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76  Using Arduino / Programming Questions / Re: Translation the shaft encoder data on: August 10, 2014, 09:09:11 pm
The encoder will enable you to determine how many times each wheel has turned.  That's all.

If your wheeled robot is going in a straight line,  and the wheels are not slipping on the floor,   then each complete rotation of the wheel will become a movement across the floor,  equal to the circumference of the wheel.

If the wheels are turning with different speeds,  or even in opposite directions,   then the robot will turn.  And in addition to turning,   the relationship between wheel turns and distance travelled will break down. 

If you run the left wheels forward and the right wheels backwards,   the robot will turn to the right.   It might go forwards and turning right,   like a car would,     or it may turn "on the spot",  like a tank or a shopping trolley can turn.   Without very detailed analysis of the geometry of the vehicle and the friction characteristics of the tyres,  it is almost impossible to model either in a general way or a specific scenario,    without making a lot of heroically over-simplified assumptions.

I think that your objective is unrealistic.

There is no "formula"  that will do what you seek.

I suggest that you build your robot,  and then carry out a series of experiments where you measure the path response to various speed and steering inputs,    and then you can develop some kind of empirical predictive model based on the results of those experiments and assuming that the robot's future behaviour won't change.
And, unless the robot is a balancing one, there will have to be a third point of contact. The position of this third point of contact, with respect to the wheels, and its construction/friction, will have a great effect on how the robot moves when the wheels are turned.
77  Using Arduino / Programming Questions / Re: program is not working after few hours until reset on: August 10, 2014, 08:54:30 pm
I have done a program for turn on relay using external interrupt input signal of another relay. When pregame is running it works properly. But after few hours gone and give again interrupt input, output relay is not turn on. how ever after reset then again program work correctly.   : smiley-sad smiley-sad smiley-sad smiley-sad

so can anyone tell me that what reason for that and please help me to clear that fault.
Sorry, but my crystal ball has crashed and I'm unable to read your code.

Note to self...Upgrade to a Windows 8.1 crystal ball urgently.
78  Using Arduino / Programming Questions / Re: What else can use unmolested Uno scripts? on: August 10, 2014, 08:26:54 pm
If I decide to go to a MEGA, what all is involved in changing the coding?  Say, for a clock as an example?  Just the basic readers digest version, please  smiley
The only difference I found between the Mega and Uno is that the analog pins (A0 - A5) on the Uno can be addressed as pins 14 - 19, but on the Mega have different numbers. You can still address them as A0 - A5 on the Mega, but not as 14 - 19. Apart from that, I've found no difficulty in moving sketches from the Uno to Mega.
79  Using Arduino / Programming Questions / Re: paralax range finder and blink without delay on: August 10, 2014, 08:04:27 pm
Feel free to analyze the rest of the code and give any advice you think might help.
All variables associated with millis() should be unsigned longs. It makes them able to hold numbers twice as big!
  if(ledState == LOW)
     ledState = HIGH;
     ledState = LOW;
can be reduced to:
ledState = !ledState;  //inversion
80  Using Arduino / Project Guidance / Re: connecting servo to motor shield on: August 10, 2014, 07:48:42 pm
Hi everyone recently got adafruit motor shield v1.0 and was wondering how i go about connecting the servo as nothing seems to be wroking?
You appear to be trying to run your servo from the  Arduino power supply. You haven't stated what type of servo you're using, but usually a servo requires more current than the Arduino can supply. I suggest you use an external supply for both your motors and the servo.
N.B. The Adafruit motor shield V1  has the servo numbers reversed on the silkscreen.
81  Using Arduino / Project Guidance / Re: Arduino fire alarm notification on: August 10, 2014, 07:33:28 pm
Do you see any major problems with my idea?
Yes. What if your Arduino catches fire?   smiley-mr-green
82  Using Arduino / Project Guidance / Re: Detect liquid on steel plate on: August 10, 2014, 07:21:25 pm
What technique would you use to detect how large area of a steel plate is covered by ketchup or a similar liquid? Is capacitive sensor appropriate?
If you know the temperature of the plate and the density, viscosity and surface tension of the liquid at that temperature, all you need to measure is the extra weight that's added to the plate by the liquid. You can then use the density to work out the volume of the liquid and the viscosity and surface tension to calculate its spread over time. All this assumes that the plate is dead level and that the liquid is applied to the plate in only one place.

Or you could just use a squeegee to spread the ketchup evenly over the plate for 100% coverage....

83  Using Arduino / General Electronics / Re: Gauging Interest: Printed Circuits on Paper on: August 09, 2014, 09:11:12 pm
Just what I said in reply #25.
Sorry Mike. I replied to the question before reading all the way down.
But I did put the answer in different terms to yours so that, between the two of us, he might 'get it'.
84  Using Arduino / Project Guidance / Re: Micro Infrared Bar Code Scanner on: August 09, 2014, 07:59:57 pm
Invisible IR Ink, I think you mean IR reflective.
I think he also means that it cannot be seen in the visible spectrum. I don't know of such an ink. There are UV 'invisible' inks that are used to mark property.
85  Using Arduino / Project Guidance / Re: LilyPad Jacket on: August 09, 2014, 07:46:03 pm
I am new to Arduino and don't know much about the controller in general.
I want to use the lily pad to make a led jacket that will have different led patterns depending on the bottom pressed.
That could get you arrested.  smiley
86  Community / Bar Sport / Re: Solder/Sodder on: August 08, 2014, 10:45:59 pm
Yes I "discovered" this a few years back and was told that solder has a silent L.

I suppose it is just like Ptolemy, that has a silent Pee, as in bath.
Silent Pees are quite common, as in Psyche, Pneumatic, Pneumonia and the sea, but I don't know of any English words with a silent L.
But, as Mr. Featherstonhaugh* would say, "Who are we to argue?"   smiley-grin

* pronounced 'Fanshawe'.
87  Community / Bar Sport / Re: Solder/Sodder on: August 08, 2014, 09:00:23 pm
I wonder if any shop [store] there claims to have 'sod out' of an item?
Here, we might be told [tod?]  they have sod all left, but that's not quite the same.  smiley-grin
88  Community / Bar Sport / Re: How do they weigh.... on: August 08, 2014, 08:44:52 pm
Yup, every time I see a kid's balloon floating away, and I think "some unborn physicist is cursing you!"

(Of course, once we've got fusion, we'll have more helium ash than we know what to do with)
We could bury it... smiley-mr-green smiley-lol smiley-lol smiley-lol smiley-lol
89  Using Arduino / General Electronics / Re: Gauging Interest: Printed Circuits on Paper on: August 08, 2014, 07:59:14 pm
Maybe I missed where the original poster gave the conductivity of the ink?
The folks with the idea on Kickstarter say 0.2 Ohms/square.
Square what, acres?   smiley-wink
Doesn't matter. The resistance of a square of material is the same whatever size it is. Width and length change at the same rate so, if you double its length, you also double the width. Increased length increases the resistance but increased width decreases it. In a square the changes cancel each other out.
90  Using Arduino / General Electronics / Re: Rotary relay? on: July 15, 2014, 10:44:08 pm
There used to be a device using a stepping motor coupled to a rotary switch. This was many years ago; I think it had around 10 to 12 positions. I used them for remotely switching  the tip and ring of telephone circuits. In this digital telecommunications age, there is probably no demand for switches like this anymore. You might find them in an electronics surplus store, if you're very lucky.

If it were me, I would go to a solid state solution.
I think you're referring to a motorised Yaxley switch. Yaxleys were great because you could add 'layers' to make multipole switches. The only problem was, with too many layers they became too stiff to turn.
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