Search results

Search Forums New Posts
  1. BobK

    Fun and games with autotransformers

    I have the answer: Edit: And damn you Steve for wasting 1 1/2 Hours of my time! Bob
  2. BobK

    Motor Project

    If you went for a pre-made stepper controller board, a stepper motor would be simpler to control as Kris suggested. The software to control a stepper motor to run at 1500 RPM would be as simple as putting out 5000 pulses per second. (1500 RPM is 25 revolutions per second, and a typical stepper...
  3. BobK

    Timed Relay Connection/activation

    There does not appear to be an input, it is designed to cycle on when power is applied for a preset time. Bob
  4. BobK

    Timed Relay Connection/activation

    Not the best description I have seen (nor the worst). I interpret this to mean the when you connect 12V to Vcc and Gnd, the relay is immediately switched on. Then, after an adjustable period of up to 200 seconds, it switches back off until power is cycled again. You also have 3 contacts for...
  5. BobK

    PWM signal with 50ns freq. Step

    Each attempt you make to describe what you are trying to do is worse than the last one. Sorry, but you will not get any help until you can coherently describe the problem. Bob
  6. BobK

    Robot servos shaking when registering to a network via radio

    It sounds to me like the PWM signal is not continuing while you are doing the communication. Bob
  7. BobK

    programmable rgb led

    If you simply want to build a circuit that sets the LED to a certain color and then it remains that way, you can use 3 resistors to set the current in the R, G and B LEDs. Bob
  8. BobK

    Negative Thermal Resistance?!?!?

    Still wrong. The average power is not the average voltage * the average current. It is the integral of the voltage * current over time. Say you have a MOSFET that has on resistance of 1Ω (which would be very high for a power MOSFET) switching a 100V supply to a load. It is on 50% of the time...
  9. BobK

    Negative Thermal Resistance?!?!?

    Most of the power eventually shows up as heat in the motors and mechanical linkages that drive the scooter. Unless it is going uphill or accelerating, all of the power is eventually converted to heat. The power dissipated by the MOSFET consists of two components. When the MOSFET is on, it is...
  10. BobK

    Negative Thermal Resistance?!?!?

    All true. What I meant is that it does not eliminate the need for a large heat sink of some kind, it just moves it somewhere more convenient. bob
  11. BobK

    Negative Thermal Resistance?!?!?

    Neither of those really helps, since you still have to get rid of the excess heat somewhere. All the can do is move it to another place. Bob
  12. BobK

    programmable rgb led

    You are not really programming anything, you are constantly turning each of the R, G, and B LEDs on an off, with the % of off time controlling the color. This is a dynamic process that must continue to go on if the color is to remain set. A microcontroller is by far the simplest hardware you...
  13. BobK

    Motor Project

    Here is a picture of my robot vehicle with DC motors and an photo-interrupter to get feedback of the wheel speed. The toothed wheels and the little black U's behind them are a photo-interrupter, which sends a pulse each time a tooth interrupts a light beam going across the U. You may notice...
  14. BobK

    Transformer Output Current

    The 3A should be the rating at 36V. If a transformer is rated at twice the current at half the voltage, that is because it is limited by the magnetic field in the core. The magnetic field is related to the current times the number of turns. If you use only one side of the coil, for 18V you...
  15. BobK

    LED limit with zener.

    It should not take any more wires going into the globe to put them in parallel. Just run two wire from outside to the first one, then two wires from the first to the second. Bob
  16. BobK

    design buck converter with arduino controlling pwm

    I have successfully used a P channel in a buck converter that takes a 19V laptop brick and provided constant current (1A) to charge NiCad batteries in my drill/driver. The only thing needed to drive it was a PN2222 used as a level converter. And a micro to do the PWM and monitoring. In lower...
  17. BobK

    Negative Thermal Resistance?!?!?

    Case to ambient is used when there is no heatsink. All you have discovered when your calculation goes negative is that you cannot dissipate 150W without a heat sink and keep the junction temperature where you want it. Which is no surprise, since the limit for a TO220 for example, is about 1W...
  18. BobK

    MOSFET mystery

    This thread is a testimony to the kind of results you can get when a problem is stated clearly and presents all the relevant information. Good work all. Bob
  19. BobK

    PWM signal with 50ns freq. Step

    So I guess he really want to generate a sign-wave, not a sine-wave. :eek: And funny how the clock frequency and periods (whatever they mean) change from post to post. I give up. Bob
  20. BobK

    Getting Started with FPGAs.....

    Hi Fish, I too am interested in FPGA and would like to develop my own CPU within one, once I retire next year. I would like to hear your experience. Perhaps you could start a project log when you get started. The company I work for made a multi-core network processor with a internal tool...
Top