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1  Using Arduino / Project Guidance / Re: Feasibility of Arduino based ball catching system on mobile platform? on: September 02, 2014, 04:02:33 pm
With the system you proposed, if you just held the ball in the air and dropped it straight down, the robot would have enough time to see the ball and drive to center and catch it.  If you want to toss the ball it gets harder, as you need to make sure the robot is fast enough to keep up with the ball, as it won't be able to predict where the ball is going to go, only follow it.  That said, it is a simple way to start and in some cases it may work.  Give it some thought, sketch it out, and if you still like the idea try it.
2  Using Arduino / Project Guidance / Re: Feasibility of Arduino based ball catching system on mobile platform? on: September 01, 2014, 11:07:16 am
Cool video.  My attempts at answering your questions follow.

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Can an arduino process such fast trajectory?

Maybe, but you would need to take some significant shortcuts in the math to attempt to make the problem simpler.  The team in the video was running their trajectory calculation on a separate server, so scaling that down to an Arduino is likely very hard if not impossible.  The more reasonable solution is to do the vision tracking and trajectory calculation off the Arduino and feed it simple movement commands.

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Should I do my image processing part on a on board computer and then send the information to arduino serially  for                  further processing ?

This sounds like a better idea, but even a single board computer may have trouble doing all the calculations you need fast enough.  I might start out with a good PC and then see if you can reduce it down to an SBC.  My college senior design team did some fairly basic computer vision and we found that we barely had enough CPU power on a serious engineering workstation.

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Does camera needs to be off board the platform or can be integrated on platform?

I don't think it will mater greatly where you mount the camera. 

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What type of camera I would need?
 

Probably doesn't matter greatly either.  I would start out with a USB webcam on a PC.  Standard Arduinos aren't meant to interface directly with cameras.  There are some hacks, but none with the performance you would need.

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Also would one camera be sufficient for the task?

Based on your video, I would say yes.  But realize that these are likely grad students working on a thesis project, so it may be well beyond the typical hobbyist.  More cameras may make the calculations easier, but then you also have more video streams to deal with as well, so the overall system may be just as hard to produce.
3  Using Arduino / Project Guidance / Re: Robot arm for PCB etching on: September 01, 2014, 10:50:43 am
I have seen these robot arms in person before.  They seem robust enough, but they are certainly in the toy category.  Note that they are quite small and are by no means fast, but that may be fine for your application.   You might be able to add you own motor controllers and potentiometers/encoders to make it fully autonomous, but at that point you be equal in work and $ to somthing more purpose built. 
4  Using Arduino / Project Guidance / Re: good method for remote control dc motor? on: August 30, 2014, 09:00:56 am
You are correct, even if you just wanted to send the value from the pot, it makes no sense to turn it into a string, transmit the string, and parse it back into an integer on the other end.  Instead you might consider dividing the value by 4 so it fits into a single byte and then transmitting that byte.  Now in the space of one character you have sent the whole number and there is no need to parse the value on the other side. 

Check out the difference between the Serial.print and Serial.write functions to see this difference over the debugging terminal.
5  Using Arduino / General Electronics / Re: Switch, Relay and Backup line. on: August 30, 2014, 08:48:56 am
Quick question:  What sort of light are we talking about?  The reason for asking is that the solution for a small LED light running on 5VDC is very different than the solution for a standard wall voltage lamp running on 110-220VAC.
6  Using Arduino / General Electronics / Re: Help with thermistor power filtering circuit on: August 30, 2014, 08:38:30 am
Most of your assumptions are fairly good.  The point of everything on the left side of this schematic is just to make sure you have a very clean 5V feeding the right half of the schematic.  RP is 1-10 Ohms not KOhms. 

I am no expert on inductors, but given that this one is meant to be a filter I would think a simple RF chock is what is being called. out.  The electrolytic caps are again just being used as filters so the exact value is less critical than the presence.  The exact values will affect what frequencies get filtered more than others, but unless you know your noise sources you can't really say which would be best.

The only truly necessary components on this schematic are the thermistor and the fixed resistor used to form a voltage divider that you measure with the ADC.  Everything else is just helping to remove noise from the signal.  You could opt to just hook up the minimum first and if the result is too noisy then add in the rest.
7  Using Arduino / Project Guidance / Re: Laserpointer light detecting POV idea on: August 10, 2014, 04:04:15 pm
I haven't done anything like this, but from an electrical and code perspective I don't see any reasons why this wouldn't work.  Sounds like a cool project.
8  Using Arduino / Project Guidance / Re: Coal Friction Tester - New to Electronics on: August 10, 2014, 03:50:52 pm
If you want very smooth motion you will want to make sure you have a soft connection between the pivot mechanism and the stepper motor.  I have made these before using a short length of rubber "surgical" tubing to connect the two shafts.  You loose some accuracy in the soft connection, but it will smooth out the jerky steps.  I am not sure I would use rubber tubing for something you wanted to be reliable in industry, but I am sure there are other ways of doing this that would be reliable enough.  

So long as you use micro-stepping and have a high gear ratio between the stepper and the pivot mechanism I wouldn't be too worried as the vibration will be geared down.  If you wanted to design for completely smooth motion from the ground up, I would use a plain old DC gearmotor to rotate the platform.  You can then add a potentiometer or other sensor to measure the rotation of the platform and write you own code to move the motor smoothly to the desired position.
9  Using Arduino / General Electronics / Re: Powering Arduino Uno using AA batteries on: July 30, 2014, 05:35:05 pm
If you must have 5V coming into the Arduino you might try using  a switching mode regulator much like this one.

http://www.pololu.com/product/2121

Its tiny, cheap, and it can accept a huge range of inputs and turn them into 5V.  Pololu has other options if you need more current or a different input range and they even have built part this into battery holders.  Any of these options give you exactly the voltage you need AND good battery life.
10  Using Arduino / Project Guidance / Re: Coal Friction Tester - New to Electronics on: July 30, 2014, 05:28:48 pm
Give the stepper motor a try and you might find it has enough vibration by itself.  Stepper motors move in jerky steps that could in a way emulate a vibrating belt.  You could also add some jitter to the step pattern (2 forward, 1 back, 2 forward...), but this might give you some issues.

 The simplest way to add vibration would be to use a DC vibrator motor to shake the test table independent of the main tilting motor.  Vibrator motors are motors with a rotating mass that is off center so as to cause the motor to vibrate.  A simple DC motor controller could drive one at different speeds, and altering the mass could change the intensity of the vibration.

As for coding, just break out a piece at a time.  Step 1 in my book would be to make the motor turn constantly in one direction.  When you can do and understand that try different speeds or both directions and slowly add features until you are there.  Breaking out self-sufficient code into functions can help a lot with Arduino.  Classes and anything more complicated usually are not worth the overhead for a small one-off project like yours, but a lot of that comes down to programmer preference. 
11  Using Arduino / Project Guidance / Re: Building of flight controller on: June 25, 2014, 03:57:40 pm
I have a lot of friends who have used the MultiWii and MultiWii Pro flight controller boards.  They are Arduino based and are about as cheap as flight controllers come.  There are definitely much better flight controllers out there with much better sensors, but they are much more expensive.  Even the APM (ArduPilot Mega) is quite expensive for an Arduino based board.

I have looked at the MultiWii code and it is gigantic (For Arduino Code).  I think it had upwards of 20 different source code files many of which were thousands of lines long.  Writing it yourself would be exceedingly hard for all but the most experienced navigation and control theory programmers.

Having worked on a quad myself, I would plan to spend at least a few months of hard work on simply assembling and tweaking the quad-copter before you will have it flying well.  This would include about 3 crashes that necessitate replacing motors, and frame components and dozens of broken blades.  In all, you should be prepared to spend at least a few hundred dollars on this endeavor. 

In all, it is certainly doable (and fun), but you should know what your in for.
12  Using Arduino / Project Guidance / Re: Switching USB on and off on: June 12, 2014, 09:45:01 pm
What would happen if you simply cut the 5V line?  It would certainly never draw power from USB, but the data lines would still be there. 

The question I can't answer myself is if the Arduino or computer would ignore the data in the absence of the 5V line.
13  Using Arduino / Project Guidance / Re: Anyone ever try this? on: June 12, 2014, 09:40:43 pm
I'm surprised no one has mentioned the product Sparkfun stocks that cable for.  It seems quite applicable...
https://www.sparkfun.com/products/9555
14  Using Arduino / Project Guidance / Re: i need help for my graduation project on: June 12, 2014, 09:36:08 pm
Wow...

I just completed my own BSE electrical engineering senior design project, and I will admit that I did ask for some help here, but there is a BIG difference between what I asked and what the OP did.

This community (and your professor) is typically happy to answer questions like:
1.  I tried X, Y, and Z but I still can't get my code to upload, any ideas?
2.  Am I biasing this transistor correctly?
3.  Where might I find a source for X component?
4. Is this datasheet actually correct?

But if you expect us to do all of your project for you, you deserve to fail.  I spent well over 400 hours on my project.  If I did have the time, money, and ambition to do your entire project, write a good report, and complete the other requirements I certainly wouldn't turn all my work over to you so you could take all the credit! 

As a side note, I do have to disagree with Jack.  I have seen a few electrical projects at my College that seemed feasible to start with, but as the team developed their solution they found that due to the limits of their budget, time, or technology their project would not be feasible.  They actually did quite well as they were still able to put together something they could show worked to a degree and in their report they gave a detailed workup of why what they tried to do actually wasn't possible. 

In short: If you have a question ask your professor.  If they don't know the answer, go ahead and ask here, but if they tell you to find out yourself, get to work.
15  Using Arduino / Project Guidance / Re: ARduino for Stadiums ? on: June 12, 2014, 09:02:22 pm
I love Arduino as much as most of us here, but I agree with Jack.  If it were me I would find a switch that could switch the main voltages for the light and siren.  A double pole switch would keep both of these separate and connect both when the switch was triggered.  Multiple switches could be easily wired in parallel and the system would use no power when off at all!

The only downside I see with this way is that if the switch was re-closed the alarm and lights would turn off.  To prevent this you could use a switch to turn on a relay wired with some hysteresis such that once the switch is thrown the circuit will turn on and the relay  would stay on by itself until power was disconnected from the system.  If you want I (and probably other here as well) can post a schematic of this setup.  Even with the relay and hysteresis it would still use no power in standby.
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