I recently purchased a Velleman Sound to Light soldering kit. I thought it would be easy to understand even as a beginner electronic hobbyist but I am having some issues.
Please take a moment to check out the kit schematics:
Ref: datasheet of BC547
I have limited knowledge about how all these works but there are some parts of the circuit that are particularly troublesome for me to understand. Here are a couple of questions:
What is the purpose of the C4 capacitor? Is this what it’s known as the bulk or smoothing capacitor?
Why does’t the T3 transistor have a resistor on the emitter leg? Don’t you need that resistor (for negative feedback) to be able to stabilize the transistor such as preventing thermal overrun, minimize beta variations effects between transistors etc?
What is the purpose of resistor R8? It looks like its on a weird place being in series between the power supply positive lead and and half of the circuit, what is up with that?
What is the point of having R12 and R5 as two separate resistors? Can’t those two resistor be replace with a single resistor and achieve the same affect?
Why aren’t the biasing resistors (voltage dividers) on T1 and T2 not identical? Its the exact same transistor so why is the voltage divider biasing different (specifically on R2 and R10)?