Posted by bill.french on 22 November 2010 - 03:43 AM in Netduino 2 (and Netduino 1)

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Posted by bill.french on 14 November 2010 - 12:41 PM in General Discussion

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Posted by bill.french on 09 November 2010 - 07:31 PM in General Discussion

ok i think I got this right -- i believe the right most pin is the - and the center pin is the +:



Is that about what you're doing, with the multimeter/analog input hooked up after the resistor?

Posted by bill.french on 09 November 2010 - 07:12 PM in Visual Studio

Posted by bill.french on 09 November 2010 - 06:32 PM in General Discussion

Posted by bill.french on 09 November 2010 - 06:31 PM in General Discussion

Posted by bill.french on 09 November 2010 - 06:29 PM in Visual Studio

Here's what I would do. I am not an expert on anything so... you're on your own.

Looking at the below diagram, look at the circuit on the right, since a motor is an inductive load. I would skip RC, because I am hardcore. RB i would start with a 1k Ohm. I would use just about any NPN resistor, RadioShack should definitely have them, I think they sell a 10 count variety pack. For such a small motor almost any diode would do, something like this should be fine: http://www.radioshac...oductId=2036269

Is it safe to assume you understand the symbols in the diagram for the diode, transistor, etc?

Posted by bill.french on 09 November 2010 - 06:15 PM in General Discussion

I'm sorry, I don't know. According to this picture:



If your room is 72 degrees F, which is 295 degrees K, you should have a reading of about 2.95V, I think.

When you're measuring with the multimeter, is the netduino involved in the circuit at all? I would start with the netduino out of the picture entirely a focus on getting the right readings on a multimeter, then focus on getting them well below 3.3V to be safe for the analog inputs.

Posted by bill.french on 09 November 2010 - 06:08 PM in General Discussion

Posted by bill.french on 09 November 2010 - 06:04 PM in General Discussion

Posted by bill.french on 09 November 2010 - 01:48 AM in Visual Studio

Posted by bill.french on 09 November 2010 - 01:41 AM in General Discussion

This post covers:

• a very basic circuit using a potentiometer
• a program for reading an analog input port

First, the circuit. You'll want to read about voltage dividers to really understand what is happening. The potentiometer acts as one of the resistors in the voltage divider -- and since a potentiometer's resistance changes by turning it, it provides a good source for the analog input. If you are comfortable with Ohms Law (V=IR) the wikipedia article on voltage dividers is pretty approachable in my opinion. Something important in the circuit is the link from 3.3v to the aref pin. Aref is "analog reference" and sets the ceiling of the analog input. The max is 3.3v. I believe the revision B netduino boards have an internal tie in so that using aref is optional.



... and what it might look like on a breadboard:


... and the program:

using System.Text;
using Microsoft.SPOT;
using System.Threading;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;


namespace NDP_SocketSender1
{
    public class Program
    {
        public static void Main()
        {
       
            AnalogInput a5 = new AnalogInput(Pins.GPIO_PIN_A5);

            while (true)
            {
                string s = a5.Read().ToString();
                Debug.Print(s);
                Thread.Sleep(100);
            }
        }
    }
}

Basically, the program opens up an analog input port (a5 in this case), reads the value into a string, and prints the string to the output window in visual studio every 100ms. As you adjust the potentiometer, the values displayed in debug should change, varying from about 0 to about 1023, which are the bounds of the 10-bit ADC (analog-digital coverter) built in to the netduino.

Since I have a Netduino Plus, I have also set it up send the readings over the network and graph them in a Windows Forms Application, so I could see the results visually as I turned the potentiometer to different positions. It's important to realize that digital inputs read either 1 or 0; analog inputs have a range, and the graph from my netduino plus illustrates this:



If you don't have a netduino plus, you can cut and paste the data from the output window in Visual Studio into Excel or a Google spreadsheet and graph from there.

If this is interesting to you, I would encourage you to search the forums for "analog", "analoginput", and "setrange" for lots more useful information.

Posted by bill.french on 09 November 2010 - 12:52 AM in Visual Studio