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Chemical reaction

All batteries are just little chemical factories. Usually two compounds (lead & acid, nickle & cadmium, etc.) are in proximity to each other and there are two electrical connections, anode and cathode. If a wire connects the two connections, the compounds exchange electrons from one to the other. The electron flow is determined by the elements so it's a direct current. Add current to the wire (charge the battery) and the process reverses, although not perfectly.

I believe that Thomas Edison and George Westinghouse competed on the issue of using direct vs. alternating current. AC won.

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It was actually Tesla who pushed AC. When Tesla was going belly-up, he gave his patent to Westinghouse who knew how to run a business. Even though it pissed Edison off to no end that a former employee was right, AC won over Edison's DC in the end.
 

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It was actually Tesla who pushed AC. When Tesla was going belly-up, he gave his patent to Westinghouse who knew how to run a business. Even though it pissed Edison off to no end that a former employee was right, AC won over Edison's DC in the end.
Edison was so pissed that he invented old sparky to discredit Westinghouse and to show that AC was way more dangerous than dc.


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It was actually Tesla who pushed AC. When Tesla was going belly-up, he gave his patent to Westinghouse who knew how to run a business. Even though it pissed Edison off to no end that a former employee was right, AC won over Edison's DC in the end.
A very contentious fight. Edison was very egotistical and hated to be wrong. While DC is more efficient, Tesla understood DC could not be easily transferred over hundreds of miles to reach the multitudes, of course Edison knew his patented substations would be required all over the US....money, money, money
 

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Edison was so pissed that he invented old sparky to discredit Westinghouse and to show that AC was way more dangerous than dc.


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Remember seeing videos of him demonstrating the effectiveness of electrocution by killing elephants? That wouldn't go over so well today...
 

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It was actually Tesla who pushed AC. When Tesla was going belly-up, he gave his patent to Westinghouse who knew how to run a business. Even though it pissed Edison off to no end that a former employee was right, AC won over Edison's DC in the end.
Edison was so pissed that he invented old sparky to discredit Westinghouse and to show that AC was way more dangerous than dc.


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Did you know that Edison actually hired people to kidnap peoples pets and bring them in to 'experiment' with?
 

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Might be alittle of topic, but does anyone find it funny that everything is brought to a home in AC and now with the wave of electronics it is being converted to DC.....
 

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Might be alittle of topic, but does anyone find it funny that everything is brought to a home in AC and now with the wave of electronics it is being converted to DC.....
Not at all. If you think about the most efficient way to generate electricity is either by moving a coil of wire around in a magnetic field or to move a magnetic field around inside a coil of wire. Either way you end up with AC.

The next step is to transmit the power. AC is much more efficient at moving power over long distances. DC requires much larger conductors. Also power generating stations need to be much closer to where the power is needed.

The last step is to convert the AC to DC that all of our gadgets love. To do this at the end of the line is way simpler and can be done with smaller components than if the AC to DC was done at the power station at high voltages. Takes is a small step down transformer to convert the 120v down to 12v AC. Then 4 small diodes can be used in a bridge rectifier to turn the AC in to DC.
 

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I'm looking forward to when homes will carry 12VDC through the walls just like we currently have 110VAC... Then, things like LED lights will be dirt cheap because we will be able to use them WITHOUT each light needing to have the power transformer built into it...
 

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Something around "36V" (which would mean 30 to 44 volts so that batteries could be used) would be nice. Above 50V the switching semiconductors are not as efficient and the caps needed are more expensive. You can also get a little "tingle" above 36V. You can string a bunch (8-9) of leds together and then regulate the current for the intensity so you share the efficiency hit of the current sense resistor over several LEDs.
A few challenges are we need a "standard" fixture for LEDs that can also get rid of heat. Ideally, the electronics would be elsewhere too. The switch would have to connect to the electronics since DC things don't like to switch off like AC things (long term arc damage to terminals). The win here is everyone wants to control their lights via some device, and it's getting cheaper to do so.

So in this wonderful world run by the 'M"s (Money, Management and Marketing) the challenge is not technical. Agreement on the concept of a box to power the lights that can be access via a network, a light fixture that gets rid of heat so you actually get 80K hours of life, and an economical way to do "small areas" that in the past had one or two 60 W incandescents is needed. Between patent battles, pride, and trying to sell this in a world where price is the #1 criteria, I'm not optimistic. When this problem is solved some day, it's highly unlikely the solution will come from any US company. Sad.

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Something around "36V" (which would mean 30 to 44 volts so that batteries could be used) would be nice. Above 50V the switching semiconductors are not as efficient and the caps needed are more expensive. You can also get a little "tingle" above 36V. You can string a bunch (8-9) of leds together and then regulate the current for the intensity so you share the efficiency hit of the current sense resistor over several LEDs.
A few challenges are we need a "standard" fixture for LEDs that can also get rid of heat. Ideally, the electronics would be elsewhere too. The switch would have to connect to the electronics since DC things don't like to switch off like AC things (long term arc damage to terminals). The win here is everyone wants to control their lights via some device, and it's getting cheaper to do so.

So in this wonderful world run by the 'M"s (Money, Management and Marketing) the challenge is not technical. Agreement on the concept of a box to power the lights that can be access via a network, a light fixture that gets rid of heat so you actually get 80K hours of life, and an economical way to do "small areas" that in the past had one or two 60 W incandescents is needed. Between patent battles, pride, and trying to sell this in a world where price is the #1 criteria, I'm not optimistic. When this problem is solved some day, it's highly unlikely the solution will come from any US company. Sad.

Pete
I'm going to go out on a limb and say that these points had a lot to do with why telephone wires were set up to carry 48V.
 

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I'm going to go out on a limb and say that these points had a lot to do with why telephone wires were set up to carry 48V.
Ringing current for your home phone is 105v.

Yes Dial tone is 48 v
 

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I'm looking forward to when homes will carry 12VDC through the walls just like we currently have 110VAC... Then, things like LED lights will be dirt cheap because we will be able to use them WITHOUT each light needing to have the power transformer built into it...
That is a brilliant idea! Most of the led failures are due to their power supplies I think.
 

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That is a brilliant idea! Most of the led failures are due to their power supplies I think.
The problem is voltage drop. It doesn't take much of a line run to drop the voltage by a good bit. This is why many of the better quality cctv security cameras work off of 24v AC. Many of the POE, power over Ethernet, things such as wifi access points and voip phones are switching to the newer 802.3at standard. When an 802.3at device connects to a network it picks up a low voltage signal from the power supply. It uses this minimal supply to negotiate it's power requirements with the supply. In the process the supply figures out what voltage it needs to send to make the object at the other end happy, this can be as much as 48v DC. The problem is all this cool active circuitry is way more expensive than a simple capacitor dropper circuit found in many of today's LED light fixtures.
 
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