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Electrical engineering

Course: Electrical engineering>Unit 9

Lesson 3: DVD player

What is inside a DVD player? (2 of 5)

In this video we explore the power supply inside a DVD player. Created by Karl Wendt.

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• At how does a radio uses electricity and how much ?
• it uses 5watt-hours, or after 200 days of such use
(1 vote)
• When he says noise, does he mean interference?
• Yes, the noise is any interference on the electronics.
• In what ways can the board fail?
• Is a diode like a light
• Hello Scout,

It depends on the type of diode. There is a class of diodes know as "Light Emitting Diodes" that do light up. You can purchase LEDs in all colors of the rainbow.

Other diodes are used to ensure that current only flows in one direction. These are available from nearly microscopic to devices that are bigger than your fist.

Regards,

APD
• Why does at he says the power only flows in one direction?
• He said that b/c he was talking about DC ,or Direct Current.
• Carl explains that some of the components help filter out "noise". But what is this noise and how can it damage the appliance?
(1 vote)
• AC which we normally get at our homes is generally a sine wave (not necessarily ac always be sine wave but sine wave is what we get at our homes). Since it's a sine wave it's value is always changing. But electronic devices, especially IC's require DC supply. That's why converter is used. When the AC is converted to DC, i.e. sine wave gets converted to straight line, the conversion is not always perfect. There are some ripples left in the signal and yes you can imagine this ripples as small wavy type ripples in water. However, our requirement is almost perfectly smooth DC (i.e. it does not contain any ripples - noise). So that's why filters are used.

Noise: Unwanted signals, in our case ripples present in DC

Effects of noise: Integrated Circuits (IC) are digital components and works on only two levels, generally 0 Volt (Logic 0) and 5 Volt (Logic 1). However, if ripples are present then there are chances of change in Logic and this unexpected behavior may damage the chip and ultimately the device.

Filters: Remove out the noise. The basic filters are inductors and capacitors.

Inductors have to capability to oppose change in current. Ripples are change in current since they are not constant valued therefore inductor opposes them and ripples are filtered out.

Capacitors have the capability to pass alternating current and block direct current. This is because the opposition that capacitor offers is inversely proportional to the frequency of supply. DC have 0 Hz frequency and AC has some HZ frequency. So capacitor opposes DC and pass AC. So the trick here is, capacitor is connected in such a way that it provides the path for the ripple to flow to ground and blocks DC and therefore DC flows to the circuit and ripples flow to the ground. Thus ripple is filtered out.
• why are there so many resisters?
• How does a transformer work exactly?