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  1. BobK

    Tweaking an industrial ozone generator help (HV)

    You are missing the point. You cannot reduce the current while maintaining the voltage. Bob
  2. BobK

    Locking cat door, really need some help...

    Or you could power an electric fence from the switched outlet. Bob
  3. BobK

    Tweaking an industrial ozone generator help (HV)

    That will not work, the voltage would be reduced drastically and it would not operate. Easiest way to make it produce 1/10 of the ozone would be to operate it 1 /10 of the time. Bob
  4. BobK

    wanting to make a portable mini bluetooth audio board

    The supply voltage for the bluetooth audio board is 5V. Do not try to use the 12V battery pack Grazzje linked to, get one of the 5V ones that are sold everywhere. Bob
  5. BobK

    Shift Register weird response

    It sounds to me like you do not have a common ground for the two circuits. The ground of the Rasp Pi and your shift register circuit must be connected together. Bob
  6. BobK

    Transformers

    Yes, you can convert 29V to 12V using a DC to DC converter. But one thing you must check is whether it can supply enough power for all the devices, taking into account that maybe 20% is lost in going from 29 to 12V. So, add up the power utilized by all 4 devices. Power for each is voltage x...
  7. BobK

    Project for interested novice that will give him most taste of electronics?

    IMHO, your approach is wrong. You don't learn by starting out with a large complicated project. Even if you manage to complete it, you will not have an understanding of it. And more likely, you will give up in frustration. You learn by starting with small circuits and trying to understand...
  8. BobK

    PCB Artwork Orientation?

    Had to open Eagle to refresh my memory since I do not use it normally. To print the bottom layer, you would go to view, and under layer settings, push "none", then select bottom, pads, vias, and dimensions. That should show everything that will be copper in the right orientation. Bob
  9. BobK

    PCB Artwork Orientation?

    If want the bottom layer, you print it as if you are looking through the board from the top. Then you place the printed side of the transparency against the board when exposing. For the top layer (which I never do, I only make 1 layer boards) You would have to flip it first. Bob
  10. BobK

    Pokemon Go

    Hey, it cured Morticia's Candy Crush addiction. Sort of like going from alcohol to heroin. Bob
  11. BobK

    Microcontroller project for my pool pumps

    And you get 0.6Ω for the coil? Then I would submit that the coil is shorted out. It looks to me like you have one working contactor and a second one with a shorted coil. Bob
  12. BobK

    Three phase oscillator

    Tell us what you are trying to do. Bob
  13. BobK

    wanting to make a portable mini bluetooth audio board

    Easiest way is to use one of the many rechargeable "power banks" that are commercially available for less than you can build one. And they can be purchased in a wide range of capacities. Bob
  14. BobK

    Microcontroller project for my pool pumps

    What does your meter read when you short the leads together? Bob
  15. BobK

    Dodgy Chinese flip flop...or my circuit?

    It is impossible for an input to be at the correct voltage but not enough current. If it cannot supply the correct current, the voltage must drop. In other words, if you supply 3V to the base of the transistor from a battery and the relay closed, then the "flip flop" supplies 3V to the base...
  16. BobK

    Microcontroller project for my pool pumps

    The resistance will not tell you how much current is drawn for an AC coil. But, based on the low resistance reading, I think the terminals have been identified wrongly. Bob
  17. BobK

    Battery doesn't power microcontroller as expected

    I would expect 40K and 100nF (.1uF) to work. So maybe something else is wrong. Datasheets for PIC microcontrollers generally have schematic for the minimum hardware configuration. I could not find same for your TI part. Do you have any smaller capacitors? In the range of 1 to 50nF? Also...
  18. BobK

    Stepping down speaker input to line level

    You are right Chris. I think maybe an 8 pole active bandpass filter using 4 Salen-Keys stages is required. Chebyshev response of course. Bob
  19. BobK

    Stepping down speaker input to line level

    Line level is about 1/2V peak. Your 5W speakers are about 6V peak. So I would reduce the voltage with a voltage divider by a factor of 10 or so. I.e. 10K to the output 1K to ground, junction to the input. Bob
  20. BobK

    Battery doesn't power microcontroller as expected

    And, looking at the lanchpad schematic, it has a 47K pullup and 10n capacitor to ground. Bob
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