November 12, 2012

Powering a low voltage DC load from a single-pole High Voltage power supply

Filed under: To blow your mind — VIP @ 01:33

Warning! High Voltage experiments possess a potential danger of electrocution and fire. Please be cautious when performing those experiments. Children should be supervised by an adult when experimenting with high voltage. High voltage can cause undesired electromagnetic interference. This interference can cause pacemakers and other medical devices to malfunction.

As a conclusion to the line of experiments single line power transition I want to showcase a device that caused a small electric DC motor to rotate by utilizing energy that was obtained through a single power line. The Avramenko Fork cannot generate enough power to run the motor constantly from the supply that I have.

Therefore I employed a crowbar circuit it that discharges a electrolytic capacitor and powers the motor only when the voltage in an electrolytic capacitor is above 5V. The motor runs for about five seconds and then the circuit recharges for about a minute; than the same thing happens again.

Some very nice people helped me design a thyristor crowbar circuit that would discharge a capacitor through a motor when enough voltage had accumulated in a capacitor. So the overall circuit looks like this:

  1. D2 is some Zener Diode that I happened to have that is rated to discharge at 5.1V.
  2. D1 is a NTE5455 Thyristor
  3. D3 and D4 are simple ‘1n something’ radio-frequency rectifier diodes. No high voltage diodes are required because this circuit opens at voltage that is higher than 5.1 volts.
  4. R1 is 100 Ohms
  5. R2 is 100 Kilo ohms
  6. R3 (The Load) is a 9VDC electric motor that was used to move the drawer of a CD-ROM.
  7. C1 is probably 100pf, but the circuit works well without it.
  8. C2 is a Rubycon 6.3 Volt 5600 Micro Farad Electrolytic capacitor.

    The frequency of this circuit switching a motor load on depends on C2, but there is no linear relationship between capacitance and the time it takes to charge.

    I think that some other qualities, such as internal leakage and lead resistance may contribute to that.

  9. I also connected another diode across the load since it is an inductive load and can produce voltage spikes of its own. I had used the same diode as in D3 and D4 for that purpose. (Not on the circuit diagram.) Make sure that you connect the diode so it does not conduct when the load is energized.

At this point the circuit is probably not safe for powering loads that have ICs in them since high voltage is pulsing throughout the DC circuit and can probably destroy fine electronic components. The motor can shock you if you touch it.

I hypothesized that introducing Q-loops into the circuit can prevent this voltage from conducting through a circuit and making it safer to use.

Q-loops may need to be placed before or after the electrolytic capacitor. I will need to measure the frequency of the high voltage power supply to choose the right values for the induction and capacitance in the Q-loops.

This is how the hypothetic circuit may look like.

The Avramenko Fork

This picture shows the way I had placed diodes in my circuit, but I may be wrong.

Electrolytic capacitors seem to leak and prevent high voltage from building up inside them, even the voltage they are rated for. I would try to build a circuit that involves high capacitance ceramic capacitors in the future and see how they perform.

I had connected the circuit with a motor to the single-pole power supply through a ceramic capacitor within the single wire ‘circuit’ and noticed that it happens to pulse the motor about as often as when the circuit was connected to a single pole supply with a solid wire.

Vladimir Tolskiy.


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