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  1. BobK

    Transistor switch circuit base issue

    You need a pull down resistor from the base to ground to insure that the transistor is off when there is no signal at the base. Something like 10K to 100K should work. Bob
  2. BobK

    BC 547 NPN Transitor Vb, Vee & Beta value?

    Um, you cannot replace a P channel MOSFET with an NPN transistor, you would need a PNP transistor, unless you are making changes to the surrounding circuitry. How about showing us a schematic of using the MOSFET. Bob
  3. BobK

    uA741 op amp has 85K of resistance?

    The Quiescent current spec tells how much current is used by the op amp when no current is sourced or sunk from the output. To use two 9V for a dual supply, hook the + of one to the - of the other. This connection is then ground. The other + is V+ and the other - is V-. Bob
  4. BobK

    Series RC circuit for LED

    Jibby, You should read the entire thread before responding. The issue was already resolved. Bob
  5. BobK

    need help with choosing the right encoder/decoder

    In other words, you are asking us to go read the datasheet for you. Bob
  6. BobK

    Halloween Project Help!

    +1 to Fish If you had to do it withoug a micro, you could run several oscillators at different (unsynchronized) freqencies and AND the outputs together. Bob
  7. BobK

    Voltage or Amplitude?

    Yes, that amplifier is clipping. You need to reduce the gain. Bob
  8. BobK

    Help on circuit

    No, the uController IS the PWM controller. Bob
  9. BobK

    Wireless reed switch

    No, that is too simple Harald. The reed switch operates a solenoid. The solenoid releases a 1 inch ball bearing that runs down a spiral track. It Then falls into a cup at the end of a 1 m long lever The lever, through gearing runs a fan. The fan provides wind to move a model sailboat...
  10. BobK

    Wireless trigger for LEDs and buzzers

    You can get a free C compiler from Microchiop which is not limited except in optimization. Why not use it? Bob
  11. BobK

    Reverse voltage on DC/DC

    It would be safer to cut one of the traces from the DC / DC, isoltating it from the supplied voltage. Bob
  12. BobK

    Series RC circuit for LED

    So the diagram was not ambiguous after all -- there was no circuit. Bob
  13. BobK

    Series RC circuit for LED

    Since the diagram does not show a circuit, I guess it is ambiguous. He should have seen a flash though, at least once!. Bob
  14. BobK

    Series RC circuit for LED

    Gonzo, He has a resistor. Bob
  15. BobK

    Series RC circuit for LED

    Have you tried lighting the LED directly from the battery to make sure it is working? Are you sure you have the correct polarity? I tried this and I get quite a flash, diminishing over about 2 seconds. Bob
  16. BobK

    (woo woo) transformers 1:5 ratio - were to buy

    You've been scammed. Stop now, while you still have any money left. Bob
  17. BobK

    Electronic Countdown Timer Circuit

    You really have gotten off to a bad start here. Do not start multiple threads on the same topic. https://www.electronicspoint.com/electronic-countdown-timer-circuit-t263383.html Bob
  18. BobK

    Constant Battery charger

    Transistors do not amplify current in the way you are using the term. They control a current with a smaller current. The source of all current is the battery. You cannot take current out of a battery, store the energy, and then put it all back into the battery, there are always losses. I...
  19. BobK

    Help with a two-way circuit?

    Do you already have a circuit to make the LEDs sync with the bass output? Bob
  20. BobK

    Driving Peltier Device through L298N to control Temperature

    Sure, but people control the "brightness" of LEDs using PWM as well, which is the same thing. Bob
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