Recent content by CWatters

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    Resists for etching Aluminium with NaOH

    Thanks Scott, great suggestion.
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    Resists for etching Aluminium with NaOH

    I'm trying to find a cheap DIY method to etch holes of various shapes through 0.3mm Aluminium sheet using 5-10% Sodium Hydroxide. The idea is to apply a resist to the Aluminium then selectively ablate it off using a diode laser cutter and then dissolve away the Aluminium using Sodium Hydroxide...
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    Charging and discharging a battery at the same time

    Is it me or... I was surprised to discover quite a few people think it's possible to charge and discharge a battery at exactly the same time. For example laptop users think the battery is simultaneously being charged by a charger and discharged by the processor at the same time. In reality the...
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    Calculating Force for Garden Storage Box Lid: A Newton/Kilogram Question

    I don't think Cos(psi) is necessarily a real angle you can point to on the drawing. I might be wrong but I think he introduced Cos(psi) just to simplify the equation for h. He defined Cos(psi) right below so you could substitute and eliminate Cos(psi) from the equation for h to produce a new...
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    Does anyone know how this motor from Quantum Energy works?

    Does anyone know how this motor from Quantum Energy (aka Inductance Energy) works? They have a series of videos on their channel, this being is just the latest. I think their facory in Byron, Wyoming was part funded by a government loan.. Factory and training/recruitment center..
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    Force required to strip threads

    Thanks for the replies. Yes I said bolt but the actual situation was a threaded stud. I hadn't thought the difference mattered but can see it could.
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    Force required to strip threads

    Not homework and I'm not a Mech Eng. I was trying to follow a discussion elsewhere about a building foundation that involved 2.75" diameter steel bolts. Two nuts are locked together on the bolt and embedded in concrete. Threads of the bolt itself are sleeved so only the nuts are anchored into...
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    I don't understand force as a function of time

    a = (6t^2)/5 Mass is 2.7kg not 5kg? Or is your problem slightly different?
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    Is Orbital Solar Feasible for the Future?

    Do we really want to collect more energy from the sun and inject it under the blanket of our atmosphere? Should we be trying to do the reverse? Set up transmitters to beam energy into space to get rid of it and cool the planet? I'm only half serious.
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    Is it possible to reduce back EMF in DC motors using shorting rings?

    Not sure what's behind the original question but some people think that reducing or eliminating back emf is the key to making a motor more efficient (possibly more than 100% efficient but obviously that's not possible). This is wrong. Some modern DC Brushless motors are incredibly efficient, as...
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    Key fob only works on battery and not power supply. What?

    When you remove the battery does the +ve battery terminal short the power supply by contacting the -ve terminal on the pcb? Especially if you have it the other way up to press the buttons. Try replacing the battery with cardboard when on the power supply.
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    B Measuring change in g with height (TV program many years ago)

    Bit of a long shot but can anyone remember a TV program where the presenter measured the weight of something at ground level and compared it to the weight at the top of a tall building, possibly the Empire State building? Sorry I can't recall more details. Think it was at least 10 years ago...
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    Virtual displacement for a block sliding down a wedge

    Imagine what happens if the small block is constrained to move vertically downwards. The wedge would be squeezed and pushed to the left. Similar to squeezing a slippery melon seed between fingers.
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    Graph of waveform across diode shown by CRO

    +1 I would treat the diode as a switch. Forward Bias = Switch is conducting => the output is connected to 0V Reverse Bias = Switch is open => the output is just connected to the input via the resistor.
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    Other Becoming an Engineer: Considerations and Personal Experiences

    Here in the UK we have an Open University which mostly runs courses for people in employment by post/internet. Some years ago my wife did a management course while she was in full time employment. It was quite a lot of work but not impossible. If your employer is offering to pay you to do a...
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