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  1. BobK

    What components do I need??

    I hate to be the party pooper, but you are dreaming if you think you could build such a thing. Bob
  2. BobK

    Mains voltage transistor switch?

    Nope. What you want is a solid state relay. These are optically isolated so that the high voltage cannot get into your low voltage circuit, and typically use triacs for AC switching. Bob
  3. BobK

    transformers back to back - why won't work?

    A transformer core is being constantly magnetized and demagnetized following the sine wave of the input. But the core can only magnetize to a certain level. After that, it stops being an inductor and acts more like a resistor, and way too much current can flow. So if the load is trying to...
  4. BobK

    Suggestions for building a PIC dev. board?

    Okay. I would not limit it to 8-pin PICs, you would run out of pins before you get to your third project. Even 28-pin ones get to be short on pins if you are trying to run a 7-segment display. If I were doing this (and I have been thinking about it) I would use a 44-pin TQFP because it has...
  5. BobK

    Suggestions for building a PIC dev. board?

    What is your purpose in making this "development board?" Are you talking about something that can take multiple different PICs and write an debug code, then put the PIC into place on a custom board for the final product? Or are you talking about a board that will have multiple capabilities and...
  6. BobK

    200 AA Batteries to make a portable power supply

    Look into deep cycle sealed lead acid batteries. These will have an amp hour rating. Since they are 12V, you multiply by 12 to get a Watt Hour rating. For example, a 35AH battery is 420 Watt Hours. If you music system uses 50W this would last about 8 hours ideally. But an inverter is going...
  7. BobK

    Simple project needed

    A single transistor would probably do it. Bob
  8. BobK

    Where to buy components?

    On line sales have pretty much decimated brick an mortar electronics suppliers. I recently went to the only store I can find in the Boston area and it was a big disappointment, hardly better than Radio Shack for components. On the other hand, Mouser almost always ships my order the same day...
  9. BobK

    Power up 2 circuits in parallel with one source

    Why would you want to use 18V when the max voltage you need is 9V? All that does is waste half the power immediately. I know the Arduino boards take 9-12V but they actually run this through a voltage regulator to get 5V for the microcontroller. Is there a 5V input as well on your board? You...
  10. BobK

    200 AA Batteries to make a portable power supply

    Yes, but only if play only songs by AC/DC. :D What you need is a 12V battery (like a car battery) and an inverter. Bob
  11. BobK

    how a simple bit/data synchronization work?

    The simplest method of synchronization is used in serial asynchronous data transmission, usually just called serial lines. This works by keeping the logic level in one state (typically high) when no data is being transmitted. Then, to transmit data, the line goes low for clock 1 period (this...
  12. BobK

    silly idea

    The unique thing about a quantum computer is that the Qbit can be 0 and 1 at the same time. Sure, you can simulate by making an exhaustive search of all possible combinations of Qbits, but that would not shed any light on how a quantum computer works. The quantum computer essentially does this...
  13. BobK

    Boost Converter with mc34063

    R1 looks like it is functioning as a current sense resistor. If it is wrong, the chip is going to cut off the current at the wrong time. You need to get a power inductor rated at higher than the peak current (which is going to be higher than your output current). It I highly doubtful that the...
  14. BobK

    assembly Instructions

    Steve, He is trying to design hardware to execute the 8051 instruction set. And he has wants us to teach him the basics of computer architecture, one forum post at a time. I understand someone has tweeted "War And Peace". His quest is similar to asking us to do that. Bob
  15. BobK

    Newbie in great need of help ! ! !

    Yes, two cell phones and a app are what is needed, and would do this far better than anything you could build for less than the price of the cell phones. Bob
  16. BobK

    Assistance with Transistor Theory

    I knew I should not have stepped into this thread. Bob
  17. BobK

    single polarity voltage supply

    Duke's suggestion is using a single 9V supply. What is your problem with it? Bob
  18. BobK

    Cordless 1500 Watt Hand-held Blow Hair Dryer

    Electric cars require huge batteries because the energy/weight ratio is much lower than gasoline. So I propose a gasoline powered hair dryer. Burning gasoline (or another liquid fuel) would provide the heat directly, 100% efficiency. And a small gas engine like the kind used in model aircraft...
  19. BobK

    Assistance with Transistor Theory

    Where is the current control? Um, the equation for Ib in terms of Ic perhaps? To me, voltage control would mean that Ic would be related to Vbe in some equation. None of Adams equations does that. The only place Vbe comes into these equations is using an approximate value of 0.65V in order...
  20. BobK

    silly idea

    Quantum computers exist only in highly sophisticated physics labs and even then are very limited. They cannot be built from conventional electronics, They rely on the quantum states of individual atoms. Not ready for home use yet. Bob
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