3.6 - Computer Power

Safety Warnings

Always disconnect from the power source when working on a device.

Some devices store a charge in capacitors.

• Know how to discharge these before touching. 

Never connect your body to any part of an electrical system. 

• Do not connect yourself to the ground wire of an electrical system. 

Respect electricity. It does not respect you. 

Computer Power vs Wall Power

Computers use DC Voltage.

Most power sources provide AC Voltage.

Convert 120 Volt AC (American) or 240 Volt AC (European)

• To 2.2 V DC, 5 V DC, and 12 V DC.

You’ll know when this isn’t working. 

Amps

The rate of electron flow past a point in one second.

• The diameter of the hose.

Volts

Electrical “pressure” pushing the electrons. 

• How open the faucet is.

Watts

Measurement of real power use.

• Volts x Amps = Watts

• 120V x 0.5 A = 60W

Current

Alternating Current (AC)

• Direction of current constantly reverses. 

• Distributes electricity efficiently over long distances. 

• Frequency of this cycle is important. 

• US/Canada - 110 to 120 volts of AC (VAC), 60 hertz (Hz)

• Europe - 220-240 VAC, 50 Hz

Direct Current

• Current moves in one direction with constant voltage. 

Dual-Voltage Input Options

Voltage varies by country. 

• US/Canada - 120 volts of AC (VAC), 60 hz (Hz)

• Europe - 230 VAC, 50 Hz

Manually switch between 120 V and 230 V

• Get your meter!

• Or use an auto voltage power supply.

Don’t plug a 120 V power supply into a 230 V power source!