ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
twh 10
Admin 4
Recent Posts
Windows 10, who's upgraded?
by geoff in UK. 05/29/17 01:05 PM
How do you find a good employee?
by ElectricianBud. 05/27/17 10:58 AM
Recall notice: Bosch Solar panels
by ElectricianBud. 05/27/17 10:53 AM
Correct rotation, wrong sequence
by Potseal. 05/27/17 12:15 AM
Dryer, Range grounding from "Main" panel
by sparkync. 05/25/17 05:49 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
236,989 Are you busy
172,005 Re: Forum
164,881 Need opinion
Who's Online Now
0 registered members (), 63 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#3660 - 08/25/01 10:37 AM Computer usage  
Mike Shn  Offline
Member
Joined: Jun 2001
Posts: 25
New York
Hello

Does someone know the consumption of voltage for computer and what kind of current computer use (AC or DC)? Also what usage have radio and telephone?
Thanks a lot


Work Gear for Electricians and the Trades

#3661 - 08/25/01 04:10 PM Re: Computer usage  
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
Voltage is not consumed, so I presume you are asking how much power is being used. Look carefully at each device, somewhere there will be electrical information that includes either watts or volt-amps (VA) which is roughly (there is no exact conversion) comparable to watts.

Voltage input into any computer I ever met was AC which is converted to DC.

Tom


Few things are harder to put up with than the annoyance of a good example.

#3662 - 08/25/01 11:49 PM Re: Computer usage  
mickky  Offline
Member
Joined: Jul 2001
Posts: 43
toronto
Quote
Originally posted by Mike Shn:
Hello

Does someone know the consumption of voltage for computer and what kind of current computer use (AC or DC)? Also what usage have radio and telephone?
Thanks a lot


All computers contain a transformer/power supply which converts AC to DC-many new computers, with large display terminals and speakers connected can consume up to 400w-large SCSI hard disks run at up to 10,000 rpm.
Not sure about phones, but I do know that they actually run on batteries in normal operation, sort of a UPS, as it were. Radios, stereos can be determined by looking at the nameplate on the unit. Their consumption varies according to the speaker rating/volume. Some high end systems with monster speakers attached will actually deliver straight AC to them. They contain no transformer, and generate considerable heat. I believe they are known as Class B, with regular stereos known as Class A/B switching Amplifiers.


#3663 - 08/26/01 05:09 AM Re: Computer usage  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
Originally posted by mickky:

Not sure about phones, but I do know that they actually run on batteries in normal operation, sort of a UPS, as it were.


Exchange battery voltage is 48 to 50V, positive pole grounded. A standard tel. line is fed through a relatively high resistance, so current is limited to the tens of milliamps range and off-hook voltage across the phone is typically 5 to 12V, depending to a large degree on line length. Power consumed by the phone itself is therefore minimal. Ringing supply is AC at up to 100V, but again power consumption is very small.

Quote

I believe they are known as Class B, with regular stereos known as Class A/B switching Amplifiers.


A push-pull audio output stage can operate in class A, B, or A/B.

Class A means that both transistors (or tubes) are conducting all the time. As one conducts more heavily the other conducts less, and vice versa.

With class B, the transistors are biased to cut-off point, so with no signal there is no (or very little) current. One transistor then conducts for positive parts of the signal, the other for negative portions.

Class A generally offers better fidelity, but because of the quiescent current it is much less efficient than class B.

Class A/B is a compromise between the two. With a low-level signal, both transistors conduct and the amplifier works in class A. At higher levels, one transistor cuts off during positive peaks, the other during negative, effectively changing the mode to class B.
While class A/B isn't as efficient as class B, it avoids crossover distortion which can sometimes be a problem with class B.


#3664 - 08/26/01 05:35 AM Re: Computer usage  
mickky  Offline
Member
Joined: Jul 2001
Posts: 43
toronto
Quote
Originally posted by pauluk:
A push-pull audio output stage can operate in class A, B, or A/B.

Class A means that both transistors (or tubes) are conducting all the time. As one conducts more heavily the other conducts less, and vice versa.

With class B, the transistors are biased to cut-off point, so with no signal there is no (or very little) current. One transistor then conducts for positive parts of the signal, the other for negative portions.

Class A generally offers better fidelity, but because of the quiescent current it is much less efficient than class B.

Class A/B is a compromise between the two. With a low-level signal, both transistors conduct and the amplifier works in class A. At higher levels, one transistor cuts off during positive peaks, the other during negative, effectively changing the mode to class B.
While class A/B isn't as efficient as class B, it avoids crossover distortion which can sometimes be a problem with class B.


Thanks for the much more informed responseto the original post, Paul. Am I being misleading about one class of amp being transformerless, or is it a different animal altogether?


#3665 - 08/26/01 07:08 PM Re: Computer usage  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
Originally posted by mickky:
Thanks for the much more informed responseto the original post, Paul. Am I being misleading about one class of amp being transformerless, or is it a different animal altogether?

Glad to be of service.....

There is no specific link which requires any particular class of operation to use or not use a transformer to couple to the speaker. It's possible to build an amplifier in any of the three classes A,B, or A/B either with or without such a transformer.

With old tube amps a transformer was almost always used, as it's the easiest way to couple power from the high-impedance tubes to the low-impedance speaker.

Many early transistor amps also used a transformer. The higher-quality units ran class A or A/B. Class B was especially common in battery-powered portables, due to the higher efficiency & thus lower battery drain.

Because transistors are lower-impedance devices than tubes, direct coupling is also easily achieved, and is the norm in modern amplifiers. The absence of the transformer is said to remove a possible source of distortion, but another advantage is that transformers for high powers and bulky and expensive.

It's still possible for a transformer-less output stage to run as class A, B, or A/B, however.

There is also a class C, but this is not suitable for audio applications.


#3666 - 01/07/04 10:46 PM Re: Computer usage  
cpalm1  Offline
Member
Joined: Jan 2004
Posts: 66
now they've got class D amps for subwoofers in car audio systems. I hear they are very efficient and generate less heat, so cooling is not as big of a factor. they are also cheaper than class AB amps. They can only be used for subwoofers though



Member Spotlight
The_Lightman
The_Lightman
Orlando, Fl, USA
Posts: 49
Joined: August 2001
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.014s Queries: 14 (0.003s) Memory: 0.7877 MB (Peak: 0.9387 MB) Zlib enabled. Server Time: 2017-05-29 22:48:31 UTC