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  1. BobK

    High amperage DC-DC down conversion

    I suppose you could also use a solid state relay as the switch in a buck converter, but it would not be ideal, unless it was basically just MOSFET. Bob
  2. BobK

    Protecting DC Output SSRs against inductive kickback

    The current from the indcutor has to find a path. This may include blowing out semiconductors. Bob
  3. BobK

    Adding voltages

    Look up op-amp summing circuit. Bob
  4. BobK

    12 volt voltage "clamp?"

    If you could break open one of the LED modules, it might be no more difficult than changing out a resistor. If you could post pictures we might be able to help. Bob
  5. BobK

    Mad resistor bands.??

    As shrtrnd already said, silver in the 3rd band is a multiplier of 0.01, which means brown black silver is a 0.1 Ohm resistor, which will probably read as 0 on your multimeter even if it is not shorted. Bob
  6. BobK

    Analog & Digital Electronics both have advantages

    Digital is Good, Analog is Evil. Except at high enough frequencies, both are Evil. Bob
  7. BobK

    Light house flasher

    Actually, you should use a solid state relay, which is designed for exactly this purpose. Get one that is opitcally coupled and designed for 120V AC at a current above what you need. The control line actually drives and LED so you can use your LED flasher as is! Bob
  8. BobK

    AA & AAA Battery Question

    No, the charge rate is usually a multiple of the capacity. Higher capacity batteries can be changed with more current. For example if a battery can be charged at 1C then it will take a bit over 1 hour to charge it no matter what its capacity. Bob
  9. BobK

    Amplifier problem

    Looking at that circuit I seriously doubt that it puts out anything like 1 Watt. There is a 50 Ohm resistor in series with the speaker. If the speaker is a standard 8 Ohms, it sees only 8/58 = 14 percent of the voltage swing, and that is limited to 9V p-p or about 3V RMS. So the speaker sees...
  10. BobK

    AA & AAA Battery Question

    + capacity
  11. BobK

    Atmel Chip Programmer

    I have not used Arduino, but I think I can safely say that any programmer capable of programming the chip can put the bootloader on it. This of course assumes that you have the booltoader hex file. Then, to use the Arduino software, you need a way to download programs onto the chip using USB...
  12. BobK

    Atmel Chip Programmer

    http://store.atmel.com/PartDetail.aspx?q=p:10500054 I am a PIC guy, so I have no experience with this, but I would highly reccommend getting a cheap programmer from AVR. If they are anything like PIC using any 3rd party one is asking for trouble. Bob
  13. BobK

    The Trouble with Transistors

    The relay coil goes where Rc is (that is in place of Rc). To calculate Rb you start with the desired base current. This the the collector current / beta, because beta is the ratio of collector current to base current. But them multiply this by 2 to make sure the transistor is in full...
  14. BobK

    Backasswards Capacitor

    Are you sure you are describing the circuit correctly? I simulted it and it does nothing, i..e. the voltage fed to the comparator is the same as the input AC voltage. On the other hand, if the capacitor and resistor are in parallel, i.e. one side of each of them is connected to ground and...
  15. BobK

    LED reduction Resistor

    The heat is the same whether is it done with a resistor or an LM317. The LM317 can control the current more effectively, but, as I said before a resistor is just fine, people use them in even much higher current applications. Bob
  16. BobK

    LED reduction Resistor

    LEDs are better driven by a current source than a voltage source. Look in the LM317 datasheet for the configuration of that device as a current source. Although, at 30ma, a resistor is fine. Bob
  17. BobK

    how to signal an alarm at point

    You can patent an idea, but you have to give enough information for someone skilled in the field to build it. I think your best bet is get someone under NDA to research it for you. On the other hand, you could probably give us enough info to be of some help without disclosing the even the...
  18. BobK

    how to signal an alarm at point

    There is no such component, it would be a circuit based on several components. The problem is that there is no one way to determine the distance between two objects, which one is best would depend on how far apart they might be, whether they are within line of sight etc. So the information you...
  19. BobK

    Recharging a car battery

    Do you realize that there will be a braking effect when the motor is used as a generator? So the robot is no longer coasting. Perhaps this is desirable, perhaps not. Bob
  20. BobK

    Rechargeable batteries input

    Here is a great resource for info about batteries: Battery University/ Bob
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