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  1. BobK

    The control circuit in the engine speed and reverse

    How many YouTube hits can I get? Bob
  2. BobK

    Confused by electricity!!

    It is you who is looking at it backwards. The voltage from D to A has to be 12V because the battery is connected to these two points, and the battery is a voltage source, i.e. the two terminals always have 12V between them. The current (not voltage, voltage does not flow) flowing through...
  3. BobK

    Hobby builder

    Depends on your switching frequency. You need enough amps to make the switching time a low percentage of the PWM period because the MOSFETS will dissapate a lot of power which switching. The total gate charge of the MOSFET tells you how much charge you source / sink to turn them on / off...
  4. BobK

    Boeing Lithium Battery Problem

    New article with a lot more info: http://www.nytimes.com/2013/01/30/business/boeing-aware-of-battery-ills-before-the-fires.html?hp The failures were not that uncommon: And appear to be caused by sudden over-discharge: But that makes little sense, where did all that power go...
  5. BobK

    Boeing Lithium Battery Problem

    My guess of software problem is looking better. Bob
  6. BobK

    Connecting a power supply to battery

    If the battery operated part has no other ground, just connect it to the ground of the power supply. Bob
  7. BobK

    Relaxation oscillator Noob need education

    I have come across people promoting solenoid engines before. Don't remeber if it was this forum or another. Bob
  8. BobK

    Relaxation oscillator Noob need education

    Please, don't take my black helipcopter, please! I'll be good. Bob
  9. BobK

    Trouble with PIC and Relay controlled model train point motors

    Yep, it is probably the cause of your problem. When you remove voltage from a coil it tries to keep the current flowing and the voltage can rise to a very high level before it can find a way for the current to flow. You need to place a diode wired in reverse (i.e. cathode to the positive...
  10. BobK

    Electronic Message Display Board Using Bluetooth

    To summarize what daGenie said: this is not a beginner project. Bob
  11. BobK

    Boeing Lithium Battery Problem

    I'm still betting on a software glitch, but then that is because I am a software engineer. Edit: Software is really good at producing irreproducible errors that rarely occur. Bob
  12. BobK

    Trouble with PIC and Relay controlled model train point motors

    Do you have a flyback diode across the relay coil? Bob
  13. BobK

    Light house flasher

    You can get SSRs that have zero cross output, which would allow you to make an isolated dimming circuit. The circuit would simply have a variable delay after zero cross goes high before switching it on every half cycle. Bob
  14. BobK

    how to signal an alarm at point

    And as long as you only need 10m accuracy. Bob
  15. BobK

    Help with an R2-D2 LED Circuit

    Adding a third stage to a bistable mutivibrator does not make it a tristable multivibrator. I tried this in simulation, just to see what would happen. With 2n2222 transistors, 1K collector resistor and 50K / 0.1uF timing compoents, I got a bistable to work as expected. When I add at third...
  16. BobK

    Relaxation oscillator Noob need education

    But you don't understand, all you have to do is make the one that is pushing power the one one that is pulling, then reverse it on the next half-cycle, and it runs forever with no power source! Bob
  17. BobK

    High amperage DC-DC down conversion

    Might be, but not enough amps for your application. I hope some knowlegeable people will comment on my suggestion, which is likely to be the least exensive way to do it. Bob
  18. BobK

    High amperage DC-DC down conversion

    I also am not well versed in high current, so take this with a grain of salt, and I hope others will comment. A buck converter is basically a PWM signal applied through an inductor. Your starter motor is an inductor, so all you need is the PWM. If you could use a PWM signal with 1/4 duty...
  19. BobK

    SPDT Switch using N-JFETs

    What is wrong with analog switch IC's? Bob
  20. BobK

    12 volt voltage "clamp?"

    Or, you could try changing the resistors. Measure the current at 12V multiply to get the current and voltage drop the way it is specified, then recalculate for 13.5V. Bob
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