MECHANICAL DC/AC TRANSFORMERS

MECHANICAL DC/AC TRANSFORMERS

 

Years ago on YouTube, I was mesmerized by a device called either the “Joule Ringer” or a “Joule Thief.” Young hobbyists were lighting up 120 volt incandescent or fluorescent  light bulbs with nothing but a small 9  volt battery. Amazing! It was almost like free power! We could solve the energy crises!  As it turned out, they were just frying up transistors by pulsating (switching on/off) high frequency current. By using coiled wire around a magnet, they would apply voltage to coil (A) and (B).  that would build up an electrical field. See figure 1.

Figure 1

A NPN transistor is used as a switch to collapse the electrical field. Once the induction of the coil saturates, the circuit basically created a short across the transistor that would force the emitter side to switch off, causing the electronic field to collapse.  For an instant, a voltage dump stronger then the originating voltage resulted: a lit LED light bulb with a “dead” battery! This cycle repeated itself so fast that the human eye cannot see the pulsating on/off again current, thus overheating their transistors. So, for example, a weak 1 volt battery could deliver 2+ volts, but only for an instant, a millisecond. This extra voltage was not “free,” just sacrificing a time interval to bump up the voltage before the discharge (frequency).  The hobbyist became really creative with larger coils, the use of capacitors (similar to a coil), and sneaking in larger batteries but on a whim, just say they were very small hobby batteries. They were running and lighting 120 volt appliances all over the house, so they have you believe. But in the end it all comes down to power, the watt, you will not run a hair dryer on a 9 volt battery; but it was cleaver tomfoolery based on the concepts like the Tesla Coil.

The “Joule Thief” was nothing but a simple transformer, similar to a DC Boost Converter by introducing frequency (Hz) into a DC circuit. In a functioning industrialized world, we have step down AC transformers everywhere, all around us! They are in our phones, our laptops, I-Pads, TVs, EVERYTHING. Why? Because we have to step down high voltage alternating current to simple DC low voltage for our electronic devices. But transformers only work with alternating current right? No. Any disruption in current can create a pulse thus collapsing the electromagnetic field to step-up or step-down current, (interrupted DC current).  U.S. cars back in the 1970’s used mechanical breaker points to increase voltage for the ignition system, we called this the “coil” but it was just a transformer. Henry Ford used a vibrating solenoid with  reed contacts to break the circuit for his Model T automobiles. Today we use transistors, like the “Joule Thief” in the modern automobile. See Figure 2.

Figure 2

Back in the 1920’s when the first radios were sold, a mechanical transformer, “Vibrator Power Supply” was used to create AC current in rural area that had no line power. To power the heating elements in a vacuum tubes, alternating current was required so the homeowner would hook up their 6  volt “car battery” to this buzzing power supply just to listen to the radio. The Vibrator Power Supply was not reliable. The contacts would burn out or the reed switch would fall out of alignment. See Figure 3.

Figure 3

 Basic Transformer Introduction

I am a mechanical engineer, not electrical, but I know some basics and will keep this very basic and simple. Transformers are the backbone of the modern industrialized world. They are only useful if 1000+ ton steam or water powered turbine generators around the world are pumping out well over 200,000 volts across a network of miles of cable every second of the day. All modern devices are designed to run off this cyclic high voltage residential power but stepped down to 120 volts for residential power. Electronic devices require a rectifier to create low voltage direct current while home heating and cooling require alternating current straight from the power line transformer. See Figure 4

Figure 4

First the Terminologies: A “transformer” is generally used when stepping up or down AC, (alternating current), voltage that has an iron core with coiled copper wire. A “coil” is often used if there is no iron core, just air as a core and just coiled copper wire. Examples of a “coil” are the Tesla Coils, or the automotive coils (that uses oil not air), and as stated above the Joule Thief, or “Boost Converters”. They all do the same thing. They all build up a magnetic field then collapse it to either alter the current or increase frequency (Hz) to induce current. As I will demonstrate later, a “transformer” can be used as a DC Boost Converter, or a miniature Tesla Coil, if my frequency is high enough (magnetic resonant).

Electricity is basically a simple magnetic field produced by the flow of electrons in a wire. See Figure 4. In direct current, (DC), the magnetic field rotates clockwise around the wire from negative to positive a continuous voltage. See Figure 5, Example 1. In alternating current, (AC), voltage cycles from negative to positive in reversion directions due to the armature of the generator spinning in and out of a magnetic field into the field positive direction, then out negative direction. See Figure 5, Example 2. AC creates a cyclic voltage (sign wave) that can build up a magnetic field then collapse it. In a DC circuit, if the voltage is interrupted, voltage can build up a magnetic field in the coil then collapse it again.  See Figure 5, Example 3.

Figure 5

Coiling wire amplifies the magnetic effect on the adjacent wires. See Figure 6, Example (A). If this magnetic field surrounds a metal core, the axis in the iron atoms will align to the field further increasing the field. See Figure 6, Example (B).  The atom alignment in the iron core will be constant on both sides of the core. If the primary coil pulses a magnetic field, the secondary coil will also. If the winding were identical on both sides, the voltage will be identical less a small amount of internal resistance. To step up voltage, increase the field winding on one side,  but you will lose some amperage. See Figure 6, Example (C).

Figure 6

What If A Survivalist Needed High Voltage with No Power Grid?

If we are off the grid then all we have is DC, low-voltage current; 36, 24 or 12 volts taken from batteries. If a gas generators were utilized, this will provide 120 volts worth of alternating current but at the cost of running a generator continuously with an endless supply of a fuel and needed parts for maintenance parts. So for high voltage, we will need a transformer, or a motor/generator, (DC to AC), setup for short bust of power like for a welder or to pressurizing a deep well tank. Solar panels have a duty life of over 30 years. Well build DC motors with spare parts, (bearings and brushes), can last over 30 years depending on the load. Well built Nickel/Iron batteries are known to last over 100 years. If there are abandoned automobiles there would be an endless supply of spare parts consisting of copper wire, 12 volt electric motors and bearings. So, why not use a integrated rectifier to convert DC to AC? First, (1), you would have to own one at the time of a crises, (7000+ watt heavy duty inverters are expensive); (2), they tend to fail and are not reparable; and (3), EMP natural or man-made will fry any integrated circuit.
For demonstration purposes, I will illustrate how to amplify 5 volts to 47 volts by simply using a small radio AC laminated core transformer and a micro DC motor. As shown above, figure 4, this is a small step down transformer from a residential power source: 120 volts AC 60 Hz. to just 12.6 volts AC (milliamps). Since this transformer is designed for a low powered devices, it is small. With no line power, I will have to pulse a DC current to “transform” low voltage to high voltage. I will reverse the intended use of this device and supply low voltage to the secondary coil so to attain a higher voltage on the primary coil. In place of using a reed or point switch assembly as stated above, I will simply modify a secondary motor as a generator by disconnecting one of the three stator coil so the DC current will pulse. See Figure 7

Figure 7

Connect one motor by coupler to the modified Pulse, (square wave), Generator. See Figure 8. Attached a 12v DC power source to the motor and then from the generator attach power to the secondary side of the transformer marked in this case, 12.6 volts. Generator output voltage will be around 5 V at  600 Hz. From the primary coil of the transformer, the step up voltage will be around 47 VAC at 376 Hz. Using a 120 volt household LED, rated at 1.5 watts, will produce a bright light. See Figure 8

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Figure 8

 

 

Figure 9

 

Conclusion:

In the 1920’s through the 1950’s electronics consisting of electron tubes relayed on AC current. All integrated electronics today are powered by DC current alone. In a survival situation, the transformer wall plug-in would be bypassed by cutting the wire after the transformer and we would hook up to the rated DC voltage and amps output listed on the transformer case to a battery array at that rating. If a device you wanted to power only accepted AC current at 120 volts, yet required only a small load, then using a simple small motor/generator combination, reed switches, points, or a pulsation current similar to the example above can be used. You will waste a tremendous amount of power to run a 800 watt or 1,2000 watt integrated inverter to power only one 120 volt device at 1 watt. The more reliable and serviceable a voltage regulator is, the greater duty life to the devices you want to power.

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