Sunday, 13 July 2014

Build Your First Robot - Transistors (Little Deeper)

I was actually going to write a post featuring the applications of transistors. I even titled the post "Build Your First Robot - Transistors and their Applications", but then I thought , I must share a little bit more unorganized information about transistors. So, here it is!

As I have mentioned in my very first post, robotics is an interplay of mechanics, electronics and computer science. As we living organisms have sense organs to sense our environment, robots have sensors. Often this sensors are designed to work with a small power supply. Due to this, the output of these sensors are not strong enough to directly control the robot. Sensors' outputs often require amplification, and in theory we can use a common music amplifier with some modification for this purpose but as amplifiers draw a lot of current, in robotics transistors are used. Transistors are used as brains in many homemade robots and even the robots that have computers as their brains indirectly rely on transistors.

If you search the World Wide Web, you would find most of the circuits involving transistors based on an
n-p-n. This is because, back in the old times, n-p-n transistors were cheap and there were lots of them compared to p-n-p hence people got accustomed to design circuits with n-p-n transistors.

As I had mentioned in my previous post, in an n-p-n transistor the collector has to be more positive than the emitter and even a small amount of current can "switch on" the transistor and the current will flow from the collector to the emitter. Transistors are not connected directly to the power supply since a large amount of current can destroy them. Here is where resistors come in use. Resistors can be used to limit the flow of current to the required level. Now you might wonder how can you find the maximum current that a particular transistor may withstand without damage? It is easy! Just Google the name of the transistor and the search results will be flooded with lots of "datasheets". Choose one depending upon the manufacturer and you will have all the information that you will require while using the transistor.