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  1. BobK

    Button to button circuit

    Yes, use an SPDT momentary switch for the horn, and an SPST toggle switch for the light. If you have the light switch off, the horn will operate normally. If you have the light switch on, pressing the horn button will turn off the light while pressed. Bob
  2. BobK

    Car battery jumpstart gadgets

    That must be a pretty low current charger. I have a 10A, which is still pretty low, and it has always charged enough in about 30 min to start the car once, then I drive around to charge it some more. Or maybe my battery has never gotten as low as yours does. Bob
  3. BobK

    What charger to use for LI-ion batteries

    Or, at least we can hope so. Bob
  4. BobK

    Sick of my breadboard! quality breadboard recommendations please.

    Breadboards have too much stray capacitance for RF work. Use stripboard, and keep everything compact. Bob
  5. BobK

    Capacitor between collector and emitter help

    It may not be a good circuit, your point about running current through the earphones is well taken, but I suspect it will work. It is basically just a crystal radio with the transistor serving both as a detector and amplifier. Bob
  6. BobK

    Using a REED SWITCH with uC Question

    Before worrying about the current drawn, you need a circuit that works. With the circuit you show, the input is floating when the the switch is open. If the micro has pulldown you can enable, and you enable them, the circuit would work, otherwise, it needs a pulldown resistor (from the GPIO...
  7. BobK

    Car battery jumpstart gadgets

    Huh? I have been using mains to jumpstart my cars with dead batteries all my life.. Yes, it take 30 min or so to charge the battery, but that just meant 30 minutes that I didn't have to be at work :p Why are you in such a hurry? Bob
  8. BobK

    Difference in output states

    Push pull outputs will connect the output either to the V+ supply or to ground. They do not need a pullup resistor. Open drain outputs can only connect the output to ground. They need a pullup resistor to produce a high output. Open drain outputs can be wired together to implement OR logic...
  9. BobK

    Use AC speakers in Car

    I never thought about this before, but, the capacitor in the output of a single supply AC amp is basically the same thing as a switched capacitor negative voltage generator. One end of it is tied to ground (through the speaker), while the other end alternates between V+ and ground with the...
  10. BobK

    Car battery jumpstart gadgets

    Very cool. I bet you could also charge it from some D cells, just in case the battery was too far gone. Bob
  11. BobK

    Car battery jumpstart gadgets

    You can jump start a car (with a depleted battery,) using 8 AA alkaline cells. But only by charging the car battery for an hour or two. The batteries have enough energy to start the car, but not enough power. A home AC outlet has enough power to jump start the car, but at the wrong voltage...
  12. BobK

    Calculating frequencies

    If you simply ignore the exponents, the result will be in Megahertz. Bob
  13. BobK

    AdaFruit NeoPixel Ring - Chinese alternative ?

    If they are using WS2812 LEDs, they will be compatilbe as long as you match up the 3 connections correctly. Bob
  14. BobK

    1W audio power amplifier driven by electret ?

    Look fot a horn type speaker to get the volume yoi need at 1 W. Have ypu ever seen a bullhorn? Very compact, very loud. Bob
  15. BobK

    Wiring LEDs to Corresponding Switches?

    The LED lights you linked are intended for direct connection to an auto electric system, which runs 12-14V. Adding a 560 Ohm resistor would likely make them very dim. The switches you linked appear to be a mixed bag. Bob
  16. BobK

    Wiring LEDs to Corresponding Switches?

    The LEDs in the switches may require a resistor. Some would have one built in, others won't. You 12V LEDs have the resistor built in, so they are okay. Bob
  17. BobK

    Op amp problem

    So at 1V the output should be -10V. How do expect to get that when the power is a single ended 15V? You need dual supplies to get negative voltages out. Bob
  18. BobK

    To build step counter app using using android studio

    I think you would have better luck on an Android programming forum. Bob
  19. BobK

    Servo motor control with POT

    If you insist on doing it with a program loop, you would turn both pins on, then, loop until the lower time is reached, turn it off, continue loop until the higher one is reached, turn it off. Bob
  20. BobK

    Resistance of wire seems to go down when part of a circuit?

    For ten feet of wire to have a resistance of 2 Ohms it would have to be 33 AWG. Bob
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