Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: VegaObscura on June 28, 2009, 07:56:32 AM
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I've spent nearly a week trying to figure out how to use them. I'm not talking about anything fancy, I just want to use one as a switch. In this learning experiment I want to have a battery going to a led, with a transistor controlling whether its on or off. I intend to have another power source going to a button which then goes to the transistor to turn the transistor on or off. Here's the part that I can't understand. Transistors have 3 pins. That just fries my brain. If transistors were a 4 pin component, it would be easy to comprehend. + and - of the circuit to be turned on and off by the transistor would connect to the 2 pins on one side, while the circuit turning the transistor itself on and off would connect to the other 2 pins. But that's obviously not how it works, since they have 3 pins. Everywhere I try to read about them loves to talk about the fact that they can be used as switches or can be used to amplify current, but I can't find anywhere telling about how to actually use them in a circuit.
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http://www.allaboutcircuits.com/vol_3/chpt_4/2.html (http://www.allaboutcircuits.com/vol_3/chpt_4/2.html)
The circuit turning the transistor on/off does not need 2 pins since the ground is common with the circuit to be turned off/on.
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Okay, I think I understand. So let's say the side with the battery and led is circuit 1. The battery and button is circuit 2. So I should connect + from circuit 1 to one pin, + from circuit 2 to another pin, and ground from both circuits to the third pin? That's a little hard for me to comprehend, but I think I got it.