How do appliances handle varying voltage requirements?

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Discussion Overview

The discussion revolves around how household appliances manage varying voltage requirements, particularly in the context of devices designed for lower voltages than the standard 110-120 volts supplied by US outlets. Participants explore the mechanisms, such as transformers and pulse width modulation, that allow these devices to operate safely and effectively.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that devices requiring lower voltages, like 10 or 12 volts, utilize transformers to step down the voltage from the outlet, preventing damage.
  • Others argue that many modern devices may use pulse width modulation (PWM) to control voltage and current levels, rather than relying solely on transformers.
  • A participant questions how appliances with standard-sized plugs, such as can openers, convert 110 volts, suggesting they may not use the full voltage directly.
  • There is a discussion about the necessity of multiple voltage requirements in devices, with some participants suggesting that certain components would be damaged by higher voltages.

Areas of Agreement / Disagreement

Participants generally agree that devices require some form of voltage conversion, but there are competing views on the methods used, such as transformers versus PWM. The discussion remains unresolved regarding the specifics of how various appliances handle voltage conversion.

Contextual Notes

Some claims about the operation of specific devices, such as can openers and their use of motors or PWM, depend on the design and may not apply universally across all appliances.

Newtons Apple
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Hey everyone. I have a question. If we in the US have 110 -120 volts coming out of our house outlets, and we plug in a device that requires 10 or 12 volts... how does it not get fried? Do all devices have some sort of way of stepping the voltage down further to what it needs? Also I noticed that appliances like TV's and computers have more than 1 voltage requirement. For example, some have 1.1,3,3.5,12,and 15 volts? Why is this, does it switch voltages if it's not doing anything? Isn't 3, and 3.5 close enough? Why not just make the requirement 15 instead of all the smaller voltages?

Thanks!
 
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Newtons Apple said:
Hey everyone. I have a question. If we in the US have 110 -120 volts coming out of our house outlets, and we plug in a device that requires 10 or 12 volts... how does it not get fried?

Why do you think it doesn't.

Oh ... you probably think that because the DEVICE requires, say 12 volts, that the thing you plug in the wall requires 12 volts. It doesn't. It's called a transformer and it requires 110v in so as to convert it the the 12 volts that the device needs.

If you plug a 12v device into 110 volts with no transformer then you can bet that it will be fried.

Do all devices have some sort of way of stepping the voltage down further to what it needs? Also I noticed that appliances like TV's and computers have more than 1 voltage requirement. For example, some have 1.1,3,3.5,12,and 15 volts? Why is this, does it switch voltages if it's not doing anything? Isn't 3, and 3.5 close enough?

Yes, here you've got it. They all have transformers. Some have multiple-tap transformers so as to perform multiple step-downs.

Why not just make the requirement 15 instead of all the smaller voltages?

Because many devices, particularly semi-conductor devices, would be fried by 15v.
 
Ohh, I completely forgot that a lot of devices have the thick power plug. Now what about appliances that just have a regular size plug and not the big thick power plug? Looking at my can opener, the cable for it, is just the regular sized power cord. How do these convert the 110v ? I don't think a can opener uses 110 volts straight?
 
Newtons Apple said:
Ohh, I completely forgot that a lot of devices have the thick power plug. Now what about appliances that just have a regular size plug and not the big thick power plug? Looking at my can opener, the cable for it, is just the regular sized power cord. How do these convert the 110v ? I don't think a can opener uses 110 volts straight?

Why do you think it doesn't? a can opener is a motorized device, not a semiconductor device.

In any event, there can be transformers IN a device --- they don't have to be part of the power plug.
 
Some devices use the step down transformer, however most devices now use a process called pulse width modulation. By sending pulses you can control the current as well as the voltage levels. Some can openers can use a DC motor utilizing a PWM circuit.

here is a straightfoward circuit and covereage of PWM

http://www.personal.psu.edu/axl17/242l9.pdf

Their are numerous examples for different voltage/current conversions with PWM. Its also used for VFD's soft starters. Your home PC power supply etc
 
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