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  1. BobK

    increasing voltage or current

    You can look at the resource on using a transistor as a switch. https://www.electronicspoint.com/resources/using-a-bipolar-transistor-to-turn-a-load-on-and-off.30/ Bob
  2. BobK

    increasing voltage or current

    There are two issues here. First is how to connect 6 LEDs efficiently. This is done with series and parallel as Gryd3 suggested. There there is the issue of driving them from the board. Let's assume you end up with two strings of 3 LEDs to put in parallel with each for each of the 10...
  3. BobK

    Convert uneven pulses

    No, we are saying count the opens instead of the closes. Then all the pulses will come at the same interval, with the first one coming when you release the dial. Bob
  4. BobK

    How to design analog circuit

    dv means delta v, change in v over time. That equation says that if there is a current I into (or out of) the capacitor with capacitance C, the the change in voltage over time will be C dt. For example, a 1F capacitor charging at a rate of 1A will rise by 1V each second. Do you know any...
  5. BobK

    Reducing amps in a circuit without change in the voltage

    Yes, and I noticed the answer to your question that was given in that thread. The negative of the supply is grounded. There is no "AC leakage" to worry about. Since the negative is grounded, a small DC current can go from the positive, through the LED, through you body to ground. No mystery...
  6. BobK

    Convert uneven pulses

    I second what Minder says. Simply count the falling edges. Bob
  7. BobK

    Can a button open a circuit?

    Another possibility, with a small amount of electronics, is to have the music stop when any USB drive is inserted, then resume automatically after some time period. Bob
  8. BobK

    Reducing amps in a circuit without change in the voltage

    He is guessing that the power supply uses a line (60Hz) transformer, followed by a swiitching DC - DC regulator. Bob
  9. BobK

    What is Duo Decimal application.

    It is a microcontroller with an interpreter on it. Much like a basic stamp. It is minimalist in that there is only one button and a 1 digit display, but it is still a self-contained programmable device. It has nothing to do with base 12. It is an academic excercise, not very useful. Bob
  10. BobK

    Choosing connection scheme for high power LED application

    Here is a link to a power supply that could drive all 4 in series. http://www.trcelectronics.com/View/Mean-Well/HLG-120H-54.shtml Bob
  11. BobK

    Reducing amps in a circuit without change in the voltage

    True enough, but that kind of supply is pretty much a thing of the past. Most are now switch mode and regulated. Bob
  12. BobK

    Feedback loop for constant voltage amplifier. Simulated Aircraft Power.

    Wait a minute. You have a 200W amplifier and it's voltage output drops when supplying 200mA? Something is wrong here. 117V at 200mA is only 23W. The amplifier should be able to handle this easily. Edit: Okay, I see that there is a transformer in the output. I suspect the transformer is the...
  13. BobK

    Formulas for Voltage, Current and Resistors

    You probably just blew the fuse. There is a fuse in current measuring path. Usually there are 2, one for the Amp range and another for the lower ranges. Bob
  14. BobK

    Timer with NE555

    A washing machine cycles through several states controlling valves (for water intake) and a motor, with both wash (slow, alternating directions) and spin (fast, single direction). You cannot control all this sequencing with a 555 timer. A much more complex circuit and probably at least 3...
  15. BobK

    Multiple LED's on circuit

    If you have 3V LEDs and a 9V battery, the best you can do is 3 strings of 2 LEDs in series. You would need a resistor in each of the 3 strings. What currernt are the LEDs rated for at 3V? You would use this to calculate the value of the resistor from Ohms law. You need the resistor to...
  16. BobK

    Reducing amps in a circuit without change in the voltage

    No you don't. If the circuit requires less than 1A at 12V that is what it will draw. The Amp ratting of a power supply is the max that it can deliver. That is why you can plug a 100W light bulb (about 1A) into the same socket as you can plug a 1500W heater (about 13A) into the same socket in...
  17. BobK

    Testing Transistors With Digital and Analogue Multimeters.

    What settings are you using on the multimeters? If using a diode check setting, it should be + to P - to N, but if using a resistance setting, the opposite. Bob
  18. BobK

    Need to replace DC gearmotor with a stepper one

    Do you realize that gearing a motor down increases the torque by the same ratio as it decreases the RPM? If you used say, 10:1 gearing on your stepper you would only need 3 in pounds instead of 30. Bob
  19. BobK

    Voltage regulator for LED panel

    If the frame rate is 120 fps, a 15000Hz PWM will flash 125 times during each frame. You will not see any flicker affect. Bob
  20. BobK

    Voltage regulator for LED panel

    Not if the frequency is high enough. It will flash many times during a single frame, which will not be visible at all in the video. And it is the easiest way to get something like linear dimming. You would have to change the voltage in a non-linear way to achieve the same. Bob
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