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  1. BobK

    Rechargeable A.C.

    How long do you expect it to run on batteries? Bob
  2. BobK

    Joule Thief

    Try switching the leads from one of the coils in your transformer. They must be connected correctly for the Joule Thief to work. Also, typically you would use more windings that that. The one I built used 22 turns of enameled wire. Bob
  3. BobK

    Help with battery packs

    A battery will be rated in mAH (milliamp hours) or AH (Amp Hours). Since you have two lights that draw 4A, your battery will have to have about 12AH (or 12000mAH) in order to run the lights for 3 hours. I would look at 3S Lithium batteries that are nominally 11.1V. Bob
  4. BobK

    Help designing an Inductor

    And I predict he will not. Bob
  5. BobK

    PIC 1.5V Output

    Look at chapter 17 of your datasheet. There is a 5-bit DAC that can be output to a pin. With your 5V supply as the reference: DACR = 10 would give you 9/32 * 5 = 1.56V But, as GRYD3 points out, this is only as a signal, it cannot supply any power. Bob
  6. BobK

    Rechargeable A.C.

    A small window air conditioner takes about 500W of power. That is going to be a lot of battery. Bob
  7. BobK

    Capacitor and inductor reactance

    Yep, at 50mH the answer in the book is right. Bob
  8. BobK

    blew a resistor and cant tell what it is for a 4 led battery indicator i got from an old PW toy

    Well, it would take 50V to exceed the limits of a 10K 1/4 W resistor. 24V across a 10K resistor is only 0.06 W. Bob
  9. BobK

    Low voltage, high current boost converter IC

    And a boost converter at that kind of current is going to require a large inductor. If all you are doing is heating, why use a boost converter anyway? Why not use a heating element that works at the battery voltage? If it works at the low end of the battery voltage, you can use PWM to lower...
  10. BobK

    Lighting Conversion Help

    It sounds like you bought much more than you needed, unless you need to run it off AC line voltage and change the colors. If you just want them for lighting, get strips of white LEDs designed to run off an auto electric system. Bob
  11. BobK

    12VDC to 100DC is it possible?

    Actually, the engine is not tiny, it is 1.8L, and the car almost never runs completely off electricity. What Toyota did was use every trick they could think of the get the highest efficiency: An Atkinson cycle engine that is run at a constant RPM where it is most efficient when it is not...
  12. BobK

    Please help with replacing electromagnetic buzzer

    I would use a rectifier to supply a signal to a transistor to switch a 3VDC supply to the buzzer. Bob
  13. BobK

    Adc Value Conversion

    Well, I told you to use float variables for the calculation, didn't I? Do you understand the difference between int and float? Bob
  14. BobK

    12VDC to 100DC is it possible?

    Lower the voltage does not help. The motor will need some amount of power to run that car at a given speed under given conditions. It would still need the same power with a lower voltage. In fact, all you would be doing is limiting the speed of the car, which you can presumably already do...
  15. BobK

    The input given to Piezo Speaker is an analogue signal or Digital signal?

    No, it should sound continuous, unless you are turning the 100Hz sine wave on and off at some lower frequency. What do you expect it sound like? Bob
  16. BobK

    Adc Value Conversion

    Let Mc = the calibration mass Let Az = the ADC reading at 0 gm Let Ac = the ADC reading at calibration mass Let M = the unknown mass Let Am = the ADC reading of an unknown mass Then the linear approximation would be: M = Mc * ( (Am - Az) / (Ac - Az) ) Whether or not this linear approximation...
  17. BobK

    12VDC to 100DC is it possible?

    Yes. The difficulty will depend on how much current you need. Also why is it 100V in the title and 72V in the post? Bob
  18. BobK

    Help with heater

    A resistor is definitely not the way to go. In order to reduce the power from 800W to 400W the resistor would dissipate 400W! Most likely, they used to diode to get the 400W setting. A diode will pass only half the waveform and therefore half the power. If you are in North America, (120V...
  19. BobK

    Help with Transistor testing

    Does you multimeter have a diode setting? Bob
  20. BobK

    IR LED off of 24V rail - Best way to do it?

    If you are running an IR LED, which needs about 1.3V typically, why convert down to 5V? Why not something smaller? Bob
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