Huh? What do you mean that dead VGA monitor just saved you money? That is what I did not have to go to the electronics store to purchase an overpriced VGA cable just to be cut apart. Why would I want to do that? Most personal computers now have what is know as the i2c (pronounced eye-squared-see) bus coming from the video port. Even the better touchpads and tablets have this port. This means you can connect all kinds of sensing devices to your computing equipment.
Let's dig a little deeper. The most traditional sensors used are what is known as temperature sensors. They are electronic thermometers. So you could connect one or many of these sensors to the i2c bus off the computer's video port. Even some hdmi cables support this. Of course, you would need a special interface for your touchpad or tablet. But it is there.
What can we do with the temperature sensors. The sensors can be placed in computer server rooms, around entertainment equipment (especially projectors), and other sensitive places to monitor the temperature. The premise is that you do not want overheated equipment or even have the possibility of a fire hazard. The temperature sensors will send data back to the host computer and then software on the host computer can take action accordingly. Home automation software usually comes into play here. From that point of view that cable could save you thousands of dollars!!! (not just twenty dollars).
There are many many articles on how to implement the i2c bus, so I will not dwell on it here, Your favorite search engine can allow you to access the articles by searching on i2c. Often overlooked is what can we do with our computers besides just running our favorite computer programs. So, what about that VGA cable? Had a dead computer monitor in the garage. I needed a cable to build an i2c interface. Which means you need a cable that can be torn apart. Cut off the cable from the back of the monitor and then made the cable. Another reuse for dead equipment! Going green....
Building of the basic cable can be found at :
You can also use other ports on a computer for controlling other equipment and collecting data.