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  1. BobK

    Running 3A component from two 2As?

    In your house, you probably have multiple outlets connected to the same 15A circuit. Plug a microwave oven into one and a toaster into another and operate them at the same time and... a breaker trips. Same thing here. Bob
  2. BobK

    Newb question about voltage dividers

    And nobody answered until now. LOL. Bob
  3. BobK

    Capacitor ESR Testing: do you? Should I? How to?...

    You have not given any reason why you need to measure ESR. There are plenty of cheap component testers, about $15 that will test transistors, diodes, resistors, capacitors and inductors. I have one and I am quite happy with it. Bob
  4. BobK

    voltage dropping

    You can make the LEDs run off 12V by changing the resistor. If only the LEDs are using 5V, this is the way I would go. You lose the same amount of power as you would with a linear regulator, but the power loss is distributed over all the LEDs, so it is more manageable. Bob
  5. BobK

    Trouble with multiple voltage dividers

    The pull up is built in to the module. Unfortunately, that was not the best choice, since we probably want the unit shut down when the MCU is booting, which would have happened with a pull down. Bob
  6. BobK

    Trouble with multiple voltage dividers

    From the datasheet: So, there is a 10K resistor between ~SHDN and Vin. To control it you want to connect it to a GPIO pin, and output low to shut it down, output either high or high impendance to enable it. I have no idea what you are trying to do with the voltage divider, it is redundant, as...
  7. BobK

    Beginner Question...

    It's worse than that. The contacts are only rated at 45mA and USB power is rated at 500mA minimum, with higher allowed for devices that implement the protocol and ask for it. Bob
  8. BobK

    Bridge rectifier melted.

    Sizing a heatsink is a complicated calculation. You have to know: 1. The max operating temp of the diodes 2. The thermal resistance of junction to case 3. The max air temp at which it will operate 4. The thermal resistance from case to heatsink (depends on how it is mounted) Then you can...
  9. BobK

    Need Help regarding 12v DC Motor

    And, by the way, 1 HP is 745W, 12V at 1.5A is 36W. So the motor is nowhere near 3/4 HP. If it were 100% efficient it would be 1/20 HP. Bob
  10. BobK

    voltage dropping

    Dave, Can you give us a clue? Bob
  11. BobK

    Location devices

    The trouble with what Hevans is suggesting is that it would not work if an object intervened. This is why we need to know more about the environment in which it will be used. Bob
  12. BobK

    Lithium ion polymer batteries

    http://lmgtfy.com/?q=Lithium+Polymer+battery+uses Bob
  13. BobK

    Complete electronic virgin!

    Like I said, way complicated. Apparently, even the car manufacturers who have installed such systems have not solved all the problems yet. Bob
  14. BobK

    Automatic Switchover from Car Speakers to Headphones

    The only problem with connecting directly to speaker outputs is that they will be too high a voltage for the headphones. Headphones are typically 32Ω, so 100Ω will reduce the voltage by about a factor of 4. Bob
  15. BobK

    PCB alternatives

    Are the parts through hole? If so, veroboard would be fine for small circuits like this. If they are surface mount, there is no alternative to a PCB. Which tools you use, of course, is a choice. Bob
  16. BobK

    Location devices

    If the distance is in 10s of meters or more, you can use GPS, otherwise there is no really good solution in general. Give us more specifics about the distances involved, and the environment in which they operate. Bob
  17. BobK

    Bidirectional Current Source

    Harald, It is supposed to do that (go into saturation). Look at how the transistor bases are connected. They sense the current from the power supply into or out of the op amp and multiply it, much like the pass transistor used on a 3-terminal regulator. I am not saying that the design is...
  18. BobK

    555 timer specialized polarity switcher

    It is the maximum that is of interest. Bob
  19. BobK

    Bridge rectifier melted.

    I'd look for a short at the output of the rectifier before replacing it. What kind of a heat sink are you using? At 60A a bridge rectifier dropping about 1.4V will dissipate 84 Watts. Bob
  20. BobK

    OneWire Forum

    A visual studio forum should be able to help if if the problem is getting the code to compile. Bob
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