Search results

Search Forums New Posts
  1. BobK

    Why DC motor draws more current with friction?

    I just did it, and I get exactly the result we have been telling you you should get. With the power supply set to 5V. Running freely, I measure 5V 50mA Pinching the shaft to slow it down partially I get 5V and varying current around 120mA Pinching it to stop the shaft I get 5V and 250mA...
  2. BobK

    Why DC motor draws more current with friction?

    Update: Also tried a 18650, 4.0V unloaded 3.8V when running the motor. As expected, it drops a little due to the internal resistance of the battery. Bob
  3. BobK

    Pin 7 of 555 timer doesn't discharge

    My wife does a lot of work with a picaxe, but I only get involved when a Kubota is needed:
  4. BobK

    Upload code from pic

    MPLAB will dissassemble the code if you can read it. Still not easy to follow, but at least you get instruction mnemonics instead of just hex code. If you can read it, you will be able to program another PIC with the code. But, unless is the exact same part number, it may not work correctly. Bob
  5. BobK

    Why DC motor draws more current with friction?

    Indeed I do. I tried one of my little motors, ran it off a variable 2A supply and I see no drop in voltage when it is is running, either at 5V or 12V (it ran pretty slowly at 5V). Does your supply have a current limit? If so, and it is set too low, the voltage would drop when you run the...
  6. BobK

    Home Security system takeover

    And while you are at it, form some into a hat ;) Bob
  7. BobK

    Voltage Divider vs Series Resistor

    Bottom line: Voltage dividers, meaning two resistors with the output take from their common connection, are not useful for delivering power at a reduced voltage. A series resistor is sometimes useful, when the load current does not vary. For other cases, you want an active circuit, i.e. a...
  8. BobK

    blowing fuses

    You can check your wiring all you want, but if you end up getting it "right" and apply about 14V to something that was intended to run off 6V, it is not likely to end well. Bob
  9. BobK

    Powering a 12v monitor with what battery?

    And there are deep cycle lead acid batteries that are designed to be more capable of running smaller currents for a longer time. These are often used in RVs and boats to supply electrical power. Bob
  10. BobK

    Mobility scooter

    Measuring the static resistance gives you the stall current, which is always higher than the running current. That is why I think it is too low (the resistance is too high). Can you use your multimeter to measure the unloaded running current from 24V supply? Bob
  11. BobK

    Mobility scooter

    3.2Ω. That would indicate a stall current of 7.5A at 24V. That seems way too low to me. If it is correct, a 10A controller would be fine. Bob
  12. BobK

    LED's and constant current

    My point exactly. Bob
  13. BobK

    Simple Motor Controller Circuit

    Never mind. I did not realize you were using an H bridge. Bob
  14. BobK

    Mobility scooter

    I really can't say. I take it you cannot measure the resistance of the motor? Bob
  15. BobK

    Problem with new microphone preamp.

    You can put a resistor between the emitter of the first transistor and the existing resistor/capacitor pair. The gain will be approximately 22K (the collector resistor) divided by the emitter resistor. So 220Ω would make the gain around 100. Bob
  16. BobK

    Heating Jacket controlled by Arduino for Winter

    Theoretically, a battery should produce the same amount of energy whether you are drawing 1mA or 10A from it. But in real batteries that is not the case. They actually produce more energy overall when used a lower discharge rates. When a manufacturer rates the batter for 4800mAH, it is done...
  17. BobK

    hardware learning

    You should just become a hobbyist like me. I have no trouble putting together circuits without knowing what I am doing. :) Bob
  18. BobK

    Heating Jacket controlled by Arduino for Winter

    Just for comparison, 1 liter of kerosene has 10500 WH of energy. So 2 mL of kerosene would give you more heat than your battery. Maybe you should consider a kerosene heated jacket! Bob
  19. BobK

    Heating Jacket controlled by Arduino for Winter

    That battery, if used perfectly efficiently, would give you 1/2 hour of running time. Battery: 4.8AH * 3.7V = 17.76 WH Heaters: 1.5 * 3 = 4.5W * 8 = 36W But battery AH ratings are typically done when used over 20 hours. When used over 1/2 hour it will probably produce 1/2 of that. So 15...
  20. BobK

    Simple Motor Controller Circuit

    No, I meant the diodes, but if you don't have space, you don't have space. Bob
Top