Here we are in section 6.5 and we're completing this chapter with a little discussion about alternating voltage applications. The devices that require alternating voltage is endless. if you think about all the different things that you can plug into an AC outlet and operate, the list is probably quite endless. Your text starts with a little discussion about 60Hz power distribution. This is referred to as industrial power, in fact, at the college here we have an emphasis in industrial power in our electrical engineering technology degree. Our students are inclined towards that subject area.
Water, coal or nuclear power are used to generate 60Hz AC. Usually generated at several thousand volts and transported across the country. Outside your home, it is dropped down to 220 and then to about 110. Now the actual values fluctuate 100 to 130. We typically say 120volts. This value is the RMS value. The peak value is 170 and the peak-to-peak would be 340 and remember when we looked at 120 if we divided that by 0.707, that's where we would get this peak value. Remember when we look at AC, this is the peak and from here to here would be the peak-to-peak. That's where we would get that. If we looked at an oscilloscope, at 120volts, that's what we would see.
Sound waves are made of sinusoidal pressure changes in the air. The frequency range for audible sound is from 15-20Hz to about 20kHz. Down here is where you, some of us can hear that low, some feel that, rather than hear it. This is very high, this would be the very high frequency. Sound waves travel through the air at approximately 1130 feet per second or roughly 1 millisecond per foot. Above 20kHz, we begin to lose the ability to hear that sound.
That brings us to ultrasonic waves, which start up with about 25kHz. Ultrasound waves are above the range of human hearing and have many applications including burglar alarms, range finders etc. Range about 25kHz to hundreds of kHz. There's just a multitude of applications for ultrasound. Many medical applications us ultrasound, for imaging equipment, without the danger of x-rays. many of our students, they go into the BioMed emphasis and they find employment in hospitals and some of the things that they repair are ultrasound equipment. Ultra or Oral Hygienist in dentistry also use ultrasound to clean teeth.
Lots of applications for ultrasound waves.
These are typically much higher frequency, radio or electromagnetic waves are used in a wide array of electronic devices. Typical applications for radio waves include, this is going to be radio/television broadcasts, and that would be over the air. As transmissions, but also I n this frequency range you see the cable also. Radar, uses radio waves, microwave communications, satellite communications, all of these are using RF. radio waves travel at this, 300*106 meters per second or 186,000 miles per second. The RF frequency range is from, technically, goes from down around 20Hz to hundreds of GHz.
However, most of the applications you see in RF are going to be in the MHz and GHz range.
Bluetooth is a global specification that defines a wireless technology internet to take the place of cables associated with computer systems and networks. Devices associated with Bluetooth have low-cost transmitters and receivers that operate over short distances. Keep in mind this is over very short distances, Bluetooth applications operate in the 2.4GHz to 2.4835GHz range. This is the range of Bluetooth. The range of these devices can be as short as 10 centimeters and it can be up to 100 meters.
Actually, there are three classes of Bluetooth devices. Your text doesn't get into it and most of the devices are going to be up to 10 meters or about 30 feet. Some of the applications that you see for Bluetooth are for example a wireless mouse can use Bluetooth, so you don't have to have the cable connecting your mouse to your computer. It will just connect wirelessly using Bluetooth. You'll notice it will be transmitting, it will be a relatively short range, so it doesn't... One of the values of Bluetooth is it transfers at such a short range that it doesn't interfere with other systems. Also maybe a keyboard to the computer could be wirelessly connected using Bluetooth.
One of the applications that we're seeing now is with wireless phones that actually have a Bluetooth connection. This is the wireless actually uses RF but with the part that we're talking about here is the, for example when you're driving your car and you want to talk on your wireless phone. Often times, they'll let's say this is you and you have a headset on, connected to your ear. Then you have something here connected to it so you can talk. Traditional wireless phones, you would have a cord that would run over here and connect to this. Then you would touch the buttons on your phone then have your conversation.
But with Bluetooth-enabled wireless phones, you wouldn't have this cable, no need for this cable. You could have that headset and your phone would connect to the headset via the Bluetooth connection so you wouldn't need to have this cable and walking around with it. Anyway, Bluetooth applications are becoming very popular and we'll probably be seeing a lot more of them.
Wireless Internet Links are designed to free users from the constraints of traditional telephone and network lines. Communications via a wireless network can be as much as 350 times faster than standard in-home connections. This is a quote from your textbook, and I'm just thinking, this must be compared to a very slow home connection. Because my experience with wireless Internet is, it doesn't, usually if you have a wired connection via either cable or T1, T3 or fiber or any of those, they'll be vastly faster than the wireless internet connection. Mind you, the wireless internet connections are usually faster than a dialogue modem, but I just think that this 350 times faster is a little bit stretching it.
But we'll see. As time progresses maybe it'll get better. Wireless internet can also be an integral part of Bluetooth devices and systems. This concludes our discussion of, or at least our introduction to alternating current. We've been looking at some of the applications that you can do with alternating voltages. We looked at wireless internet, we looked at Bluetooth, radio waves, ultrasound waves and sound waves. Then we also looked at the generation of AC for power distribution.
Video Lectures created by Tim Fiegenbaum at North Seattle Community College.
by Jake Hertz
by Robert Keim
by Jake Hertz