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  1. BobK

    Does electron die?

    Where were you when I was arguing exactly this point, and others insisted that Ohms law applies to every component including diodes, transistors, inductors and capacitors, and even "negative resistance" devices. Bob
  2. BobK

    An easy relay question for some of you "more experienced".

    It is scary how much Google knows about us all. For instance, I have never gotten an ad for one of those devices designed to enlarge a part of male anatomy. ;) Bob
  3. BobK

    Help needed on simple short circuit protection

    No, I have no such experience. But I have never seen anyone worry about a possible short across the terminals of a potentiometer. If this is a product, it is going to be enclosed no? How do expect something to short inside your closed box? And, LIPOs are a different story. They need short...
  4. BobK

    Help needed on simple short circuit protection

    I think you are over worrying. A temporary short from 2 AAA batteries is not likely to do much harm. If anything, it is the batteries that would be damaged. Have you seen cases where this short has destroyed something, or are you just speculating? Bob
  5. BobK

    Does electron die?

    Yep, for each electron you put out, you have get take one back. Sort of like enforced recycling. Bob
  6. BobK

    led/smd rear/tail lighting board problem

    1. Have you tried powered them from 14V which is about what you will get when the truck is running? 2. How many resistors are there? It looks to me like there must 3 or 4 LEDs for each resistor, which means that the difference between 12V and 14V could make a large difference in brightness...
  7. BobK

    Help needed on simple short circuit protection

    Which short are you worried about? If it from 3V to ground, that can be handled in the power supply by current limiting. If it is between the wiper and 3V or ground, that can be handled by a fixed resistor on one side or the other. Bob
  8. BobK

    Sensor for solar irradiance

    Most op amps, including the LM358 cannot output a voltage all the way up to the power supply. Typically it is about 2V less. You need a rail-to-rail opamp, which is a special kind that can output voltages all the way up to the power supply. Bob
  9. BobK

    Linear and non linear system

    Something is linear if it can be modeled by a linear equation, i.e. y = Ax + B Where A and B are constants. Form example, voltage an current in a resistor are linear: V = I R V is y I is x A is R B is 0 Non linear is everything else. For example, the voltage and current in a diode have...
  10. BobK

    How to build SMPS

    Or a logic gate and changes 0 to 1 and 1 to 0. Bob
  11. BobK

    Looking mains voltage in the eye and surviving

    Right, of course. Bob
  12. BobK

    Choosing Wire Gauge

    Yes, because then I would need 150A or 200A in each circuit instead of 15 or 20, requiring probably 4 gauge wire. Ever try to bend 4 gauge wire around a screw terminal? I calculate that 50 ft of 14 ga at 15A drops 1.89 V. At 150A it would be 18.9V, a little high for a 12V system. Bob
  13. BobK

    increasing voltage or current

    The other thing to know is that you will not see much difference between 20mA and 25mA through the same LED. Bob
  14. BobK

    Dumb USB Charger - Just 5v DC & 200 ohm resistor on +?

    It will charge with nothing on the data lines. This is what happens when you plug it into the USB port on a computer. But it will pull a max of 500mA. I charge my iPhone from my computer USB port instead of the 2A charger they provide, just because it is handy. Bob
  15. BobK

    Looking mains voltage in the eye and surviving

    Yes, but make sure the wife and kids (if applicable) are out of the house when doing so. Bob
  16. BobK

    Choosing Wire Gauge

    Yes, that table grossly overestimates the wire gauge needs. If it were true, I would need 4 gauge wire for some of the runs in my house wiring, when 14 gauge works perfectly well. Bob
  17. BobK

    Dumb USB Charger - Just 5v DC & 200 ohm resistor on +?

    These are not the same thing. The 200Ω resistor referred to in the second post is between the two data lines of the USB connector, not between the + power and the connector. And even then, this is not the way charging current is usually signalled, More often the device looks for certain...
  18. BobK

    Is this circuit possible?

    That does not mean that the one the OP has is. Here is the typical circuit: Bob
  19. BobK

    Dumb USB Charger - Just 5v DC & 200 ohm resistor on +?

    As long as the device was designed to charge from a USB port, there should be no resistor. Where did you get the idea there should be? Bob
  20. BobK

    Is this circuit possible?

    READ POST #9 0.2Ω between input - and output -. Bob
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