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  1. C

    74HC138N: IC Beginnings Chapter Two

    Imagine you have some of these 74138's on a bus we will call the "enable" and the bus contains 3 lines. How many 74138 can you separately activate with 3 lines? Once you have "enabled" this particular 74138, you have another 3-line bus called "select" bus and this allows you to select 7...
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    Looking for basic circuits on RGB LEDs

    Use 3 pots and 3 transistors then go to PWM:
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    looking for circuit designer for a youth project

    1. a flickering LED candle. talkingelectronics.com\projects\ArcWelder\ArcWelder.html talkingelectronics.com\projects\PIC Fx\PIC_FX-1.html 2. a colour changing LED light colour change LED $1.50 3. A mini traffic light
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    LED Chaser Help

    5 LED Chaser
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    looking for circuit designer for a youth project

    Look on Talking Electronics.com website for LED and transistor projects
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    Deciphering datasheet for PCB footprint

    The leads are rectangular. I think you mean: "PADS." They can also be: "Rounded Rectangular" - depending on how professional you want the board to be. The most common surface mount components are 1206 (3216 metric): 3.2 mm × 1.6 mm (0.126 in × 0.063 in). This size can be hand-soldered...
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    Is it possible to limit current with constant voltage?

    That is not the current taken by pi. It is recommended that my car be stored in a garage 15 metres x 30 metres. See what I mean? ????
  8. C

    Problem with Power Transistor MJ10012

    The Darlington transistor has a very low value resistor inside between the base and emitter (1k) . The Halogen lamp needs 6 x 150watt to turn it ON. This is 900watt = 3.75 amps. The gain of the transistor is about 300 so the base current needs to be about 13mA. To get 13mA into 1k requires...
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    Discharge path for buck-boost converter

    I don't know what you want. The diode is around the wrong way.
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    this close to setting the perfboard on fire, 2013 darlington array

    You need a resistor in series with each LED.
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    Deciphering datasheet for PCB footprint

    Keep everything "imperial" - "inches" there are one thousand "thou" in one inch. All my PCB's are in inches as most components are measured in inches. You can make the pads circular or oval and any pad can be made smaller than the rest so tracks can be passed between the pins. Two hundreds...
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    Is it possible to limit current with constant voltage?

    How much does the pi take?
  13. C

    Swapping batteries for Fish Finder

    How long do you want the fish finder to operate for?
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    Looking for a small, low rpm, higher torque motor. Help please?

    PWM is no different to a pot. You need my Motor Speed controller if you want to reduce the RPM of a motor at a varying load. But the best solution is a gearbox and 5 pole motor, or a stepper motor. The 30rpm motor you saw has an inline gearbox (cyclic / sun/planet) or compound gearbox.
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    Pic sine wave inverter H-bridge

    Using push-pull makes more use of the transformer and you effectively get twice the output wattage. But for this it's best and cheapest to use a centre-tapped transformer. The choice of transistor or MOSFET depends on the wattage. For 50 watt I wouldn't bother to go MOSFET.
  16. C

    How to power an LED, NEED CLARITY.

    The illuminator MAY have an internal regulator as the specifications say 14.4v to 16.2v @ 300mA and 16v is within this range. You may not need a dropper resistor AT ALL.
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    need help going green and willing to pay for help! solar / relay / timer control

    You are talking about peak generating, I am talking about detecting a cloud. Two entirely different things.
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    need help going green and willing to pay for help! solar / relay / timer control

    A cloud is a cloud is a cloud.
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    need help going green and willing to pay for help! solar / relay / timer control

    The simplest idea is to use a smaller solar panel to detect the condition of the sun and use the output to switch the A/C on and off. This way you don't have to touch the output of the main PV set-up. All this can be done with a solar panel, battery, a chip and relay.
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    Newbie

    Look here: http://www.talkingelectronics.com/projects/BasicElectronics-1A/BasicElectronics-1A_Page1.html
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