Hi all, I have created a new toy for my 2nd granddaughter. It is a wireless application using two Netduinos, XBee wireless transceivers and a handful of resistors, LEDs and transistors. One side is a button she presses and the other side receives a wireless signal and then spells out her name (Evalyn) using LEDs.
I used an Arduino screw shield on both sides and soldered an XBee to both. The XBees worked right out of the box and are a simple joy to use. All I soldered were the TX/RX leads and 3.5V power and GND on the XBees. The LED matrix was made of a wire like the kind you would find for plastic flowers to hold LEDs and were separated simply by heat shrink tubing. I could've purchased an LED display of course but I wanted the 'handmade' look. I did solder all the LED rows to each other but it goes pretty quick once you get the soldering iron hot and have the matrix set up.
The ground of the LEDs went down the columns and the power lead across the rows. The rows were 5V and the columns were terminated by an npn transistor controlled from the Netduino. I got by with a 100 ohm resistor for the 2.3V LEDs due to the effect of PWM when providing current to the LEDs. As such I needed 16 control leads (6 rows and 10 columns) which the Netduino, with the analog lines, nicely provided so I didn't have to buffer control signals via a shift register or the like. The button side simply polled for a change in state and provided power to the LED inside the big plastic button. I got the clear button (recipe) box and the display for the LED side from a container store. It was very simple and a lot of fun especially with the ease of interrupt enabled debugging and the great IDE in general available on the Netduino using C# and Visual Studio.
My only observation is that sometimes you 'get what you pay for' as in the case of the wireless part of the toy I first tried an inexpensive transceiver and found it interfered with other devices around the house like the garage door opener. It also picked up quite a bit of impulse noise across the frequency of interest from all sorts of stuff which resulted in false button pushes. The XBees were the answer although they did cost a bit more.
The source for the project is on my website at
Here is a link to the video
My first toy used the Arduino Nano. You can see it here:
I really enjoy building things using the Arduino/Netduino family of processors and find this foum indespensable
Randy Brown ( aka grandpa Randy)