Any electrical engineers here?

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Ed S 2

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I have to interview someone in the eletrical engineering field for my english technical elective class here at University of Tennessee. I have about 15 short questions about reports thats you write for your job as an EE. Will take just a few minutes if I can help me out that would be great. I'll send an email with the questions to whoever can help. Hopefully some one here is in the EE field. Let me know

Thanks,

Ed Shouse
 
Ed if you cant find any thing I can ask one of the 10 EE's we have at work if they will help you..

Todd Z
 
I am, shoot me an email.
Click to expand...



Soot me now shoot me now.... Don't wait till I get home, Shoot me now !!!!..



Chops, I don't think licking 9 volt batteries counts..... :lol::lol:

Todd Z
 
That HAS to be from a movie Todd, it went over my head.....:lol:



9v batteries...been there many times. I got in trouble in the 7th grade for getting a circle of friends to hold hands while I completed the inductive path with a transformer and D cell batt...:cool::eek:
 
Actually that is a good line from a Daffy duck/ Bugs bunny cartoon......



I remember those circle days, we did BBQ igniter's and would charge up capacitors.....

HAHAHHAHA

The fun days...

Todd Z
 
Ed...I also work with several EE here and would be glad to help if needed. Always willing to help a fellow Tennessean.
 
"How important do you feel it is to increase the research needed to design a competent

automotive electrical system to handle the future anticipated requirements of newer

electrical systems that may require 24, 36, or even 96 volts, to supply power to the

new technologies that auto manufactures are planning on adding to their vehicles in the next

five to ten years?"

I'm not an EE, either, but I am currently working with 36v. systems (Hybrid) at my

job as a Quality Tech in Spring Hill, G.M.!



(If Saturn can do it, anyone can do it?!?!):blink::D
 
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That's a good question.



Here is another question that I posed to myself this weekend. I was in the newly remodeled kitchen of a friend. They did a great job, very clean and modern look. But over on a granite-topped counter sat a nice new wireless telephone base and it was connected to a power outlet through a fugly black-brick transformer plug.



So, as I considered this, I was struck by just how many electronic components in the average house run on 12v DC and various amps, and each of these components have their own transformers. Then I considered the extra cost associated with each of these products due to each having their own transformer, and just as important, all the heat generated by these transformers.



So, I considered the following question: Shouldn't we have a standard that more of these components could share (max amps?), and wouldn't a whole-house DC transformer and seperate circuits for the DC components be useful?



Now I know the history of DC vs AC in homes, and I know the safety issues associated, but I have to assume that no one could have predicted 100 years ago all the electronic components we run today.



Thoughts?



TJR
 
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But TJR....



'Had' you visited the newly remodeled kitchen that was just by chance, designed and installed by an EE, and say the electrical outlets were hidden by means of a commercial power strip tucked up underneath the cabinets-out of view and hidden to keep the tile/glass pattern continuity of the backsplash, would the same transformer considerations come to mind?

Or would that have freed up thought processes for other ideas?:lol:



[Broken External Image]:



Those are my first thoughts.



My second thoughts are, there would be a lot of appliances blown up due to cross polarity if DC circuits became popular with the average masses. And then there would be a conformity issue, I have things that require 5v, 9v, 12v, and 18v, and I don't have that much!

And there's the voltage drop issue-wire size vs resistance- each device would have to have voltage regulation to counter the high V+ required for long house runs.........

Solar is the future, DC may not be far off the mark. With any large solar power system, an inversion network (DC-AC Inverter) is required to run house appliances. How efficient is that? What if the inverter was not needed?
 
Yeah, there are ways to hide those bluky blocks...and I understand the challenges of DC throughout the home. But to answer some of your questions, that's where standards might come in. A max DC voltage of 18v or so might be sufficient, then the circuitry for stepping that down to 5v, 9v or 12v within the appliances is much more cost effective...heck a 7805 TTL chip is cheap, and can be made to support pretty high DC input voltages.



Hey, I was just brainfarting.
 
As an Electrical Engineer, I would love to see the questions that were asked, just for general discussion.



As for a whole-house DC system, there are several hurdles that need to be conquered first. One of the first things it the whol P=IV situation. The power requirement is equal to the current multiplied by the voltage. One device that draws 200mA at 12Vdc draws 2.4W. Not bad. But if you have a house full:



-PDA

-Cordless Phone

-Cell Phone Charger

-Digital Camera

-Answering Machine

-Computer Speakers

-DSL/Cable Modem/Router



all drawing an average of say 10W at 12Vdc, that equates to an average total draw of 70W, and at 12V, that means you need a device capable of handling 5.83A. For AC, no biggie. For DC, you need a transformer that is the size of a large toaster oven. Then you need to fuse each line to the wire size. In the kitchen and bathroom, DC is problamatic. DC and water don't mix well (course neither does AC) and can be much more dangerous than AC. THen you have the simple fact that DC does not really like AC hanging around too much. It's need all kinds of line filters and such especially when you have long runs. DC power will begin to pickup transient voltage spikes from AC systems, especially fans, air conditioners, computers, TV's and radios. God forbid if you have any kind of frequency drive in the house....



Linear Transformers are ancient technology comparatively speaking. There are new devices out that work quite well that are not much bigger than a choke on a power cable. They are just expensive right now in comparison. As EnergyStar and other regulations go further into effect, we will see the slow phase out of the Wall Wort as we know it now.
 
The best way to run a house on DC is to run at 96VDC. Then your power requirements stay about the same they are now.



Any engineer who has worked with MOSFET switchmode power supplies can then drop the voltage to 12, 24 6, ect... at the terminal where you are plugging your phone or what ever else you are running into the wall.



You would increase the efficiency of the home by taking the crappy low efficiency transformers out of everything from your computer to your alarm clock; keep AC on the outside, since AC is the best way to get power to travel long distances, put 1 super high efficient transformer and AC/DC converter on the outside of the home. Your fire hazards would also decrease since most fires in electronics originate from crappy transformers.



This would lower your power bill, greatly reduce the amount of electric field /magnetic field inside the home (for you feng shui types) and decrease the cost of electronic items since they no longer have to have their own on board AC rectifiers......



As far as noise on DC goes, DC has just as much noise on it as AC does. Less actually, but all that line noise gets eaten up in transformers on your AC line. Which would not be found on a DC line. The way to keep noise off of DC lines, is to keep the voltage up (again 96VDC), keep the impedence down, keep runs less than 100ft, do not daisychain too many outlets, proper bypassing at your terminals, and use TVS devices (transiant voltage suppression) on each of your power terminals. They are small, cheap, and work exceptionally well. Much better than a transformer actually, and zero power loss. The only power loss is from the noise being shunted.



Sounds complicated, but it is actually a lot less involvement than having 500 transformers and rectifier circuits in my home. Wall warts are transformers, but transformers are also in your computer, TV, radios, alarm clock............everything but your toaster.................



Ed, sounds like you have been helped, but if you need another response, I am an EE, so feel free to send me an email.



cheers,

 
That's what I was thinking too, AndyG....there is a a lot of extra cost, in the cost of transformers for equipment and lost energy due to transforming, and increased heat which means even more energy for cooling. Seems to me that a lower cost solution is to transform that AC to DC once for the whole house and go from there...and that transformer can be beefy and outside the home where heat is less of an issue.
 
What would also be nice about running at 96VDC... You wouldn't really need to worry about the incandecent lighting. The lightbulbs will light and have no problem. Now flourecent lights would be different story without changing out the ballast. I like the thought of a 96VDC house.... that's awefully intreagueing.



How much harder would it be for a device manufacturer to take 96VDC in and do the step-down in the device instead of at the the terminal?



Also, what do the other EE's think about PowerRF and similar type scenarios (that is, powering devices through an RF field instead of physical cord). In several manufacturing plants I have read about, all the PLC's, photoeyes and other LVDC sensors and devices are run much like RFID devices. It's definately cutting egde, but will it be the future of the home?
 

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