Rover verse homemade bots on: August 17, 2012, 09:43:55 pm
R/C kits are a good idea. I had a Tamiya Grasshopper that is much quicker and better made than similarly priced robots. I guess I've been resistent to using toys. I only went with tracks after similarly powered three wheeled robots got stuck climbing from floor to rug.
19  Using Arduino / Project Guidance / VEX and DF RobotShop Rover verse homemade bots on: August 14, 2012, 03:40:23 pm
Any opinion on VEX and DF RobotShop Rover 2 verse homemade bots?

Though I enjoyed building a robot, I've come to the conclusion that my tracked device, which is very similar to a DF RobotShop Rover 2, is a piece of garbage. The tracks derail and it is hard to change the batteries.

I was considering just buying the DF RobotShop Rover 2 with XBee/ethernet option or buy the VEX starter bundle for creating a proper frame. Or maybe its time to buy something better/more expensive? My main interests are machine learning. It is convenient to have a shoe box sized robot that is easy to transport.

DF RobotShop Rover 2:

20  Topics / Robotics / Re: Controlling Robot Using cellphone on: August 14, 2012, 03:21:09 pm
Can you just connect the arduino to the cell phone's audio jack, like when listening to a phone call with ear plugs? The Arduino would have to decode the frequencies of the tones.

While decoding a phone call's tones is cool, you could just write an app for your phone that connects over the internet to your server or the Arduino could connect directly with the server (over bluetooth or wifi.) This is pretty normal stuff.
21  Topics / Robotics / Re: Video camera with arduino + image processing. on: August 14, 2012, 03:08:36 pm
Might you give some idea what your application is? It would expand the discussion.
22  Using Arduino / Motors, Mechanics, and Power / Re: AA verse LiPo Batteries on: August 14, 2012, 03:02:11 pm
I was trying to put an order together for SparkFun, but can only find one two-cell charger that people say sucks. Has anyone bought a good two-cell charger from them or is it time to look elsewhere?

SparkFun carries 2000mAh Polymer Lithium Ion Batteries for the motors. This would work for the Arduino:

It is expensive. 1 charger ($33), 1 motor battery ($17), 1 spare motor battery ($17), 1 arduino batter ($7) and 1 spare arduino battery ($7) costs around $81+s/h. Assuming I can find a good charger, I hope it cuts down on the weight and works smoothly. My tracked robot was kind of crappy, so just replaced some cardboard sides with HPDE. The AA battery packs did not fit well in the frame, so hoping these would fit better and be easier to change.

23  Using Arduino / Motors, Mechanics, and Power / AA verse LiPo Batteries on: August 12, 2012, 12:22:13 pm
I have a 5V Arduino and 3V motors. They are powered by separate 4 AA battery packs. The battery packs are quite bulky and heavy. Would LiPo help?

Separate battery packs are used to prevent interference and because the motor drains much faster than the Arduino. These are the motors:

AA alkaline capacity is ~2000mAh per battery.

LiPo capacity 1000mAh 7.4V

A 4 AA battery pack would be equivalent to 8 LiPos. I guess you could put 4 LiPos in the Robot while the other are charging. I guess 1 or 2 2-cell LiPos would could power the Arduino for a fairly long time, but the motor would need 4 single cell batteries.

This sounds like a modest weight savings.

Is this right?  Is it worth converting to a 3.3 V Arduino as 3.3V devices like the motors require single cell batteries?

24  Using Arduino / Programming Questions / Re: Motor interacting with ultrasonic motion sensor code problems. Please help! on: August 11, 2012, 09:23:33 pm
You are correct in your diagnoses. The trick is that the Arduino supports PWM. This means that you set a pin to a level and you are done. There is no need to worry about the timing within your main loop. 

Read about an Arduino library for this here:

And just google "PWM" for a wikipedia article that describes it well.
25  Using Arduino / Programming Questions / Re: An error... on: August 11, 2012, 09:07:53 pm
You fixed it, nice job!
26  Topics / Science and Measurement / Re: Playing with FFT on: August 11, 2012, 09:59:00 am
Is this for making an FM transmitter? What is FFT used for?
27  Topics / Robotics / Re: Starting my first UGV project - need some starting help on: August 11, 2012, 09:54:51 am
Did you ever get video to work? What did you use?
28  Using Arduino / Programming Questions / Re: An error... on: August 11, 2012, 09:29:32 am
Cleanup the formatting in HandleStoppedState(). You may have an extra end brace. Or you may have done something like (} instead of ().
29  Using Arduino / Programming Questions / Re: An error... on: August 11, 2012, 09:27:02 am
Oh, I thought you got past the compile issue. What does it mean "replace serial with cell"?

When you get a brace error like you have look at the brace right there and the function definition, and then look at what came before. There may be an extra or missing brace before this method.

Can you make your edits one step at a time and compile after each edit? When I work, I generally save a version of a sketch every few hours at a good stop point like when it is all working. Then I add a new feature in the next version. I might have Ignition1.pde, Ignition2.pde, etc. If a bunch of edits don't work out, I can fall back on yesterday's save point.

The other thing you might try is, in a copy like IgnitionTest1.pde, delete all the subroutines on the bottom and comment out their calls in the main loop. See if it compiles. After you figure out what was wrong, just go back to the original code and fix it.

And try Paul's suggestion to Auto Format the code. These errors are often missing braces that are hard to see when the tabs are wrong.

30  Using Arduino / Programming Questions / Re: Problems with IR Remote on: August 11, 2012, 09:09:35 am
This stuff is actually fairly hard, certainly not easy. You have modulation with your signal over it. You need some way to see what is being generated as well as an understanding of the encoding.

It sounds like you don't actually have anything working but occasionally an LED blinks which may mean the code is being decoded right.

Two things that could help are looking at the signal and using a library (like Ken's). These are both challenging and you will learn a great deal. So I am suggesting Ken's library again. You can start straight with the library and do the visualization after.
With Ken's library, guess at the common protocols with your device. Right a sketch to receive. Aim you remote and see if it works. Work through the common protocols until you find one that works. This will also tell you the key mapping, like what key is generated when you press stop. Then you write a sketch using the library to send the signals. (If you done have an IR receiver, you can just try sending signals.)

Ken's site has lots of info on IR and you can look at the protocols.

Another thing you can do is look at the signal from your remote control. There are sketches posted on this site for this:
. This will record a bunch of levels that would then have to be plotted. Once plotted, you can figure out the encoding. THis requires reading about the common formats. There are links on Ken's site. This step is fairly hard.

Plotting the IR output of your code would be a good way to debug your code. But it is probably better to start with the library. You will learn a lot by using it which will help you with your own code.

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