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16  Using Arduino / Project Guidance / Re: A robot able to play poker on: October 31, 2013, 07:39:22 am
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An Arduino plus a voice shield can be used to perform actions based on voice commands.

That is interesting, I was not aware of that. Will try and remember for future reference, it sounds like fun.
17  Using Arduino / Project Guidance / Re: A robot able to play poker on: October 30, 2013, 11:16:02 am
An Arduino is not suited to image and voice recognition.
You might be better to consider using a PC for those functions and interfacing it to a robotic arm to handle the chips and cards.
18  Using Arduino / Programming Questions / Re: Trying to understand given code errors. on: October 29, 2013, 11:30:30 am
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I created the code from scratch. This is my first term taking a robotics class

Compilers tell you where and what the errors are though it does take a while to learn how to understand the messages.

What you have done is write quite a bit of code then thow it into the compiler. Not surprisingly it had quite a few errors. Once you correct those and get the code to compile you are going to hope that it works, but it probably will not.

A better way to work is to start very simple. Write something that compiles and works correctly - just the famous "hello world" program for example. Then gradually add functionality to your program compiling and running as you go. If your program suddenly had problems compiling or stops working correctly you will know exactly what you did that caused the problem.
19  Using Arduino / Project Guidance / Re: Item count/number input on: October 29, 2013, 11:18:52 am
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The box normally has them all in numerically

How are you going to detect if the numbers are not sequential?
Even if they are sequential how will you know what the number of the "first" canister in a box is?
Those photographs show a weight, don't you have to include that in the paperwork?
What exactly do you mean by "Count out the number of cans I tell it I need"?

You might be better to tackle the root of the problem and get your supplier to provide canisters with barcodes and delivery notes in electronic format.
20  Community / Bar Sport / Re: why do leaves reflect green light? on: October 29, 2013, 10:52:36 am
Of course being geeks and not in touch with the soil we are overlooking the fact that some plant have leaves that are red/purple and other colors.

Perhaps those plants have adapted to living in the shade of their green cousins and make do with less preferable wavelengths?
21  Using Arduino / Programming Questions / Re: password checker 'Brute Force' on: October 29, 2013, 10:42:11 am
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i was going to see about using this to crack my wifi password when ever i buy the shield because im thinking thats how i got hacked anyway

Your wifi probably broadcasts the wirless network name (the SSID). Turn SSID broadcasting off, in most cases people will not even see your network and those that know it is there will probably not bother to try to hack you on the basis that;
  • Not only do they have to get your password they have to find the SSID
  • If you know enough to turn off the SSID your password is likely to be a pain, you will have firewalls etc.

The only downside of not broadcasting a SSID is that when you want to attach devices to the network they will not automatically "see" the network you will explicitly have to enter its name.
22  Using Arduino / Project Guidance / Re: Pulling a rope up and down with small weight on: October 27, 2013, 09:23:23 am
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Steppers okay but you cannot reliably use the step count as a position indicator

I disagree. If the stepper is properly sized for the load then step counting provides accurate reproducible positioning. As well as avoiding the need for position encoders it will also hold the load when static (though it will be consuming power) negating the need for a braking system.
23  Using Arduino / Project Guidance / Re: use arduino to help my daughter on: October 27, 2013, 09:13:46 am
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I suppose I'll start it off simple
That is always the way to go. If you have difficulties post your code and I am sure people will help out. If the film of your daughter is typical (i.e. not exaggerated for the camera) then I am fairly sure a tilt switch will do the job.  I cannot promise to keep up as I have a lot on at the moment but I have ordered a tilt switch myself to mess around with.

Although I have not taken to wearing high heels I have been walking around on tip-toe in different footware. Once I get to boots with ankle support and a steel insole it is not possible. Would a second prong of attack on the problem not be to get your daughter shoes/boots that have very firm soles? Then rather than having to remember not to walk on tip-toe she would have to make an effort to do it. In winter solid shoes/boots would not look out of place.
24  Using Arduino / Project Guidance / Re: use arduino to help my daughter on: October 25, 2013, 06:58:56 am
Mike, sorry I had not realised that you had already refreneced a force sensor.

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This force sensor is very flat
https://www.sparkfun.com/products/9375

I would still put my money on either the sensors or the switches because I think there is a better chance of being able to make something small that might not need an Arduino.
25  Using Arduino / Project Guidance / Re: use arduino to help my daughter on: October 25, 2013, 03:34:21 am
The objections from Grumpy_Mike and Paul__B to the tilt switch solution are based on the view that the signal from the switch may bounce around too much to give meaningful data.

I admit I am unsure how a tilt switch would perform in this application, but looking at the video I still feel it would work. Basically I think we are in a suck-it-and-see situation and a lot might depend on the actual switch selected.

How about this "change-over make before break" tilt switch?
http://docs-europe.electrocomponents.com/webdocs/107c/0900766b8107c8be.pdf
It might permit easy removal of a lot of spurious vibration contact breaks.

Mike you also mentioned "Force Sensors" do you have any specific devices in mind that might be suitable?

Does everyboy agree that;
  • Zero false positives are requred?
  • A high rate of false negatives, say 75%, is desirable?

26  Using Arduino / Programming Questions / Re: password checker 'Brute Force' on: October 24, 2013, 05:42:17 am
Brute Force and Dictionary attacks attempt to create a password that generates the same hash as your actual password.

Rainbow Tables work in reverse. They look at the hash and then attempt to generate a password.

This link gives good background;
http://en.wikipedia.org/wiki/Rainbow_table

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how do i check what hash is created by my password??
Don't worry about that, just make your password strong.
To make it strong don't use words or names.
Do make it long, mix upper and lower case and include digits and other special characters.

That of course makes it difficult to remember your password!

To get round that a good strategy is to use a phrase that you can remember easily then change and add characters. For example you might use a line of poetry, a book title, or a film title.
e.g. you might start with "Autumn season of mist" and create the password "Autumn_5ea50n_0f_m15t#"

Another strategy is to hide your password in plain view, for example "emw122AE!!" is my monitor model written backwards with a couple of exclamations on the end. It cannot be cracked by a Dictionary attack as it is not word based, and it would be difficult to Brute Force because it a resonably long alphanumeric with upper and lower case and special characters. At the same time I could easily remember it because it is more or less written right in front of me.

Do not use the same password on several sites. A site owner may well be able to see your password in plaintext. Once somebody knows your password for one site they will try it on others e.g. gmail, twitter, facebook.

Identity theft is a bit different from getting your password. Keep your personal information private. You can give madeup info to sites as long as you keep a record of what you gave  smiley-evil


27  Using Arduino / Project Guidance / Re: use arduino to help my daughter on: October 24, 2013, 04:42:57 am
My own reservation is that tilt switches work well in smooth mechanical systems but I am unsure how they will behave with the relatively chaotic three dimensional movement of a foot. However a test would be so easy that it seems worth a go.

I was hoping to avoid mercury switches as I see closures due to erratic foot movement as more of a problem than failures to close.

My thought is that an ideal system would generate no false positives and might have a false negative rate of perhaps 75% i.e. the child only gets warned about 1 in 4 times the behaviour occurs. A high false negative rate seems like a good thing to me as otherwise the child might become dependent on the device and not learn self control.

Maybe the solution will boil down to a battery, tilt switch, timer and motor (i.e. no Arduino). Thought that would still leave the serious problem of how to fit it in a shoe.

What are your doubts about the tilt switch idea Mike?
28  Using Arduino / Project Guidance / Re: use arduino to help my daughter on: October 23, 2013, 02:07:36 pm
I would be a bit wary about making your daughter overly self conscious about her problem, with a bit of luck it might be something she simply grows out of.

I see what you are saying about the movement of the red dot, but I don't think you are appreciating the complexity of accurately detecting that motion amongst all the varied movements kids make.

On the other hand by looking at foot movement the problem appears to become quite simple. The ball of the foot always makes ground contact, the heel never touches and the foot angle looks almost constant throughout the step.

The force sensor idea would almost certainly be workable, but you need two one at the ball of the foot and one at the heel. Having seen the video though I really think you should experiment with tilt switches.

I don't know how well tilt switches will work in this application but they are cheap and experimentation would be easy; Glue one to one of your  old shoes wire it up to your Arduino with a couple of leds. Light one led whenever the switch closes, write a sketch with logic to light the other led whenever it "thinks" problem walking is occurring. Walk around with the shoe on doing different activities and see how well your logic works and iterate the design based on the results. Try shaking your foot to see what the switch does, try lying on the floor.

Aim to write code that never gives false positives even if the false negative rate is very high.

My first attempt at logic would simply be to see if the foot is being kept above a certain angle for beyond a certain length of time i.e. foot held above 50deg for more than 10s then light led.
29  Using Arduino / Programming Questions / Re: password checker 'Brute Force' on: October 23, 2013, 01:28:22 pm
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Also any decent server should have some form of delay
Delays certainly make sense to protect the front door. However a lot of password hacking would be done by getting hold of the password file which might be accessible from an account to which the hacker already has access. Once that file has been obtained the hacker can then use brute force to try and find a string that generates the hash of other accounts such as the Administrator. Armed with a string that generates the same hash as the Administrator password (note the string and the password need not be the same) the hacker can then use the string at the front door and the delay offers no protection.
30  Using Arduino / Programming Questions / Re: password checker 'Brute Force' on: October 23, 2013, 10:31:16 am
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im trying to "see how secure my passwords are"

You would be better to look at existing password crackers.
In most cases the hacker does not have to find the exact password he only has to find a password that generates the same hash as your actual password.

As passwords are often words, perhaps with numbers substituting for some characters, cracking is often done by pre-generating hashes for words from dictionaries. Those hashes are then compared with the hash of the real password. You should also lookup Rainbow Tables which are not dictionary based.

 
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