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  1. BobK

    LEDs in series?

    You have the LEDs wired in parallel with no resistors. This is not the way to do it. As you have discovered, they do not share the current equally. There are minor variations between all the LEDs which causing the unequal sharing. You lucked out in that your power supply was a current source...
  2. BobK

    fried L298N, stepper motor fun...

    Build your own bridge using MOSFETs, they will have much less loss and need less (possibly no) heat sinking than darlington transistors. Bob
  3. BobK

    Calculating frequency

    Did you use the right multipliers? 1/1000 for mH and 1/1,000,000,000,000 for pF? I get the answer in the example. Bob
  4. BobK

    LEDs in series?

    If the LEDs are in series, then they all get the same current. If they are the same model of LED their brightness should be close enough to not be distinguishable by eye. Show us a circuit diagram. Your explanation sounds more like they are in parallel. Bob
  5. BobK

    L293D voltage

    Well, if you cannot fit a stepper there, and you don't like my other two suggestions, I will give you a third one. Take out the motor and connect a stepper through a flexible shaft. Bob
  6. BobK

    Please let me know your idea about this circuit

    I think the problem is that these transistors do not respond fast enough for 10nS pulses. Set it to 10uS and see if it improves. Bob
  7. BobK

    L293D voltage

    The only way you can make a DC motor position something accurately is by using feedback. The simple way to do this is to have the part it is moving move a potentiometer geared such that the range of motion of the platform corresponds to the range of the pot. Then you use the pot as a voltage...
  8. BobK

    Hearing Aid Design

    Does you hearing aid have a wireless interface? If not, you are out of luck. The principle is simple. The hearing aid has a wireless receiver that can accept audio from the little box that is the transmitter. Various audio sources can be connected to the transmitter box. My father-in-law...
  9. BobK

    L293D voltage

    That will work about as well as using a hammer as a screwdriver. Bob
  10. BobK

    Infrared emitters and receivers

    That type of receiver responds only to IR pulsed at a specific frequency. In this case, 38KHz, which is a very common one. Connect 5V to pin 3, and ground pin 2. Pin 1 is the output. It will be high when no IR at 38KHz is detected, and low when it is. Rig up a '555 to flash you emitter at...
  11. BobK

    5-10 watt led circuit needed.

    I believe that direct connection of LEDs to mains is not allowed to be discussed on this site. Bob
  12. BobK

    Combining notebook (laptop) chargers for more POWER ?

    You put a resistor in series with each power supply's + line, connecting the other sided of the together to go to the laptop. Bob
  13. BobK

    grounding in electronic circuits

    The other place an actual earth ground is important is in radio transmitters and sensitive receivers. When used with a monopole antenna, the earth ground is the other terminal. Bob
  14. BobK

    I want to build an electronic device but need help

    There are no transistors in that diagram. There is a chip and some other components. When you say "like the light on a cell phone camera", do you mean that bright? These are very bright and use a lot of power. They probably cannot be run from a button battery. Bob
  15. BobK

    2ch remote with l298n and nema 17 connection

    You can connect both the limit switches in series with either of the power leads or the motor leads using the NC contacts. That way, if neither limit switch is activated the motor runs and if either is activated it does not. Bob
  16. BobK

    Combining notebook (laptop) chargers for more POWER ?

    Yes, the one with the higher voltage would supply all the current. 19V 60W gives me all the info I need. That comes out to 3.15A. I would use resistors that drop 250mV. Which works out to 0.08 Ohm resistor. They would need to be 1W resistors, though I would go 2W for extra safety. You...
  17. BobK

    5-10 watt led circuit needed.

    I guess I was unclear, that is exactly what I was suggesting. Bob
  18. BobK

    How to control 700 solenoids?

    The WS2811 solutions sounds good at first, but if you think about it, what you have is 1 chip per 3 solenoids, whereas a latched shift register (74x595) will require 1 chip per 8 solenoids, and the interface is actually simpler, requiring 3 lines instead of 1, but no timing constraints. You...
  19. BobK

    5-10 watt led circuit needed.

    Use one of the 7W 120V bulbs used in night lights, and in the old days as Xmas tree lights. Bob
  20. BobK

    Combining notebook (laptop) chargers for more POWER ?

    Diodes are the wrong way to combine two supplies that you want to share equally. You need to use resistors instead. I would check the output of the two chargers, determine how much voltage difference there is at full load, then use resistors that would compensate for this difference i.e. drop...
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