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  1. BobK

    Dumb question re. simple inverter

    No, that is not a problem with my explanation. I said that it uses a high speed converter to convert to 170V DC, then inverts that to AC. This second step would obviously be at 60Hz. The difference is that this step does not require a transformer. Bob
  2. BobK

    2 pole low frequency shelving filter design

    I don't see how that circuit does any filtering. Bob
  3. BobK

    Salvaging Parts

    You are right about Radio Shack. Try Ebay for common components. You can get 100s of LEDs for a few dollars. Digkey and Mouser are good for components that you cannot find on Ebay. Edit: For instance, want some SMD resistors? You could desolder 2500 of them, or, for $8 you could get all of...
  4. BobK

    MP-PAM series capacitor overvoltage detection cct

    Can somebody link to said circuit so that we don't have to search for it? Bob
  5. BobK

    Dumb question re. simple inverter

    The low weight inverter probably works by using a high speed switching boost converter that produces about 170V DC and a MOSFET bridge to invert it to AC. The transformer (or just inductor, depending on the circuit) can be much smaller because it runs at a frequency of probably 100KHz or more. Bob
  6. BobK

    Need help with calculations for a ribbon speaker cable!

    Wow, just looking at those scope pictures makes my ears ring (at 4MHz). Bob
  7. BobK

    Wiring a Counter

    You can cut off any plug you want to get exposed wires! Or you can make up a socket for it if you want to be able to unplug it from the adapter. Bob
  8. BobK

    Need help with calculations for a ribbon speaker cable!

    To a man who can hear 500KHz, it might make a difference. Bob
  9. BobK

    Wiring a Counter

    Most wall warts are DC output. Look at he one linked in post #7 for example. Bob
  10. BobK

    Active Bridge Rectifier?

    Let me see if I understand what you want. You have a PWM signal that is 1V with a variable duty cycle. You want to detect that there is a PWM signal present of any duty cycle and put out a constant 1V when it is present. If this is the case, you could use a monostable circuit that is...
  11. BobK

    i need help in putting together a sound machine with a lcd control panel

    If you have no electronics knowledge whatever, including programming, it would be like trying to build a race car with no mechanical knowledge. However, if have excellent programming skills, you might be able to put something together with a Raspberry Pi and an LCD panel with an HDMI...
  12. BobK

    ? about forcing motor to turn in the opposite direction to powered rotation.

    It might also damage the power supply. Bob
  13. BobK

    Wiring a Counter

    A 6 digit LED display is going to drain any small batteries pretty quickly. Is there a reason it has to be battery powered? If not, the wall-wart is a much better solution. Bob
  14. BobK

    Salvaging Parts

    Salvaging components that cost pennies or less is not economical. For example, here is a kit of components that you might actually use: http://www.ebay.com/itm/Electronic-Parts-Pack-KIT-for-ARDUINO-component-Resistors-Switch-Button-HM-/181496980423?pt=LH_DefaultDomain_0&hash=item2a421023c7...
  15. BobK

    buzzer amplify

    Actually, after thinking about it for a bit, you need a push-pull stage to amplify for the piezo, because it is basically a capacitor. I cannot think of a reason why my idea of bridging 2 outputs did not give you a significant increase in volume, unless the code was incorrect. Can you post...
  16. BobK

    Police Lights Problem

    As multiple people have said, your circuit appears to be correct. The error must be in the build. Bob
  17. BobK

    Capacitors instead of batteries.

    Okay. 6V 400mA it is. The equation for a capacitor discharge is: dV/dT = I / C So, let's say you have charged your capacitor up to 6V and the pump will still run reasonably at 5V. This means you will discharge the capacitor from 6V to 5V over 2 minutes. dV / dT = 1 / 120 So: 1 / 120 =...
  18. BobK

    Capacitors instead of batteries.

    Okay you answered one of my questions, and apparently cannot answer the question about the solar / turbine. But you did not tell me what voltage and current your pump needs. I need to know this in order to calculate what you need in terms of capacitors. Also, you refer to batteries being...
  19. BobK

    How to draw regulated 5 V or 3.3 V from LED driver

    How much current do you need for the micro and associated circuitry? Is the driver a current source? If so, what is the current setting? Bob
  20. BobK

    Police Lights Problem

    Try hooking up an LED to one of the unused output of the 4017 and see if it flashes in a regular pattern, at 1/10th the speed of the input as it should. I am wondering if there is some noise triggering the 4017. Bob
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