Question for JohnT

Someone posted about a commercial device to change 6V Dc power source to 12V DC. I wonder what the components inside would be. I understand Dc and Ac theory, but do not see how this could be done without changing Dc to Ac and then Ac back to Dc. This would be very inefficient and bulky.

Moonlite, "electronics" (versus tractor DC and AC power distribution) is NOT my cup o tea, its been too long lol

Wayyyyyyyy back in the old days with tube car radios a noisy humming Vibrator pulsed the battery DC and a step up transformer increased voltage BUT THATS WAY OLD TECHNOLOGY.

I cheated and found this article which describes DC to DC Converters as Linear or Inductive Switchers and it explains this muchhhhhhhhhhhhhhhhh better then I ever could.

Not to worry, since its an electrical question I'm confident you will get a ton of answers hopefully from some "electronics" experts who are more current then myself who can better answer or research the topic for you. I'm short on time I'm heading SOUTH today.

Sorry I cant help

John T
DC to DC Converters

moonlite37,
I'm not John T. As far as I know they broke the mold after he came along. Good man.

I have a 12v car charger that charges my 18v dewalt batteries. How can that happen you may ask?

It the same way 6v car radios that used vaccum tubes. They took 6v and made 150-300v DC.

Not to write a long answer, I'LL give you a KISS answer, Keep It Simple.

If you pulce DC into a transformer the transformer thinks it AC. Using a step up transformer you have a high voltage AC. Then using a rectifier you changed the AC back to DC. That's how it was done with car radios with tubes. Back then they had a tube that buzzed, vibrator tube, which switch DC on and off.

Today this can all be done with solid state components.

I read someplace where Green Line energy takes wind power in Kanas, AC, changes it into high voltage DC, Sends it to Ill where it's changed back to AC. Raymond James recommends a strong buy on this stock. So far it making 10% return on investment.

Hope I kept it Simple.
Geo

Good Neighbor George, to your statement "I read someplace where Green Line energy takes wind power in Kanas, AC, changes it into high voltage DC, Sends it to Ill where it's changed back to AC."

While I practiced more in LV Secondary power distribution, I did some HV transmission work, and YES high energy long distance transmission can be and is done the way you posted (DC Transmission lines) to limit losses...???.

Enjoy that new tractor

John T

(quoted from post at 07:16:06 11/05/19) Someone posted about a commercial device to change 6V Dc power source to 12V DC. I wonder what the components inside would be. I understand Dc and Ac theory, but do not see how this could be done without changing Dc to Ac and then Ac back to Dc. This would be very inefficient and bulky.

Click to expand...

"This would be very inefficient and bulky."

Some are quite tiny with efficiency in the 90+% range.

https://www.digikey.com/products/en/power-supplies-board-mount/dc-dc-converters/922?k=DC-Dc

John T
Elated with Hota.
It's my 401k tractor.
My 401 is making the payments. Zero interest.
George

"""switching power supplies""" made popular in computer power supplies and now in most all wall wart power supplies on others supplies. They are small, work well, but do have a current limit.

So yes,, the is a multi-vibrator circuit run with transistors to step up the voltage where its rectified back to DC.

Most of these can be rated at a amp or maybe a bit more in very small packages.

If you need lots of current, you need a large commercial grade inverter rated for your load.

https://www.ebay.com/itm/Aluminum-3A-36W-Automobiles-Step-Up-DC6-To-12V-Boost-Converter-Regulator-Module/292997893898?fits=Year%3A2012%7CModel%3AVolt&epid=19030129488&hash=item4438090f0a:g:4bAAAOSwMxBcglcF

I thought that was the reason Westinghouse pulled away from Edison, because DC could not be efficiently transmitted long distances.

What changed? Doesn't DC tend to heat the conductors and loose efficiency over distance?

I know just enough to ask dumb questions! LOL

I don't know the answer but since this involves electricity I couldn't resist the urge to post.

Steve its been too long since I read about this but it had to do with less reactive impedance when transmitting with DC versus AC ????????????? NO WARRANTY LOL I would have to study up on it again, but I do know its done and best I recall it was supposedly energy saving ????????????

Way back in the Edison and Tesla and Westinghouse feud it was figured transmitting at super high voltage at AC with less current was better then low voltage high current DC. They didn't have the DC to DC or DC to AC or vice versa technology and equipment in those days they have now. That's best I recall again nooooooooooooooo warranty lol

Im pressed for time today (heading South in RV) too busy to research it ??.

As always fun sparky chatting with you

John T

Steve you are right that Edison was for DC
What changed. Tesla was a game changer. Edison used low voltage DC. Low voltage, high current and power losses are greater than Tesla's higher voltage low current, Power losses, I square R.

Just my opinion about Green Line. Power grid uses Millions of volts. You get close you hear the 60 cycle buzzing. That's also 60 cycle electro magnetic fields linked to some types of cancer. LFEMF.

High voltage DC. No alternating low frequency Electro Magnetic field. Safer.

I'm no EE . Just my opinion.
George

I don't blame ya one darn bit, the more the merrier woooooooo hooooooooooo especially Legal or Electrical

John T

There are at least a couple of different ways to "step up" DC.

If the power requirements are small, a voltage doubler circuit may be used. What this does is to take a couple of capacitors and individually charge them up. The capacitors are then connected in series, giving an output voltage that's double the input.

But most DC-to-DC converters use a transformer, which has the often desirable feature of isolating the output from input. So it's necessary to invert the DC to AC, step it up through the transformer and rectify the transformer output. With modern miniature components, these devices can be quite small.

> I thought that was the reason Westinghouse pulled away from Edison, because DC could not be efficiently transmitted long distances.

> What changed? Doesn't DC tend to heat the conductors and loose efficiency over distance?

It's not true that DC can't be transmitted efficiently over long distance. You just have to get the voltage up, and that was the problem faced by Edison: He didn't have any practical way to step up or step down his DC power, while Tesla and Westinghouse could easily step up and step down AC using transformers. It wasn't until devices capable of switching and rectifying high voltage, high current power came along that DC transmission became practical.

In fact, high voltage DC is significantly more efficient to transmit than high voltage AC. Capacitance and inductance in the transmission lines aren't a factor for DC, and DC uses the whole conductor while AC tends to travel along the outside of a conductor. But the conversion of AC to DC and back costs a lot: the hardware is expensive and there are power losses associated with the conversion. So DC transmission is limited to fairly long distances, typically several hundred miles.

MarkB_MI,
I forgot all about including Impedance losses.
George

(quoted from post at 15:06:04 11/05/19) > I thought that was the reason Westinghouse pulled away from Edison, because DC could not be efficiently transmitted long distances.

> What changed? Doesn't DC tend to heat the conductors and loose efficiency over distance?

It's not true that DC can't be transmitted efficiently over long distance. You just have to get the voltage up, and that was the problem faced by Edison: He didn't have any practical way to step up or step down his DC power, while Tesla and Westinghouse could easily step up and step down AC using transformers. It wasn't until devices capable of switching and rectifying high voltage, high current power came along that DC transmission became practical.

In fact, high voltage DC is significantly more efficient to transmit than high voltage AC. Capacitance and inductance in the transmission lines aren't a factor for DC, and DC uses the whole conductor while AC tends to travel along the outside of a conductor. But the conversion of AC to DC and back costs a lot: the hardware is expensive and there are power losses associated with the conversion. So DC transmission is limited to fairly long distances, typically several hundred miles.

Click to expand...

At 60 cycles the "skin effect" is not a problem..

At frequencies much below 1 / {displaystyle 1/rho epsilon } 1/rho epsilon the quantity inside the large radical is close to unity and the formula is more usually given as:

= 2 {displaystyle delta ={sqrt {{2rho } over {omega mu }}}} delta=sqrt{{2rho }over{omegamu}}.

This formula is valid at frequencies away from strong atomic or molecular resonances (where {displaystyle epsilon } epsilon would have a large imaginary part) and at frequencies that are much below both the material's plasma frequency (dependent on the density of free electrons in the material) and the reciprocal of the mean time between collisions involving the conduction electrons. In good conductors such as metals all of those conditions are ensured at least up to microwave frequencies, justifying this formula's validity.[note 1] For example, in the case of copper, this would be true for frequencies much below 1018 Hz

What is the stock symbol? That's a great yield!

Just a few comments:

As others have said, switch mode power supplies have been around much longer than me, first as mechanical vibrators with either electrical or mechanical rectification, then with solid state devices. They are not new but offer some advantages over linear power supplies and are now very common with the advent of inexpensive components.

The few wall wart power supplies I have unpotted were all just transformers and rectifiers. I am sure there are some that use a switched mode power supply but I expect most are just older linear supplies.

I doubt there are any grid power lines using "millions of volts" AC current. Most are going to be 500K or less although there are a few DC lines that may reach a 1000K but I do not know if there are any in the US. There are some lower voltage DC lines in the US.

I have not seen any real studies that link 60 cycle magnetic fields from living under a power line to any forms of cancer. I would be interested to see any real peer reviewed studies that show that connection. A lawyer advertising on TV does not count as a medical expert.

The skin effect is real for 60 cycle current. Depending on the material the wire is made from the skin depth can be 3/8 of an inch or less. For high currents that depth becomes a problem. Power substations used to use hollow conductors at one time and maybe still do because of the skin effect at 60 cycles.

As Mark said, voltage doubler circuits were common at one time and were used instead of transformers in some low end radios and TVs. The basic circuit, a Cockroft Walton multiplier, was used to supply several millions of volts to early linear accelerators used for atomic research using essentially nothing more than diodes and capacitors.

With the advent of inexpensive power MOSFETs and IGBTs, these power supplies are very common and for good reason, they work well in a lot of applications.

> At 60 cycles the "skin effect" is not a problem.

Generally speaking, yes. But we are talking about heavy transmission lines that carry hundreds of amperes over hundreds of miles. A given size of conductor will carry more DC current than AC.