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  1. BobK

    Voltage regulator for LED panel

    It's not really too bad. You waste about 1/3 of the power driving them that way. Dimming, however, should be done by PWM, not by varying the voltage. Much more efficient since it keeps the LEDs off a percentage of the time. Bob
  2. BobK

    Voltage regulator for LED panel

    It is possible but wasteful. The most efficient way to do it is run as many as possible in series, then drive each series string from a switch mode constant current supply. Did you look at the resource I linked? Bob
  3. BobK

    Voltage regulator for LED panel

    Driving 100 LEDs in parallel with a voltage source is a real no-no. Please read this resource on driving LEDs. https://www.electronicspoint.com/resources/got-a-question-about-driving-leds.5/ Bob
  4. BobK

    Converting int to string - C Programming

    The itoa() function should be in the library. No need to include the source. Bob
  5. BobK

    Convert +12V DC to -30V DC

    If the negative supply is at -30V the positive supply can be no higher than 0V. So why not just supply it with 0 and 30V? Bob
  6. BobK

    How calculator Work

    By using a computer chip. multiply up to 3 times shift Bob
  7. BobK

    Help with powering immersion heater!!!

    If this is an immersion heater, and you connected power without the element immersed in water, you probably burned it out. Bob
  8. BobK

    Determine the Vcbo of a germanium transistor and the voltage drop along the connected components.

    I believe they are made out of flower petals: Whoops, that is Geranium. Never mind. Bob
  9. BobK

    Relay to switch a relay?

    Yes. You can switch a bigger relay with the on board relay. Bob
  10. BobK

    RC charging and discharging

    The circuit can be reduced to a capacitor charged through a single resistor from some voltage. These two quantities have been give by other posters, but not how they were calculated. If you want to know how to solve this, look up Thevenin equivalent circuits. Bob
  11. BobK

    H Bridge Circuit

    To get max speed and torque out of a stepper you must vary the voltage with the speed. This is to compensate for the fact that the load is an inductor, and will not get to max current immediately, but it will take a delay inversely proportional to the voltage. That said, if you don't need to...
  12. BobK

    Piezo as a contact microphone

    And I am saying that a clue that a particular piezo is good as a contact microphone, is that is is sold as a contact microphone. Bob
  13. BobK

    Very compact voltage dropdown

    Correct, the 9V would last the least long of those 3 options. I only suggested the CR123A because you specifically said 1 battery (cell actually.) If I were building it, I would use 2xAA or even C for longer life. Bob
  14. BobK

    LM338 power supply problem

    Sounds like your 10K pot does not go down to zero. Try shorting it out and see if you get 1.2V. Bob
  15. BobK

    general pull down/pull up microcontroller input/output questions

    But why go to all this trouble when there is switched power available? Bob
  16. BobK

    I need assistance on one way transmit

    Regarding 433MHz modules. If he lives in the US these are not legal. Okay in Europe. 1.2GHz modules are okay in the US. Bob
  17. BobK

    One on-off switch for 2 circuits ?!

    Easiest way is to use a DPST switch rated for 220V and the current needed for the high voltage lamp. Your circuit will put 220V acroos LED when the switch is off. Also, the LED needs a resistor for current limiting. Bob
  18. BobK

    general pull down/pull up microcontroller input/output questions

    I calculate that the 0.75mA will run down your car battery in just 266,666 hours, so I see your problem. Seriously, though. Draw the power from one of the lines that is turned on only when the ignition is on. Problem solved. Bob
  19. BobK

    Piezo as a contact microphone

    Yes, they are the same thing. But one is optimized for putting out sound, and the other for picking it up. A dynamic microphone and a 12 in woofer are also the same thing, but I would not use the 12 in woofer to record my voice nor the dynamic microphone to blast the car next to mine with...
  20. BobK

    Instructions needed for 3D light squared kit

    If it is a kit, it surely must have come with some instructions, no? Bob
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