direct current is better than alternating current. Tesla and Westinghouse won the current wars, because it was easy to transform into different voltages without electronics, and they needed high voltages, which travel longer distances in smaller wires than low voltage.Our current system is based on big, central power plants like Niagara Falls shown above, that pump out high voltage (as much as 400,000 volts), step it down to 22 thousand volts for distribution at street level, then down to 110/220 for distribution to our houses. At every step, there are transmission losses; as much as 10% of the electricity transmitted by the power plant is lost on the way. The losses are higher in AC than in DC because it grounds so easily; according to the Economist, DC distribution is far more efficient. And then we get to our homes and offices.......where there is a 110VAC outlet every 12 feet on our wall, switched outlets in our ceilings, all feeding expensive copper wires back to a central panel. And what is plugged into almost every one?

Wall warts, transformers converting to a variety of voltages keyed to specific small appliances and electronics. For we now live in an electronic world, and almost everything we use other than vacuum cleaners and kitchen appliances are now running on DC Of course there is no standard of wall wart; every computer, lamp, radio or LCD TV has a different size and voltage. portable ac unit serviceAnd every wall wart wastes energy in the process.central air conditioner parts for saleLighting, now mostly incandescent needing lots of power, is going low voltage DC as we convert to LED and CFL; hvac air conditioner leaking waterevery fixture and even bulbs are filled with rectifiers and transformers to convert the power to low voltage, using resources in the manufacturing, and wasting energy in the operation.

For those who want to reduce their consumption and generate a little power of their own with a solar panel or wind turbine, standard practice is to run the 12 DC volt output through an inverter to change it to 110 AC for distribution through the existing 110V wiring. Of course the inverter is not 100% efficient and what are we doing at 90% of the electric outlets? Plugging in a wall-wart and converting it back to low voltage.When he was designing the MiniHome, Andy Thomson thought this was dumb, and chose all of his lighting to run off 12VDC, cutting off the transformers and wiring it directly to the batteries. He found a Creative sound system that ran at 12V and cut off the wall-wart. The inverter broke and he barely noticed, because everything in the joint but the microwave oven could run off 12VDC.The Google boys, Sergei and Larry, think this is dumb too. Engineers at Google, tired of running tens of thousands of computers with inefficient power supplies, have proposed a new standard for "high efficiency power supplies for home computers and servers" based on everything running on 12 volts only.

They say that it would save 40 billion kwh over three years, worth $5 Billion. Founder Larry Page complained about this last year: "I'm going to just plead with all of you, let's get the power supply problems fixed, or let's get all these devices talking together"John Laumer has noted here that 12 Volt appliances are easier to supply alternate emergency power if you are knocked off the grid by a hurricane or other disaster.It is time for our codes and our wiring to reflect this, shall we say, transformation. It is time for big steps:1) Develop a universal standard around 12 volt dc for all electronics. Enough of this silliness that makes every wall wart a different voltage. There will still be different sizes as there are different power requirements, but agree on one voltage.2) Develop a standard wall plug or distribution system for 12 volt DC. It is ridiculous that the only standard plug for this voltage is the automotive cigarette lighter.3) Provide a secondary wiring system in all new houses at 12V DC based on the new plug.4) Revise our current wiring codes to reduce the number of 110V outlets and circuits required.

Now most electrical codes demand outlets every 12 feet, in every ceiling, duplex outlets in kitchens. Copper is expensive and its mining is destructive; if there is 12VDC wiring then an outlet per room for the vacuum cleaner is all that is needed. That way, there can be dual systems in a house without any more copper than is needed now.12VDC power needs no childproofing, no wall warts, creates no EMF and makes adding incremental sources like solar and wind much easier. Let's make it the standard. Here's another take on the transformerless AC line power supply, which finds use in some well-insulated, low-power devices. Our technical reviewer pointed out that Cac should be an X-rated safety type, and I think we'd both feel better if the ground symbol wasn't there! SMPS circuits offer an efficient way to reduce AC from a mains source to any desired level for powering low-voltage circuits, though this comes at the cost of components such as control ICs, switching transistors, inductors, etc.

Figure 1 shows a simple way you can use more common components to step-down and regulate the AC mains to the desired low DC voltage. The reduction in AC voltage is obtained by dropping the unwanted extra voltage across a capacitor (impedance Z=1/ωC) Cac of suitable value and voltage rating. The remaining AC is drawn as rectified output through a diode bridge. So even though DC flows through the output circuit of the bridge, the voltage dropping series capacitor Cac sees an AC flowing in its remaining part of the circuit. The value of the capacitor determines the current output at reduced voltage. A larger capacitor is required for larger output currents. A bleeder resistor (1MΩ) is set in parallel with Cac to discharge it when the AC is disconnected. The DC after rectification and filtering is shunted by the Q1-based regulation circuit, which basically tries to maintain the output voltage within certain limits. 1 This step-down converter drops AC mains voltage across Cac to

produce a lower DC voltage. is optional and is related to safety issues – choose higher wattage if is the unregulated output which can be further regulated using chips like 7805/12 etc or a simple zener-transistor regulator. chosen according to power requirement – essentially it should be able to drain the unused current when the load is absent. of fuse are indicative – choose it according to your design/need. The circuit has two LEDs. The red LED indicates whether the power from AC is being used, or bled as waste through Q1. The green LED indicates the power availability at the output where further regulating devices can be added. R1, R2, and RB (R1,R2 » RB) form a voltage divider network which essentially monitors the residual rectified AC from the bridge. Their values are chosen such that when the current is flowing through the load (not shown), Q1 is switched off and hence little current flows through the second bleeder resistor RB, limited by the large values of R1 and R2.

The voltage drop across RB is not sufficient to turn on the red LED. At this point, we say the current flowing through R1, R2, and RB is the housekeeping current which constantly flows apart from the maximum load current. Q1 is biased by the voltage drop across R2, which should be at least 0.6V for Q1 to turn on. During normal operation (current flowing through the load), the values of R1, R2, and RB are chosen such that this voltage is less than 0.6V. However, if the load is disconnected (no output current is being drawn) then the voltage after the diode bridge will increase, which in turn will increase the voltage drop across R2 until the transistor turns on and draws current through RB. This stops the voltage from increasing further, simultaneously increasing the current through the red LED. A glowing red LED indicates power wastage. However, the green LED always glows when power is available at the output. RB should be chosen such that the rise in voltage at the bridge output during no load condition is within the upper limit of any final regulator connected to +VU.

The required capacitor Cac is calculated as: where IL is the maximum load current, Vrms is the RMS AC voltage, VE (~VU+1.2) is the residual expected voltage at the bridge input, which is taken to be the sum of VU and 1.2V across the bridge diodes. ΔIL is the house keeping current apart from the maximum load current. A rough estimate of Cac is IL / (ωVrms) (where ω = 2πfAC) as can be seen from the formula by neglecting ΔIL and VE, which are small compared to IL and Vrms respectively. This circuit offers an alternative to a bulky, noisy, vibration/magnetic field/heat producing transformer. However, the advantage of the transformer is in the isolation it offers from live AC. The danger with the proposed circuit is when Cac shorts out. Precautions should be taken to see that the fuse blows out before the voltage across the output rises to a hazardous level. Under increased voltage conditions, extra current paths are offered by the zener VUZ and the filter capacitor CF . Additional cheap neon lamps can be added across the bridge input to salvage the output regulating circuit and the load.