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Battery Operated Light

Discussion in 'LEDs and Optoelectronics' started by Dustin Smith, Jan 8, 2013.

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  1. Dustin Smith

    Dustin Smith

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    Jun 27, 2012
    Hi, I've been working on a circuit that uses batteries to power White LED's. I have solar cells set up to catch the side light of those and produce a bit more power to be used. I view it as recycling some of the used energy. I've tried to add this to the battery power, but this failed. I've since run it through a joule thief circuit to power one more White LED. This method is working.

    Q1: Is there a way to add the power of the solar cells to the battery power to reduce the power taken from the batteries, or to boost their voltage by adding it in series?

    Q2: I noticed two different joule thief circuits. One using a torrid and one using resistors and transistors with no torrids (so it looks like). Which one is better for my circuit?

    Q3: Any other ideas what I could do with the small extra power produced by the solar cells? I'll post some numbers later, I have to go for now.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    1) That's theoretically possible but with a lousy efficiency.
    2) I don't know the one without toroids. Note that a joule thief is usefull to squeeze the last drop of juice out of your battery. It is by no means an efficient step-up converter.
    3) Yes. Forget about recycling the "side light". This goes in the direction of a perpetuum mobile (use electricity to generate light to generate electricity to generate light...). Dissent from some unteachable people aside, it has been shown that this kind of machine is impossible. My tip: use a better collector or reflector to use all of the LED's light. You may then be able to reduce the current and extend the lifetime of your battery.

    Harald
     
  3. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Last edited: Jan 8, 2013
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Chris,
    let's see his answer. In my view that other thread isn't exactly about joule thiefs, but he may have gotten that notion...
     
  5. Dustin Smith

    Dustin Smith

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    Jun 27, 2012
    Dear Harald,

    Here is an example of a joule thief with no torrid. I believe the orange componet is an inductor, (though I admit I'm guessing and I don't know what they do at this point. I will be reading up on them shortly though.)
    http://www.instructables.com/id/Joule-Thief-use-LEDs-with-only-one-AA-battery/]
    I have not tried the circuit.

    As for it being a step-up converter. (I had to look that one up.) I'm still not sure if a step-up converter is the same thing as a step-up transformer, but from my understanding it's an iron core with two wires wrapped to create a voltage ratio difference. I guess since the joule thief torrid has equal wrappings of wire, it is not the same thing. Is this right? This poses a new question for me though. Why/How does the joule thief torrid boost the voltage since the wire wraps are equal?

    As for the reflector idea, I think this may be a more viable way of thinking. Originally, my idea was to use solar cells near my CFL and T-5 bulbs, as they have light reflecting onto the ceiling. I was thinking, what a waste, I should recycle that. So I decided to try it out on a flashlight idea first. Perhaps I should be designing reflectors for my house lighting. My original purpose was to see how I can reduce the power usage of my household lights. Perhaps with reflectors, I can use lower wattage bulbs and achieve the same light needed in my living and working spaces thereby achieving my goal.

    Dear Chris,
    I appreciate the time you took to try and understand what I'm talking about. Although the Easter Engine was not known to me, it is now. It has sparked my interest. I picture an Easter Engine being used to wind up a device (such as a wind up toy/clock) and then I can take the fully wound device and use it's stored energy when I need it, perhaps. I'll have to work on this project later though, I have started too many things!

    Thank you both for your time. Feel free to expand my knowledge at any time. I hope I can expand your knowledge as well.

    Mr. Diedel
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    = toroid in this context. The difference being that a toroid is wound on a doughnut shaped core whereas the inductor used in the circuit is seemingly wound on a rod shaped core.

    A step-up transformer is a transformer where the primary coils has less windings than the secondary coil and where (usually) primary and secondary are isolated. An AC signal appliae dto the primary coil is output as Vs=ns/np*Vp where Vs, Vp are the secondary and primnary voltages respectively and ns, np are the number of secondary and primary windings. The transformer must be operated using AC!

    A step-up converter usually converts a DC input to a DC output by means of a switch mode power supply. Basically this involves chopping the DC input signal to get an AC component and use inductive components to step-up the resulting AC. There are also capacitor based realizations without inductor.

    The Joule thief used the flyback voltage that is generated by interrupting the current supply to an inductor. The energy stored within the inductor produces a voltage spike across the inductor when the magnetic field within the core breaks down. This voltage can rise to considerable levels if there is no path for discharging the magnetic energy. That is why a low input voltage can generate a high output voltage in a Joule thief. But the technique is not very efficient.

    Therefore I think it is a better idea to make the most of the light output from the lamp fixture (e.g. directing the light to where it's needed using reflectors). Then, if the light is bright enough where it's needed, you can reduce the light output of the lamp and thus the input of electrical power to the lamp.

    Harald
     
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Harald, it appears that you were correct. No connection to the Solar Engine circuit at all.
    BTW; nice TOO of his two circuits.

    Chris
     
  8. Dustin Smith

    Dustin Smith

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    Jun 27, 2012
    Inductors, Joule Thieves and Switched-Mode Power Supplies

    Harald,

    Let me say this back to you to see if I've understood what you're telling me and what I've learned from researching what you've posted.

    Firstly let me announce that I learned the word toroid simply means (in mathematical terms) a doughnut shape. On a further note, if you misspell it as torrid, you'll be looking at women's clothing! HA HA!

    1. With that being said, an iron-ferrite toroid wrapped with one wire is a type of inductor. An inductor (also choke, coil, or reactor) is a passive two-terminal electrical component that stores energy in its magnetic field.
    Question: Is an inductor only for A/C current?

    2. The iron-ferrite toroid in a joule thief circuit is an inductor with one additional wire wrapped alongside the first one. Instead of allowing the electricity to flow through the wire that created the magnetic field, it sends the electrical current through the second wire. Therefore they do the same thing by storing energy in a magnetic field created by the component. I don't see why we can't call the joule thief toroid a four terminal inductor. Or unless an inductor cannot use D/C current, perhaps we could call it a D/C inductor.

    Your point to me seems to be that using an inductor or "4 terminal inductor" (maybe there is a real name for this component, but that's my name for it for now) is less efficient than using a switched-mode power supply. In contrast to the switched-mode power supply, the joule thief I believe can be called a linear power supply whereas more energy is lost to heat as apposed to the switched-mode which has minimal energy to heat losses. PHEW! Man I hope that's right!

    SO.... If I want to use any circuit or device to boost my voltage and minimize my energy to heat loss, I should use a switched-mode power supply.

    Question: Just how much more efficient is the switched-mode power supply than the joule thief circuit anyways? I know how to build joule thief circuits, and my brain hurts from understanding all this right now, HA HA HA.

    P.S. Should I have started a new topic? This is far off from my original posting.
     
  9. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Yes, we call it a 'Transformer'. :D In this case a 'Toroidal Transformer'. ;)

    Chris
     
  10. BobK

    BobK

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    The toroid with 2 windings in a Joule Thief is used for 2 purposes: Its primary is the inductor in standard boost converter. The secondary is used for feedback to make the circuit oscillate. Thus, the two functions (oscillator + boost converter) are performed by 1 transistor, which is as close to minimal as you can get.

    In no way is it a linear converter. It is a true switch mode DC-DC boost converter, with a very clever design. I don't know what the actual efficiency number is, but there is no significant loss due to heat, so it should be quite high.

    Bob
     
  11. Harald Kapp

    Harald Kapp Moderator Moderator

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    Chris:
    please help me along: What do you mean by "nice TOO of his two circuits."? It's not in my dictionary.

    Harald
     
  12. Harald Kapp

    Harald Kapp Moderator Moderator

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    Dustin:
    Right. Toroid=doughnut shaped.

    add 1) An (ideal) inductor is an AC impedance. It has no influence on DC. A real inductor may have an influence due to parasitic effects like e.g. saturation and internal resistance.

    add 2) Joule thief is the moniker for the complete circuit consisting of a transistor, the transformer (or inductor, depending on the detailed circuit) and some other components (resistors, capacitors). A transformer alone makes no joule thief.

    A switch mode power supply is generally spesking more efficient than a joule thief, but the eficiency is a function of the power supplied by the supply or used by the load respectively.
    For small quantities of input energy you should lok up "energy harvesting". There are special circuits to draw energy from small energy sources (e.g. the stray light of your lamp harvested by a photovoltaic cell).
    However, if you take into account the energy needed to produce the chip, the other components, the PCB plus the energy required to manufacture the circuit, you may as well burn some coal to light your lamp a bit less efficient.
     
  13. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Sorry about that Harald. TOO = Theory Of Operation.

    Chris
     
  14. Dustin Smith

    Dustin Smith

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    Jun 27, 2012
    :D That made me giggle! he he he Thanks for your input. This has become more for my educational purposes than practical use to tell you the truth. Well, unfortunately I have to work now, everyone have a great day and thanks for your assistance. I'll be back in another thread with more questions..........
     
  15. Dustin Smith

    Dustin Smith

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    Jun 27, 2012
    Yes, I was looking around for your "TOO" too! ha ha.
     
  16. Harald Kapp

    Harald Kapp Moderator Moderator

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    Thanks, Chris, for the explanation. I'll try to remember :D
     
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