I got a basic pen from penteractive.us and got everything setup in the classroom. When I first got it all setup and calibrated it worked awesome for about 5 minutes. Then when I would hold down the button to draw a line it would skip and I would just get dots across the screen. I went and put new batteries in the pen and then it worked right away again for about 5 minutes after which the same problem arrived. I tried turning everything off and resetting up and still had the same problem. Once the initial 5 minutes of use are up it doesn't matter what I do it continues to jump around unless I put new batteries in.

Am i doing something wrong? I would imagine the batteries should last more than 5 minutes.

Thanks for the help.

Buy a pen with a resistor.  I'm just saying. If you don't limit the current in the circuit with a resistor, then yes your battery will be drained more quickly.

To ZMcElroy:

Before conclusions are drawn about the functionality of an item that has been purchased by 1000s of people and used very successfully, there are perhaps other questions that need to be raised.

1) What is the software being used to create the whiteboard (Smoothboard, Pentabulous, or WIWB for Mac) and on what platform (Windows XP, Vista...or Mac)?
2) How is the wiimote being positioned relative to the surface it is being focused upon?

Once we establish some basics on how you are using the pen, then we can progress further into why you are experiencing difficulties.

To shakespeare1212:

It is my understanding that a resistor only drops the amount of voltage being produced pushed through a component. Though certainly this means that an LED will last longer and not burn out as soon with a resistor in series, it does not guarantee longer battery life as the amount of current flowing out of the battery is constant when the circuit closed. The amount of voltage not used is given off as heat at the resistor if my rudimentary understanding of electronics is correct.

Hi Ben,

As a degree holder in Electrical and Electronic Engineering, I would like to clarify this issue regarding the existence of a resistor. This can be illustrated in a simply lay man scenario, if you connect the ends of a battery with a wire (low resistance), you will find that the battery will lose its power quickly. Therefore, the current flowing out from a battery is certainly not constant but depends on the circuit.

In high school physics, the common expression V=IR (Voltage = Current * Resistance), Ohm's law can be used. The larger the resistance, the smaller the current will pass through the resistor. Therefore, in the electrical circuit, the resistor is also called a current limiting resistor to control the current going through.

For a ordinary bulb, it acts as a resistor and thus the current going through the bulb follows the Ohm's law. However, the IR LED does not act like a resistor but is actually a diode. When the LED is working in the forward bias mode, there is a voltage drop called the forward voltage.

To calculate the optimum resistance for a specific IR LED, the following formula can be used
Resistance = (Supply Voltage - Voltage Drop (Forward Voltage)) / LED current rating according to specifications

Without a resistor, the current flowing through the diode will be quite large. As there is no external resistor present, we have to take into account the battery's internal resistance to be fed in the formula below. Usually with the presence of a resistor, the internal resistance is negligible.

Current = (Supply Voltage - Voltage Drop (Forward Voltage)) / Limiting Resistance

It can be seen that having a low resistance in the LED circuit will certainly have a large current flow through the LED. This will certainly cause a loss of power compared to using a resistor.

Hopefully this will benefit students who may be reading this forum.

Regards,
Boon Jin

Link:
http://www.vishay.com/docs/81011/tsal6400.pdf