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1  Forum 2005-2010 (read only) / Interfacing / Re: Pin 13 problem on NG on: August 16, 2007, 02:14:30 pm
Thanks, It is good to know that my analysis of the problem is correct, but I wonder why you connected the d13 header to pin 19 via a resistor instead of a jumper.
PS Any tips on searching for this are welcome. I searched for pin 13 did not find the very helpful thread that -j references.
2  Forum 2005-2010 (read only) / Interfacing / Pin 13 problem on NG on: August 16, 2007, 09:44:45 am
  I can not seem to be able to use pin 13 for any use other than the on board LED.  I read that tne newer boards have the LED disconnected.  Are there any tricks that I need to know to hook this pin to my motor controller (other pins work fine but I need 1 more line.)
According to the NG v4.0 schematic (how do I know if this is the right one for my board?) there are 2 470 Ohm resistors from the AVR to the header wth the LED between.
Should I wire pin 19 to the header?
What about ISCP? wll I need to disconnect my motor control to use it?
3  Forum 2005-2010 (read only) / Interfacing / Re: Piezo Speaker on: July 03, 2007, 07:06:41 am
Thanks for the info.  I have a 96 Ohm resistor but I did not think about the inductance and thus did not add a diode.
PS It seems wise that the tutorial should be updated. I am willing to help with this.
4  Forum 2005-2010 (read only) / Interfacing / Piezo Speaker on: July 02, 2007, 11:11:15 pm
I have hooked up a piezo speaker from an old cell phone and loaded the code from
 I have my PWM outputs taken by motors so I put the speaker on digital pin 3 and modified the code accordingly.  It works the same.
SO my questions:
  Why do they say I need to use the PWM outputs? (9,10 or 11)
  Will I damage the chip?
  Is there a max frequency for the other (not PWM) outputs?  I could not find that info in the data sheet
5  Forum 2005-2010 (read only) / Interfacing / Re: water level sensor on: April 23, 2007, 10:56:29 pm
There are so many options!
If you need great reliability go with a comercial sensor (and there is a bewildering array of them) Check out
If you are making your own consider these ideas.
-A Sharp IR distance sensor looking down to the liquid
-same Idea with a sonar sensor
-A float with a magnet and a hall effect sensor (sensors can be found with open collector and ttl outputs)
-Not green but you could find an old thermostat with a Mercury switch and put it on a tilting float
-Lots of circuts that use the conductivity and/or capacitance of the water are available on the internet.
-if you are actually using a 2 liter bottle you could arrange opto sensors to look through the bottle and note the change in transparency.
Figure out your needs and take a pick
6  Forum 2005-2010 (read only) / Interfacing / Re: Smoothing Ultrasonic Rangefinder Data on: May 06, 2007, 10:52:53 pm
Yet Another Method

Approximate Moving average
where n is the sample number. thus MovAve(n-1) is the previous MovAve
Pick any interger for NumPts - Bigger is smother.
MovAve =  MovAve(n-1) + Data/NumPts - MovAve(n-1)/NumPts
MovAve =  MovAve(n-1)  - MovAve(n-1)/NumPts + Data/NumPts
MovAve =  MovAve(n-1) * (NumPts - 1)/NumPts  + Data/NumPts

7  Forum 2005-2010 (read only) / Interfacing / Re: motor and mechanics on: April 24, 2007, 10:35:52 pm
check out
The tech library link on the left has more info that most need or want.
8  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: 3.5 floppy motor wiring? on: February 26, 2007, 11:59:41 pm
You can drive a floppy step motor directly from the arduino. BUT you need to keep the floppy controller board.  The control has a 5V logic interface that controls the steps, the direction and the home position sensor.  I had to read all 3 of these before I understood it.

5.25 and 3.5 drives have the same wiring just a different connector style
 You can also hack the disk motor and the sensors
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