Experimenting with photodiodes and learning basics
In the last few days I've learnt a lot of new things. One of the most important - how to handle high-current electric circuits. The power that comes out of Arduino pins is enough to power some leds or write some text on a LCD display, but it's not enough to power a DC motor or other devices. Arduino pins output up to 40mA of voltage, while the DC motors I have require around 350mA. While finding out the ways of passing more current to my DC motors I found a great site explaining these basic things in a very understandable manner:
Actually I would recommend reading all of the pages listed on the left in this site. It really helped me clarify a lot of things as a beginner in electronics.
As about DC motors, I chose to buy the most simple DC motors available - I thought buying servo or stepper motors for the experiments is too expensive, but I'll get to that. If you are working with servo or stepper motors, there are special Arduino libraries for that.
Yesterday I also got my order with photodiodes that I'll use for my line follower robot project. After putting them into my solderless breadboard I used a multimeter to measure their values. Ininitially I thought the difference in the readings will be much more diversed if I cover or uncover the diodes. After connecting them to arduino analog inputs and reading their values arduino told me their values when being covered and uncovered differ only by some 20 units (one unit is equal to 0.0048volts). I did the tests by facing the diodes up to the ceiling, next I need to check how do they react to reflected light from the ground and from the track. As about line following robots in general - if you're looking for a ready-made line following sensor, you can get one, but my aim is to build everything by myself. And .. it costs less to build one by yourself.
I guess I need to start planning the actual design of the robot and do some battle-field tests with the diodes facing the track. Stay tuned!