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  • DiegoZ1 commented on DIY KING 00's instructable DIY Bladeless Fan From Scratch2 months ago
    DIY Bladeless Fan From Scratch

    Good idea, just keep in mind that unless you put the heat generated by the peltier elements OUT of the room or better, the house, the net cooling effect wil be negative, would be like putting a window air conditioner inside a room.

    Hey sue.donim.144, you have an inquisitive mind! First, the thing is to deliver variable energy by varying the RMS (like averageing the voltage for DC) voltage, that's what you get by "chopping" the voltage with the 555 timer square signal, so in terms of energy DELIVERED, is equivalent to a pot, but the difference is in how the variable voltage is delivered. With a pot, energy is divided between the motor and the pot's resistance, so you're wasting energý by having a passive element in the circuit, since current flows by the resistance, it dissipate energý as heat (Wattage=Current Squared times Resistance), so for a 40 watt motor, dividing the voltage in half with a resistance generates 20 watts of heat. When you deliver a pulsed voltage to the motor, you deliv...

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    Hey sue.donim.144, you have an inquisitive mind! First, the thing is to deliver variable energy by varying the RMS (like averageing the voltage for DC) voltage, that's what you get by "chopping" the voltage with the 555 timer square signal, so in terms of energy DELIVERED, is equivalent to a pot, but the difference is in how the variable voltage is delivered. With a pot, energy is divided between the motor and the pot's resistance, so you're wasting energý by having a passive element in the circuit, since current flows by the resistance, it dissipate energý as heat (Wattage=Current Squared times Resistance), so for a 40 watt motor, dividing the voltage in half with a resistance generates 20 watts of heat. When you deliver a pulsed voltage to the motor, you deliver less RMS voltage (from zero frequency = direct current up to the response limit of the motor) What's this response limit? Well, the motor, either brush or brushless has to magnetize its core and armature to generate torque, which moves the motor. If the frequency of the signal is too high, you may not get time enough to do so, or the torque generated will be too low to turn the motor. Since the transistor is turning ONLY ON and OFF (square signal driving it), the ON resistance is way low, so the energy dissipated is low (Current Squared times Resistance), and the OFF state is practicaly infinite resistance (zero dissipation); there are also transient usages of energy, but for this simple solution this explanation holds true. And there's also a more complex way of controlling a motor by varying frequency, pulse width and amplitude. As for turning the motor on and off, off course you're putting more mechanical and electrical stress on the motor, but the net effect does not represent serious damage. As for the fan's motor, it is designed to work always on for a long time; they usually fail because the lubricant of the axis dries up and/or gets contaminated with friction caused dirt.

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  • DiegoZ1 commented on fungus amungus's instructable Open a Stuck Jar with a Knife1 year ago
    Open a Stuck Jar with a Knife

    You're absolutely right! Hitting the lid with the knife can crack or dent the glass border, so pieces of glass can enter the food... Breaking the seal or loosen the lid from dried food is easily accomplished the way you explained. As an added bonus, the same method (knife between lid and glass) works for oppening beer or soda bottles without the risk of breaking something.

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  • Homemade wood mini lathe with hand Drill

    Very neat! No soldering... Ideal for ocassional work! Is there a way to buy these pieces already made, like a kit?

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