Paul suggested this Wikipedia article. I quote:
I remembered these, having seen one in action, and always wanted one. I think you might be interested. Perhaps that is why I am interested in JTs. There is more than a simple parallel.
When I was a kid, one of my dad’s customers died and his widow made my dad an offer that he couldn’t refuse: she would sell him all of her late husband’s tools and supplies – a whole shedful, for a very reasonable price. So my dad bought all of this plumbing tools and supplies and brought the stuff home and filled our shed to the rafters with the stuff. Being a curious kid, I started playing with this stuff, everything from pipe and fittings to the pipe threader and pipe wrenches of course. I became an amateur plumber. I also became fascinated with the things I could do with the pipe and fittings and a garden hose that supplied water. Soon I had built a lawn sprinkler and put enough pipe and fittings together to outfit a house.
My dad’s barber shop was a few doors down from a used book store. He used to take me over there and let me pick out some books, things like science books and books about dinosaurs and such. He perused the magazines and always managed to find a few Playboy magazines for his barber shop.
One book that fascinated me was a book on how things work. Things like steam engines (it was a very old book) and electrical generators and internal combustion engines and the pulleys in a block and tackle, and how the dam causes the reservoir to build up enough pressure in the penstocks to turn the turbine, which drove the generator, which powered a whole city, and on and on. One thing that I learned about was a hydraulic ram. Since I had this experience with plumbing stuff, I thought that it might be cool to build one, but I could never find the check valves and other special parts to make one.
Is a hydraulic ram the mechanical equivalent of a Joule Thief?
Many times I and others have used an analogy to show how an electronic device worked. The Wikipedia article at the end compares the Joule Thief to the hydraulic ram, and if you click on the talk tab, the discussion gets into greater detail on the comparison (but I haven’t read much of it yet). One thing I am certain of, the hydraulic ram puts out a more or less steady stream of water, because of the storage tank. The conventional Joule Thief does not have the electrical equivalent of a check valve and a storage tank. The JT would need to have a diode and capacitor added to the output between the transistor and the LED. The LED is a diode, but the voltage doesn’t reverse polarity and the LED gets intermittent pulses of current. I guess you could compare it to a hydraulic ram without a tank and just a nozzle which squirts out a stream each time the valve closes. These pulses would be roughly equivalent to the pulses of light from the LED.
I think it is like. JT because of the inertia of the water being analogous to the inductor field magnetic field ‘wanting’ to keep the current flowing steadily and the way it shuts off as the flow has increased. It uses something simple to turn low pressure high flow into higher pressure low flow. They are intriguing to see in action.
I have always wanted a stream running through my garden (not too close to the house though!). But, I think dud batteries are in a more plentiful supply as a source of free energy.