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  1. BobK

    circuit calculation

    You could do that, but is it not optimal. You will waste a lot of power in the resistor, particularly for the lamp. But the calculations go as follows: R = (Vb - Vl) / I Where R is the resistor, Vb is the battery voltage, Vl is the lamp (or LED) voltage and I is the lamp or LED...
  2. BobK

    Table football flippers

    You are looking for either a solenoid or a linear actuator. Bob
  3. BobK

    What are development boards for?

    Assuming the hardware around the chip is correct, the program will run in the new circuit. This is how I did my first PIC project, but after breaking a pin off by plugging it back and forth between the development board for programming and the final circuit board about a hundred time, I started...
  4. BobK

    What are development boards for?

    They are mainly for learning. You can program the chip and interact with whatever peripherals the development board has without having to build any hardware yourself. I started PICs with the low-pin-count development board from Microchip. And I used it to program the chip for my first...
  5. BobK

    Cree Led Conversion

    It is really not all that involved. All you have to do is replace the board that connects to the two red wires with a single resistor. The resistor is calculated via the formula I gave once you know the specifications of the red LED that you are using. Bob
  6. BobK

    Stepper control using PC

    You can get USB GPIO boards that would allow you to send signals to stepper motor drivers from a PC. Bob
  7. BobK

    Inverter Circuit Help

    To get 2000W at 18V you would need a transformer capable of 111A. 120A for a little margin. Bob
  8. BobK

    alarm clock with led - with your help

    I actually do not think it would be all that good since it varies so slowly that it is difficult to tell the difference between colors an hour apart. For your purpose I would modify it to have an exanded scale, i.e. go through all the colors in the shorter period that you are interested in...
  9. BobK

    5 Pins Micro USB Pin Out

    The article I linked to tells you exactly that. Bob
  10. BobK

    How to allow load function only once

    Well, your post did not really give enough information to make a suggestion, I cannot figure out what you are trying to do. First you talk about 1 or 2 seconds and then stop, then you mention a 60 second delay. You said nothing about what triggers the 1 or 2 seconds of on or where the 60...
  11. BobK

    alarm clock with led - with your help

    I built an LED "clock" that changes color throughout the day. You can tell what time it is within about an hour by the color of the light. But that is not what you are asking for. For your requirements, a micro controller would by far be the easiest solution. You would need a way of...
  12. BobK

    5 Pins Micro USB Pin Out

    Or look at the wikipedia article. Scroll down to Pinouts. http://en.wikipedia.org/wiki/USB Bob
  13. BobK

    Cree Led Conversion

    So it looks like it is simply using a resistor to limit the current. In that case, you should just replace the resistor board with a series resistor calculated based on the new red LED. The equation is: R = (Vb - Vf) / If Where Vb is the battery voltage, Vf is the foward voltage of the...
  14. BobK

    Cree Led Conversion

    The picture does not help much, I was hoping to see a circuit board. Bob
  15. BobK

    Cree Led Conversion

    Simply replacing a white LED with a red one may or may not work depending on the dirving circuitry. The forward voltage of the white LED is likey 3.3-3.6V whereas the red one is going to be about 2.2 to 2.5V. So you might simply blow it out if you replace it with no other modifications. If you...
  16. BobK

    What Is the difference between capacitance and voltage ?

    C = q / V Capacitance is not voltage, it is charge divided by voltage. Capacitors with different capacitance will have the same voltage when storing different amounts of charge. And there is no max voltage for an ideal capacitor, there is for real capacitors when they physically break down...
  17. BobK

    PCBExpress Help

    +1 I have used ExpressPCB and find it the easiest software to use. I use it for my DIY boards. If it could export Gerber files, I would use it for most everything. Adding new components and footprints is a snap, since you can easily start with any existing component and modify it as needed...
  18. BobK

    Program for drawing schematics?

    Fair enough, and I use it only because of 5 (Osh Park takes the files directly) Let me respond with what I don't like. 2) The way the libraries are organized is ridiculous, it is very time consuming to find anything in the libraries. For instance, the only way to know if you have selected...
  19. BobK

    PCBExpress Help

    Not sure about PCBExpress, but in most PCB CAD programs you can make your own footprints. It is not that difficult. Bob
  20. BobK

    Program for drawing schematics?

    Really? I find it one of the most annoying tools I have ever used. Bob
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