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1  Topics / Robotics / Re: Inverse trig functions on: April 07, 2013, 09:31:27 am
These are about the cheapest servos you can get:

http://www.ebay.com/itm/Micro-9g-Mini-RC-Servo-for-Trex-450-Futaba-Hitec-HS-55-Align-GWS-JR-Walkera-Heli-/140922521530?pt=LH_DefaultDomain_0&hash=item20cfa307ba

Yep, straight from china.  Keep in mind that you get what you pay for.
2  Topics / Robotics / Re: Inverse trig functions on: April 05, 2013, 07:34:39 pm
The value of Pi isn't included with math.h.  You should just do something like:
Code:
#define PI 3.14.....
Then you can just use the "PI" definition where needed.

Arduino.h already defines PI
Even Better
3  Using Arduino / General Electronics / Re: Strange values from 2ch receiver on: April 05, 2013, 04:50:12 pm
This may be a good choice:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8338
I'm not very sure what kind of transmitter you are looking for.
4  Using Arduino / Motors, Mechanics, and Power / Re: PWM Motor noise issues on: April 05, 2013, 04:44:14 pm
Hmmm...This is tricky.  You might want to try to add a capacitor (about 100uf) across +5 and GND to filter out noise.  If that does nothing, I would suggest a more powerful supply.
5  Using Arduino / Project Guidance / Re: remote sensors - wich (wired) connection is better? on: April 05, 2013, 04:40:46 pm
What you could do is use some of these:
http://www.ebay.com/sch/i.html?_trksid=m570.l1313&_nkw=arduino+rf+kit&_sacat=0&_from=R40
Each censor would have one of these radios with something like an attiny to handle the rf protocol. There would be one arduino connected to your PI to receive all the signals.
6  Using Arduino / Motors, Mechanics, and Power / Re: PWM Motor noise issues on: April 05, 2013, 04:32:40 pm
How is your arduino connected to the power supply?  Is the supply being applied to 'vin' or '5v'
7  Using Arduino / General Electronics / Re: Strange values from 2ch receiver on: April 05, 2013, 04:29:59 pm
I have used modern AM 27mhz receivers and typically when the transmitter is off, the the receiver outputted little noise.  Cheap rc cars and planes ship with these am radios still. They are not uncommon.  Try seeing what the arduino reads if there is absolutely nothing else drawing power from the system.  Also, some code would help.
8  Using Arduino / Motors, Mechanics, and Power / Re: PWM Motor noise issues on: April 05, 2013, 04:23:40 pm
For future reference, if you were running the motors from the +5v line on the arudino, that was your problem.  The motors were drawing too much power causing the voltage in the atmega to cause it to reset.  Always run high current devices from other supplies.
9  Topics / Robotics / Re: help designing tiny solenoids on: April 05, 2013, 04:19:32 pm
They are both good ideas.  Solenoids are fast but not often powerful.  The actuators are stronger but may be slower.
10  Topics / Robotics / Re: Inverse trig functions on: April 05, 2013, 04:16:45 pm
The value of Pi isn't included with math.h.  You should just do something like:
Code:
#define PI 3.14.....
Then you can just use the "PI" definition where needed.
11  Using Arduino / LEDs and Multiplexing / Re: 4 buttons on one digital IO on: April 04, 2013, 10:22:08 pm
A shift register would only require 3 pins. Not to mention that you can use your extra analog pins as regular digital pins.

Example: digitalWrite(A0, HIGH);

Also, you can link more than one shift register together while only using the same three pins.
12  Using Arduino / General Electronics / Re: Strange values from 2ch receiver on: April 04, 2013, 10:02:46 pm
I have run into these problems time after time when running Arduino off external power.  What you should do is to add some capacitors across 5v and GND.  It's generally a good idea to do this with any power supply to eliminate noise.  If you are using the Arduino to regulate it's own voltage, put caps between vin -> GND, and +5 -> GND.

EDIT:
Also are you doing anything else with your Arduino?  What I mean is when your are reading the values is anything else happening or drawing power?
13  Using Arduino / Project Guidance / Re: Intercom link ? on: April 04, 2013, 05:41:50 pm
I have also never worked with the ethernet shield, but it would be a good option.  What you could try is to use a mp3 shield that would record messages.  Then, the ethernet shield could send the files to a server somewhere.  If you wanted to send a message back, you could write some easy web app to record and send a mp3 back to the Arduino to be played.
14  Topics / Robotics / Re: Inverse trig functions on: April 04, 2013, 05:21:56 pm
This may help http://arduino.cc/forum/index.php/topic,44229.0.html  
What happens if you just try something like:

Code:
float invsin = asin(num);
15  Topics / Robotics / Re: help designing tiny solenoids on: April 04, 2013, 08:00:06 am
If you have ever taken apart the disk drive from an older laptop, you will fond that little solenoids are used to pop out the disk tray.  They are somewhat similar to these:

www.sparkfun.com/products/11015 
http://www.adafruit.com/products/412

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