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  1. BobK

    Question about Transistor

    To be more specific in my answer. In the case of a switching transistor, NPN: You could connect the collector to V+ and the load between the emitter and ground. But in order to saturate the transistor, the base has to be at a voltage about 0.7V above the emitter. So with the full V+ on the...
  2. BobK

    Help figuring out this switching driver.

    Many of the cheap switcher modules on Ebay have a current limit adjustment. These can be used as a constant current supply by setting the current limit to the desired value and setting the voltage limit at the max. Bob
  3. BobK

    Question about Transistor

    Yes. the base of an NPN transistor has to be at a higher voltage than the emitter and the base of the PNP transistor has to be at a lower voltage than the emitter. Therefore, putting the emitter of the NPN at 0V or the emitter of the PNP at V+ makes that possible without having 2 power...
  4. BobK

    Two way motor switch control circuit problem.

    Yep, an on-off-on switch is just what you need. Bob
  5. BobK

    PIC emulator software

    No graphical app, just a simulator than you can run the debugger in. It allows you to step through your program one instruction at a time and look at all of the registers and memory. It also lets you create stimuli on the input pins at specific times. What would you expect a graphical app to...
  6. BobK

    .45 volt supply

    You are wasting your time on something that is dangerous and will never work. The extra energy you get from the hydrogen is always less than what it takes to create the hydrogen. Because the laws of physics, unlike the laws of the state, cannot be violated. Bob
  7. BobK

    Trying to read voltage value from circuit to PC

    Yes, that would be correct. You can get a signal across if the sender and receiver share the same ground. Bob
  8. BobK

    12V battery choice for a 200W solar panel system

    How much energy (watt hours) do you expect to extract from this battery during dark periods? By my calculations it will take 2 sunny days to charge it. Bob
  9. BobK

    Trying Buck Converter on Pspice

    Q1 is configured as a voltage follower. The most voltage you will get on it's emitter is 3V - 0.7V or 2.3V. For a high side switch you need a PNP transistor and the pulse driving the base has to go from 12V (inactive) to 0V (active). Bob
  10. BobK

    triac illumination control circuit for 1000 w lamp

    Commercially available dimmers should do the trick. Bob
  11. BobK

    AVR Programmer, good choice?

    If I were to buy a programmer for AVR microcontrollers (made by Atmel), I would look at Atmel. They have one for $34. Bob
  12. BobK

    PIC emulator software

    The free MPLAB or MPLAB X from Microchip has an excellent simulator built in. My theory on tools for micros is that the manufacturer has much more interest in making them work for everyone than any 3rd party supplier would. Bob
  13. BobK

    transformers back to back - why won't work?

    But if the transformer is not 100% efficient (which it is not) the magnetic flux is not perfectly balanced between the secondary and the primary. Could this not eventually lead to saturation? Consider this scenario. If there is no load on the secondary, the idle current in the primary is...
  14. BobK

    Assistance with Transistor Theory

    Answer: It depends on whether I have a rock of a certain weight or a hill of a certain height. Bob
  15. BobK

    Assistance with Transistor Theory

    If I roll a rock up a hill, it's potential energy increase by mgH. So, is rolling a rock up a hill weight driven or height driven? Bob
  16. BobK

    What components do I need??

    Your best bet is to wait until someone makes a wrist band that is user programmable, then add the features you want in software. Bob
  17. BobK

    [HELP] - Basic AND gate problem

    This reminds me of a story told by my high school physics teacher. On the final exam was the question: How can you measure the height of a building using a barometer? His best student answered: You take the barometer and go up each flight of stairs marking off each length of the barometer on...
  18. BobK

    Suggestions for building a PIC dev. board?

    Yes, that is what I was getting at. Bob
  19. BobK

    What components do I need??

    Take your cell phone apart and look at the size and density of the components. Now think of putting most of that in a wrist band. If you could design and make that, you should be a top designer at Apple. If you think I am dissing you, I don't think there is anyone on this forum who could, by...
  20. BobK

    Suggestions for building a PIC dev. board?

    It is not that difficult to solder a 44-pin TQFP. I have done several of them. It actually takes less time than soldering a 40 pin DIP because you just drag the solder across all of the pins then wick off the excess. You should try it. Get a breakout board of Ebay, look at some YouTube...
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