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81CommentsNorfolk, VirginiaJoined November 1st, 2011
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  • shomas commented on krmartin3's instructable DC Boost Converter2 months ago
    DC Boost Converter

    True efficiency > 100% is like a unicorn. it is nothing more mythical and does not exist. Sure, some times we have apparent efficiency that are over 100% but the extra energy comes from something else and was not not accounted for in the apparent figure. thus the difference between true and apparent efficiency

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  • $1 DIY Conductive Ink and Paint From Fire! (non Toxic, Homemade, Cheap)

    "Those are unecessary safety concerns, in my opinion" When it comes to the potential of starting fires, the current density through a cross section of any conductor is very much a necessary safety concern made all more important by the fact your dealing with paper substrate and thin wires in one and or two dimensions made from inks. "You don't need conductive ink or paper to make a housefire using electricity." My point was not what is the best way to start a house on fire, but to bring awareness that the potential is real with poor designs, so that one can ensure it does not happen by accident. Simply put some thought into ones design.

    "Those are unecessary safety concerns, in my opinion" when it comes to the potential of starting fires, the current density through a cross section of any conductor is very much a necessary safety concern. made all more important by the fact your dealing with paper substrate and thin wires in one and or two dimensions made from inks. "You don't need conductive ink or paper to make a housefire using electricity." My point was not what is the best way to start a fire, but to bring awareness of the potential is real with poor designs so that one can ensure it does not happen by accident.

    "How concentrated would the Sodium Hydroxide have to be to dissolve the glass or silica gel, and how hot?" Concentration may very. Too low concentrations of sodium hydroxide will will not convert all the silicon dioxide into sodium silicate. Higher concentrations of of sodium silicate will take on more of the properties of sodium hydroxide. The reaction occurs very very slowly at room temperature. It happens much faster on a stove. "Would it be necessary (or advisable) to do this reaction in a fume hood, or at least somewhere with very good ventilation?" I dont believe anything is gassed off but for other safety reasons I would prefer doing it outside away from things. "Also, would any special protection be needed, over and above saftey glasses and gloves resi...

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    "How concentrated would the Sodium Hydroxide have to be to dissolve the glass or silica gel, and how hot?" Concentration may very. Too low concentrations of sodium hydroxide will will not convert all the silicon dioxide into sodium silicate. Higher concentrations of of sodium silicate will take on more of the properties of sodium hydroxide. The reaction occurs very very slowly at room temperature. It happens much faster on a stove. "Would it be necessary (or advisable) to do this reaction in a fume hood, or at least somewhere with very good ventilation?" I dont believe anything is gassed off but for other safety reasons I would prefer doing it outside away from things. "Also, would any special protection be needed, over and above saftey glasses and gloves resistant to hot Sodium Hydroxide? To activate the water glass solution," I will say this DO NOT underestimate the DANGER of molten Sodium hydoxide. ABSOLUTELY do lots of research of safety protocols when dealing with molten sodium hydroxide. https://goo.gl/6xe5Le This was damage done by room temperature sodium hydroxide. Molten would have been much worse. "would you bubble gaseous CO2 through the mixture, or could Dry Ice be used in some way?" If one were making a mold then maybe, but if one is considering sodium silicate as a binder in a glue in a conductive ink then I suspect atmospheric CO2 is sufficient , but you could breath on it to speed it up. Just curious, since I'm not an expert in chemistry.

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  • How to Make a Cheap, Portable Magnetic Stirrer

    "I guess old age has finally kicked into the grey matter. I kinda thought it was the magnets that were the primary factors, Not air movement!!!"you were right the first time. Its all about the magnets and nothing to do with air movement. For clarity, I'll cover the instructable. It is about re-purposing a throwaway old CPU fan into about the cheapest magnetic stirrer that can be found. There is an elongated piece of plastic covering small magnets inside the glass with the solution to be sired, and is spun by the rotating magnetic field from magnets on top of the fan. In the picture with the glass, it is hard to see as anything more than a white blur at the bottom because it is spinning so fast. But, you can easily see the vortex it generated. The actual fan blades serve no p...

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    "I guess old age has finally kicked into the grey matter. I kinda thought it was the magnets that were the primary factors, Not air movement!!!"you were right the first time. Its all about the magnets and nothing to do with air movement. For clarity, I'll cover the instructable. It is about re-purposing a throwaway old CPU fan into about the cheapest magnetic stirrer that can be found. There is an elongated piece of plastic covering small magnets inside the glass with the solution to be sired, and is spun by the rotating magnetic field from magnets on top of the fan. In the picture with the glass, it is hard to see as anything more than a white blur at the bottom because it is spinning so fast. But, you can easily see the vortex it generated. The actual fan blades serve no purpose in the stirring process except maybe to keep the rotor from spinning too fast.Side note: Like an unbalanced tire will cause increasing vibrations when spun faster, slightly unbalanced magnets glued to the rotor can cause excessive vibrations if spun too fast like say after cutting the fan blades off so that it is no longer loaded by air resistance, the magnets on top may cause excessive vibrations if it spins faster and there the magnets are not balanced.

    Not being too critical but try plugging in some reasonable values on air pressure. If the air pressure in ones lab is 1 bar, and given a single stage radial fan can at best only generate a 0.1 bar pressure differential (while radial fans are good for high flow rates, they are terrible creating high pressure differential), then all you will have is a partial vacuum of around 0.9 bar. Consequently, one ends up still having lots of air mas working on the blades as they spin generating lots of turbulence, and the drag approximating some function that is the cube of the rate of rotation.But even if a fan could achieve 0.9 bar pressure differential, rather than .1, then have a reasonable vacuum on the underside, but you still have an average 1 bar pressure above of the blades with each passin...

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    Not being too critical but try plugging in some reasonable values on air pressure. If the air pressure in ones lab is 1 bar, and given a single stage radial fan can at best only generate a 0.1 bar pressure differential (while radial fans are good for high flow rates, they are terrible creating high pressure differential), then all you will have is a partial vacuum of around 0.9 bar. Consequently, one ends up still having lots of air mas working on the blades as they spin generating lots of turbulence, and the drag approximating some function that is the cube of the rate of rotation.But even if a fan could achieve 0.9 bar pressure differential, rather than .1, then have a reasonable vacuum on the underside, but you still have an average 1 bar pressure above of the blades with each passing of a fan blade pushing air up only to have it return after the fan blade has passed. All that movement of air is called turbulence, and is wasted energy that becomes nothing more than heat.Without speed controls, like a potentiometer or implementing PWM, the fan blades may still prove useful in preventing the rotor from spinning too fast where a slight imblance in the magnet's placement would introduce excessive vibration.

    Not being too critical but try plugging in some reasonable values on air pressure. If the air pressure in ones lab is 1 bar, and given a single stage radial fan can at best only generate a 0.1 bar pressure differential (while radial fans are good for high flow rates, they are terrible creating high pressure differential), then all you will have is a partial vacuum of around 0.9 bar. Consequently, one ends up still having lots of air mas working on the blades as they spin generating lots of turbulence, and the drag approximating some function that is the cube of the rate of rotation.But even if a fan could achieve 0.9 bar pressure differential, rather than .1, then you have a reasonable vacuum on the underside, but you still have an average 1 bar pressure above of the fan blades with eac...

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    Not being too critical but try plugging in some reasonable values on air pressure. If the air pressure in ones lab is 1 bar, and given a single stage radial fan can at best only generate a 0.1 bar pressure differential (while radial fans are good for high flow rates, they are terrible creating high pressure differential), then all you will have is a partial vacuum of around 0.9 bar. Consequently, one ends up still having lots of air mas working on the blades as they spin generating lots of turbulence, and the drag approximating some function that is the cube of the rate of rotation.But even if a fan could achieve 0.9 bar pressure differential, rather than .1, then you have a reasonable vacuum on the underside, but you still have an average 1 bar pressure above of the fan blades with each passing of a fan blade pushing air up only to have it return after the fan blade has passed. All that movement of air is called turbulence, and is wasted energy that becomes nothing more than heat.Without speed controls, like a potentiometer or implementing PWM, the fan blades may still prove useful in preventing the rotor from spinning too fast where a slight imblance in the magnet's placement would introduce excessive vibration.

    I guess I was arguing on efficiency of no blades vs having blades when the initial argument was questioning the efficiency of placing the fan on table vs letting air flow through. While sitting on the table top would create lots of turbulence, maybe it is not using anymore energy than if air were allowed to flow through the fan. But there will be less vibration with air flow than if the fan were sitting on the table top; and one might find a way to put air flow can be put to good use. Air flow potential uses:1. Thermal regulating the contents of the container being stirred to room temperature. or2. One can have an inverted fume hood if air flow went down.

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  • How to Make a Cheap, Portable Magnetic Stirrer

    "Can't you just take the fan blade off, and drive the stir-bar from the electromagnets that would have made the fan turn?" I Wish it were so because maybe it would be more efficient; but it probably wont work because: 1. Those electromagnetic fields your referring are designed to project radially, and so do there is not much if any field magnetic field projecting axially upwards to the stir bar relatively far away . 2. These fans depend on a hall sensor to know the position of the magnetic in the rotor so a micro chip can determine which coils to excite. The magnet in the rotor is a multi pole magnet. Assuming the first issue was overcome, if the stir bar has a different magnetic field arrangement than the rotor, then the microchip receiving odd signals from the hall sensor...

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    "Can't you just take the fan blade off, and drive the stir-bar from the electromagnets that would have made the fan turn?" I Wish it were so because maybe it would be more efficient; but it probably wont work because: 1. Those electromagnetic fields your referring are designed to project radially, and so do there is not much if any field magnetic field projecting axially upwards to the stir bar relatively far away . 2. These fans depend on a hall sensor to know the position of the magnetic in the rotor so a micro chip can determine which coils to excite. The magnet in the rotor is a multi pole magnet. Assuming the first issue was overcome, if the stir bar has a different magnetic field arrangement than the rotor, then the microchip receiving odd signals from the hall sensors, may not even properly excite the stator fields.

    Not being overly critical but I think you might be overlooking something. Maybe we might try plugging in some realistic values on air pressure. If the air pressure in ones lab is 1 bar, and given a single stage radial fan can at best only generate a 0.1 bar pressure differential (while radial fans are good for high flow rates, they are terrible creating high pressure differential), then all you will have is a partial vacuum of around 0.9 bar. Consequently, one ends up still having lots of air mas working on the blades as they spin generating lots of turbulence, and the drag approximating some function that is the cube of the rate of rotation.Yes a potentiometer on its own will do a fine job as a speed controller. but a PWM circuit would make it far more efficient.

    hrm. "If there are electrolytes in the water you could induce a flow using emf"I have always seen Magnetohydrodynamics use an emf to generate currents between plates conducted by ions through magnetic field causing a deflection in the ions that pushes the fluid. But, can an alternating magnetic fields induce currents in an electrolyte and those currents induce a reverse magnetic field that opposes the initial change in the magnetic field?I guess probably. Important factors would include but may not be limited to: 1. The rate of change in the magnetic field so either you want really powerful magnets or your magnets have to be moving really fast or both. 2. Resistance to current flow in the electrolyte. or maybe we wont get the the kind of movement we are hoping for. take so...

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    hrm. "If there are electrolytes in the water you could induce a flow using emf"I have always seen Magnetohydrodynamics use an emf to generate currents between plates conducted by ions through magnetic field causing a deflection in the ions that pushes the fluid. But, can an alternating magnetic fields induce currents in an electrolyte and those currents induce a reverse magnetic field that opposes the initial change in the magnetic field?I guess probably. Important factors would include but may not be limited to: 1. The rate of change in the magnetic field so either you want really powerful magnets or your magnets have to be moving really fast or both. 2. Resistance to current flow in the electrolyte. or maybe we wont get the the kind of movement we are hoping for. take sodium chloride for example. In water it becomes (Na+) sodium ions and (Cl-) chloride ions. A moving magnetic field would cause + ions to move in one direction while - ions move in the other, in a plane that is transverse to both the magnetic field and the magnetic field's direction of motion. I am moving beyond my area of expertise but overall wouldn't the two momentums cancel leaving little more than a heating effect?

    I searched for a DIY magnetic stirrer for a similar reasons (Coffee), but in a different way. I use calcium carbonate from powdered egg shells (that I process) to counteract the acids (4.5PH) that contribute to coffee's bitterness. It quickly mellows even burnt tasting coffee. If one likes their coffee hot, consume it right away. I on the other hand, stir it a few times as it cools, and then chill it in the fridge for three days. Day by day It becomes even less bitter as cold water can dissolve more calcium carbonate into it, eventually making it slightly alkaline, in theory something close to 8.25PH .Ohh, I am sure there are many that can not imagine waiting that long, but they have not tasted it. Just saying, give it a try once. That is, taste the difference between coffee and calcium...

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    I searched for a DIY magnetic stirrer for a similar reasons (Coffee), but in a different way. I use calcium carbonate from powdered egg shells (that I process) to counteract the acids (4.5PH) that contribute to coffee's bitterness. It quickly mellows even burnt tasting coffee. If one likes their coffee hot, consume it right away. I on the other hand, stir it a few times as it cools, and then chill it in the fridge for three days. Day by day It becomes even less bitter as cold water can dissolve more calcium carbonate into it, eventually making it slightly alkaline, in theory something close to 8.25PH .Ohh, I am sure there are many that can not imagine waiting that long, but they have not tasted it. Just saying, give it a try once. That is, taste the difference between coffee and calcium carbonate vs without. After that, try it chilled, then try it chilled for three days. I like more coffee than I can process this way so I only do this as a treat once in awhile. My thought is, maybe a magnetic stirrer can keep the calcium carbonate powder suspended, and thus speed up the acid base reactions, so that the coffee more quickly reaches its highest PH. After that, let undissolved powdered egg shells settle out for reuse, decant, and enjoy the coffee.

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  • $1 DIY Conductive Ink and Paint From Fire! (non Toxic, Homemade, Cheap)

    "Did anybody try to make conductive glue" Sodium silicate is made from dissolving glass or better yet silica gel into a hot an aquas mix of sodium hydroxide and mixing in water to get water glass. Then activate it with carbon dioxide to form an adhesive

    Certainly can be very easy. For instance a 1.5V battery with two thick wires and a thin copper wire is all that is needed to ignite paper it. The thick wires conduct current well enough to a thin wire that heats up from a large amount of current flowing though it. Its not a stretch to see 5 or 12 volts applied to two conductive ink terminals with a thin section in between generating heat, and we have not even gotten to the loony toons that would try to put 110v to it to see what happens. Im not saying conductive inks on paper should not be done, just that inconsistent ink conductance or design could lead to a fire.

    charcoal briquettes? Two words, The amount of "charcoal ash" means there is a lot more than just carbon. Some vendors even put in crushed powdered rock for fill. But if you don't mind all that then you would probably want to wash out the potassium hydroxide so that it does not eat your paper.

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  • shomas commented on krmartin3's instructable DC Boost Converter7 months ago
    DC Boost Converter

    I have to correct myself, I was assuming continuous output. Watts is a measure of power, not energy. If one needs to get more power then what is put int, it could be done by storing and releasing power quickly over a shorter time. One way this can be done with pulse width modulation the output into on and off duty cycles. spending different amounts of time in each. Over the course of an hour, a source voltage of 18v and a load that draws 8 amps will source 114 watts for each second of that hour. sourcing 114 watts * (3600 seconds, 60 seconds in a minute * 60 minutes in an hour) = 410,400 watt seconds( watt second is an expression of energy = joules). With an impossible 100% conversion, 410,4000 watt seconds of energy / 250 watts output means you can deliver 250 watts for just 164...

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    I have to correct myself, I was assuming continuous output. Watts is a measure of power, not energy. If one needs to get more power then what is put int, it could be done by storing and releasing power quickly over a shorter time. One way this can be done with pulse width modulation the output into on and off duty cycles. spending different amounts of time in each. Over the course of an hour, a source voltage of 18v and a load that draws 8 amps will source 114 watts for each second of that hour. sourcing 114 watts * (3600 seconds, 60 seconds in a minute * 60 minutes in an hour) = 410,400 watt seconds( watt second is an expression of energy = joules). With an impossible 100% conversion, 410,4000 watt seconds of energy / 250 watts output means you can deliver 250 watts for just 1641.6 seconds. That works out to about 27 minutes and 21.6 seconds. In a world with perfect efficiency using pulse width modulation, one could convert 114 watts to 250 watts with a 45.6% on duty cycle on his output, and a 54.4% off duty cycle.

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  • Build Your Own Flat Panel Solar Thermal Collector

    I would not use this for my house's hot water. But, it may work well as a pool water heater. Your right that these signs dont hold up long, but thats because of the sun's UV rays. Painting it will go a long way to protect it from those UV rays.

    Sins ultraviolet light breaks it down. But paint should do a good job of protecting it.

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  • shomas commented on jwmiller's instructable Aluminum Foil Plate Capacitor8 months ago
    Aluminum Foil Plate Capacitor

    Capacitance is proportionate to the area of the plates facing each other. for a given dielectric and spacing, if you double the area you double the capacitance. But two parallel plates do not make efficient use of the surface area of the plate. because it only uses 1 of two sides to each plate. If you role it into a spiral, plate A is facing plate B on both its top and bottom. Furthermore, when you role it, each sheet of aluminum only needs one cut. as the ends sticking out become your capacitor leads. That gives it a shorter path from lead to each part of the capacitor, and results in a lower ESR value, equivalent series resistance that is due to internal resistance in the capacitor. The spiral picture on the right represents two sheets of aluminum that need an insulator on both t...

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    Capacitance is proportionate to the area of the plates facing each other. for a given dielectric and spacing, if you double the area you double the capacitance. But two parallel plates do not make efficient use of the surface area of the plate. because it only uses 1 of two sides to each plate. If you role it into a spiral, plate A is facing plate B on both its top and bottom. Furthermore, when you role it, each sheet of aluminum only needs one cut. as the ends sticking out become your capacitor leads. That gives it a shorter path from lead to each part of the capacitor, and results in a lower ESR value, equivalent series resistance that is due to internal resistance in the capacitor. The spiral picture on the right represents two sheets of aluminum that need an insulator on both top and bottom as depicted in the picture on the left but rolled up.

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  • Wifi operates at 2.4ghz while in the US, while mobile frequencies are typically between 700 and 900 mhz. Lower frequencies penetrate buildings and foliage better, and because of the longer wavelengths, reflect off your chicken wire mess reflector.

    Wifi operates at 2.4ghz while in the US, while mobile frequencies are typically between 700 and 900 mhz. Lower frequencies penetrate buildings and foliage better, and because of the longer wavelengths, better reflect off your chicken wire mess reflector.

    Wifi operates at 2.4ghz while in the US, mobile frequencies are typically between 700 and 900 mhz. The lower frequencies penetrate building and foliage better.

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  • shomas commented on krmartin3's instructable DC Boost Converter1 year ago
    DC Boost Converter

    Even at 100% efficiency, no one can boost 12v@300 amps (3600 watts) to 18v@300 amps (5500 watts): Laws of physics, as in energy can neither be created or destroyed.

    capacitor inductor capacitor (pi filter) will clean up a lot of noise. The second capacitor needs very low ESR rating for best performance from the filter

    Your issue is two fold. One, by itself the voltage is too low. bump it up with more in series before you boost it. two, the power produced is extremely low and such that drawing even a modest amount of current drops the voltage to unusable levels. You need consider this last point when pairing it with a load, because your not going to pull 5 watts from a device that produces less than a watt.

    Can not get more energy out than is put in. Laws of physics and all. His units were given in volts and amp, but it were possible to build a booster to his specs, then for each second it runs it would create more energy than it consumes.

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