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    Fluorescent lamps in series using electronic control gear?

    I would like to make a lamp using many small T5 fluorescent tubes (maybe 12 or 16). I would like to use a dimmable high frequency electronic control gear (not a starter and ballast). You don't seem to be able to get dimmable control gear for 6 W tubes. I was wondering if I could put four 6 W...
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    Which leg is which for PNP power MOSFET IRF5305PbF?

    I have PNP power MOSFETs called IRF5305PbF. The datasheet doesn't say which leg is which. Should it be obvious?
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    Reverse character LCD polarisation?

    If I buy a cheap character LCD that displays black characters with a yellow/green background, should it be possible to change it to yellow/green characters with a black background by removing the polariser and replacing it with another oriented 90 degrees to the original? Would the old polariser...
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    Making a flashing mains indicator LED

    I previously added a mains indicator LED to a hot glue gun by connecting an LED and resistor directly to the mains connection with a diode across the LED to allow current to pass in the opposite direction when the direction changes. For some devices I'd prefer the LED to flash because I think it...
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    Cheap N-type MOSFET for PWM driving many LEDs with 3.3 V logic?

    I'd like to copy this project to automate some RGB LED strips. It calls for some N-type MOSFETs to turn on and off LEDs in a pulse-width-modulated way. What would be some suitable MOSFETs that can permit at least 1 A? I know I could find something myself but I wouldn't know whether it was some...
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    Modifying 4.5 V (alkaline) lamp to run brighter with 3.6 V (NiMH)

    I have a lamp which takes three D-size batteries. It seems to have been designed to function best with alkaline batteries and is relatively dim (in fact the bright and dim settings both appear the same) using 1.2 V NiMH batteries. I was wondering what circuit I might use to increase the...
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    DMM allows current to pass but measures 0 mA

    I have a UNIT UT61E DMM. I have the probes in the correct sockets and the dial set to mA. When connected to a circuit with about 13 mA passing through it (measured with a different DMM), the reading is 0.000. Perhaps in an unrelated issue, when I move the dial to A and move the probe to the...
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    555 timer for a fan

    I would like to use a 555 timer to power a fan for ~4-5 minutes when a momentary switch is pressed. I read that the motor should have a flyback diode to protect the circuit - does it matter what the specification of the diode is or will anything work? I read that the 555 chip can source 200 mA...
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    Cooling soldering iron quickly after use to reduce oxidation

    In my perennial battle to stop my soldering iron tip from oxidising, after switching it off, I rub it against a block of sal ammoniac and then again on my damp sponge to cool it off. I was wondering whether anyone else is concerned about cooling their soldering iron back down after use (I was...
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    The dark theme isn't very dark

    I appreciate that the dark theme is darker than default but it's not as dark as a typical website dark theme. It could go much darker if the text was made lighter as well. And the text entry box is still white!
  11. S

    Sound cancellation

    This video suggests that sound cancellation is possible with just a microphone, amplifier and surface transducer but doesn't explain how the sound being produced by the speaker/transducer is ensured to be 180° out-of-phase with the sound going through the panels. Is it the spacing between the...
  12. S

    Small low-power light sensor

    I would like to make a very small battery (~100 mAh) powered light that turns on automatically when the light level is low. The device will spend most of it's time in light (i.e. stand-by) so it's important that the sensor consumes low power. The LEDs will probably be one or two red SMDs. I...
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    Uninterruptible power supply ratings: conflict between VA and W?

    My understanding is that P = VI and therefore the power rating of a device in VA should be the same as W but this doesn't seem to be the case for every uninterruptible power supply I look at where the VA rating is much higher than the rating in watts. What's that about? Here's a random example...
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    Could a water flow sensor sense gas flow?

    Could a water flow sensor like this one be expected to detect gas flow also? I don't need an accurate measurement; just whether or not there is gas flowing. If not, why?
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    What is the name of this kind of connector?

    I'd like to buy a three- or four-pin connector like the one in the picture below but I don't know what this kind of connector is called.
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    Is it possible to replace keyboard LEDs with neon indicators and a single inverter?

    I want to modify my keyboard for a retro cyberpunk look and replace my LED (scroll, caps and num lock) indicators with neon indicators. I can power a neon lamp from a low voltage using a laptop CCFL inverter but I was wondering if there's any way I could power three from one inverter. They...
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    Spurious voltage readings for open transistor

    I have a circuit I made for an experiment with four LEDs in series behind a transistor with a floating base so the circuit is open and LEDs are unlit. When I measured the voltage across the LEDs I got a stable value of about 2.4 V but when I measure the voltage across the collector and emittter...
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    Adding keys to an old PS/2 keyboard?

    I have an AST KB-102 keyboard but it doesn't have Windows or context menu keys. Is it possible that I could add a couple of switches to the surface of the board and then wire them up into the matrix so they will give useful scancodes to the operating system?
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    Connecting two batteries to one phone through the case

    My Samsung Galaxy S5 is a little old and I would really like to augment the aging battery by connecting my old battery in parallel with my even older battery. I could just buy another new battery but that will only get me a relatively small improvement and this solution uses what I have already...
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    Making a floodlight from the CCFLs from many broken monitors - need >1.2A, 700-1000V inverter

    I want to build a floodlight by combining the CCFLs of many broken LCD monitors (laptop and desktop) The laptops come with nice, compact inverters which I can re-use relatively easily but the desktop screens use massive circuit boards with a load of unrelated stuff which I think is too bulky...
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