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  1. BobK

    Motor Project

    There are several ways you could go. In order of increasing expense: If you use a simple DC motor you will need some kind of rotary encoder to give feedback about the speed. And optical encoder, or hall effect sensor are typical. In this case you would modify the power to the motor until the...
  2. BobK

    Homemade 10 ohm resistor

    Yes, and I did not say it did not have enough power to run his heater, in fact I calculated that it could run it for 13 minutes. It is more energy that is needed to run it longer since energy = power * time. If he had asked if it had enough energy to start a car, I would have recommended...
  3. BobK

    infrared

    No, because if you make a mistake, it might catch fire in the middle of night and you, and possibly others, might burn to death. Working with mains is not a project for beginners. Bob
  4. BobK

    3+3watt Speaker set DYI need advice!

    Unless you can speak USB and negotiate for more, a USB port on the computer is only required to supply 100mA, which, when multiplied by 5V is only 0.5W. You need 6W. So no, it will not, in general, work. More explanation: To get even 500mA out of your USB port on a computer, you need a...
  5. BobK

    Power supply purchase

    I do like the (most likely unnecessary) heat sinks around the enclosure though. If it is a switching supply, which, from other info it is, it should not need that kind of heat sinking. Bo
  6. BobK

    Homemade 10 ohm resistor

    Your 9V is not going to last more than about 15 minutes discharged into a 10Ω resistor. E = I R 9 = I * 10 0.9 = I That is too much current for a 9v. At 0.5A they have 300mAh, and it gets worse at higher currents, so say 200mAh at 0.9A, or 0.22 hours or 13 minutes. If you use the very...
  7. BobK

    design buck converter with arduino controlling pwm

    Or, you could use a P channel MOSFET. Bob
  8. BobK

    How to use a double slide to control vibrating motors?

    Either would work, but does a 5 position slide switch actually exist? If it does exist you could do it with logic, possibly even just diodes. If it is a potentiometer you will need and ADC. A suitable microcontroller could handle either very simply. Bob
  9. BobK

    PWM signal with 50ns freq. Step

    I first misread you post and posted an entirely useless answer, which I hope you did not read. If I understand you correctly, you want to produce a sine wave with periods (not frequencies) from 250ns to 1uS. To get a period of 250nS you with a 24MHz clock you will have exactly 6 samples to...
  10. BobK

    I need something that is LOUD ,but is still small ,and lightweight. HELP!

    But it only goes to 10 :( Bob
  11. BobK

    Stepper motor control

    The basic driver is an H-bridge for each coil. On a two phase bipolar motor, you would need 2 H-bridges, one for each coil, You then drive them + for first coil + for second coil, - for first coil - for second coil. And that will go one direction or the other, reverse the steps to go the other...
  12. BobK

    How would one make a power supply for a 30,000w xenon lamp

    Alright, you start with 100,000 hamsters. Then each one only needs to generate 0.3W. Bob
  13. BobK

    How would one make a power supply for a 30,000w xenon lamp

    One would not, unless one had a lot of experience, or a death wish. Bob
  14. BobK

    Stepper motor control

    Hi Deimantas, and welcome to the forum. I am a Lithuanian American, my paternal grandparents were born there, so how are things in the old country? I do not have much knowledge of CNC machines, but to control the stepper motors you will need a stepper motor controller board and some...
  15. BobK

    Joule Thief not working

    Did you try swapping the leads of one of the two coils? Bob
  16. BobK

    Placement of batteries (button cells) in the same plane on two sides of PCB

    I understand that the opamps you have chosen may require + and - 6V, but that is not what I was asking. The real question is whether the signals they are processing need to be in that range. Because if all of the signals can be confined to 0 to 3V, you can use 3V rail-to-rail opamps instead...
  17. BobK

    Oscilloscope Newbie

    Or had a trigger level set too high, or had trigger on the other channel, or had external trigger, or had it set for manual trigger. or had some special function activated, or had the vertical gain set too low, or had the time base set at 100 seconds per division, or... DSOs are difficult to...
  18. BobK

    Oscilloscope question

    I sold my analog scope and got a Rigol DSO. Sometimes I am sorry I did. Nothing wrong with the Rigol, but, it is so complicated that I sometimes find myself twiddling for 10 minutes through menus before I find out why I am not getting a trace on the screen. This does not happen with an analog...
  19. BobK

    Flyback or simple boost converter?

    On a normal boost converter (single inductor, not transformer), the breakdown voltage of the switching device has to be higher than the max voltage output since that voltage ends up across the switch (MOSFET or BJT), when the switch is off. What were you using for a switch? What is its...
  20. BobK

    Placement of batteries (button cells) in the same plane on two sides of PCB

    There are opamps that will operate from a single supply of 3V. How are you using them, do you need the whole 12V range? Bob
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