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  1. dorke

    Need help on the evaluation board of a capacitive readout chip

    FG is Frame Ground ,also called chassis ground. It is used in analog or mixed analog/digital circuits to prevent noise interfering with the circuit, and EMI/RFI suppression in/out of the circuit. What is this circuit doing?
  2. dorke

    Convert DC to AC

    You can start here
  3. dorke

    Variable capacitor

    Chris, You are correct, absolute zero capacitance is never reached . The BB112 capacitance range is 18-500pf for Vr in the range 1-8Volt. That range covers much more than needed in this app. (85-365pF)
  4. dorke

    clever vibration motor driver?

    Hop, Bob Pease was an icon. Definitely, an "Analog World " hall of fame member, with Jim Williams and probably the greatest of all Bob Widlar. Their genius creative minds made the famous pioneering Analog companies invent and "tick" (Fairchild,National-Semi and Linear-Tech.):) Here is a...
  5. dorke

    Variable capacitor

    o.k looks like you are using this circuit. The tuned frequency as an L*C term in it. So "naively", if we change C from 365pF to 30pF (lowering by a factor of 12.17). we need to use 12.17*L instead of the value used before (i.e for the 220uH use 12.17*220uH=2.7mH etc.) note, that "naive"...
  6. dorke

    Variable capacitor

    It isn't strange at all they are obsolete: They are very big,expansive,mechanical, and... No body needs them(almost)...;). In small analog transistor radios they are still used,but the capacitance is much smaller about 30pF. There are many ways around: 1.Use a varicap. 2.Change the design to use...
  7. dorke

    Variable capacitor

    If you need to tune your receiver to different frequencies you need the variable capacitor. Instead of the mechanical air type you can use a varicap. The variable air cap. your circuits uses 365pf has huge physical size. This kind is quit obsolete now days.
  8. dorke

    Access Control Turnstile Gate - Need help with circuit

    This sounds to me as a dangerous endeavor. People are going to pass through that gate and electric safety regulations and approval are mandatory. I suggest you contact the manufacture and let him "bring to life" and install that gate. You don't want or need the responsibility of somebody getting...
  9. dorke

    Coil with iron core as a generator

    Generally, for a given coil shape: the factor that matters is the magnetic permeability of the core μ. The larger the μ, the larger the induced voltage. You should use iron core, and you can make it yourself.
  10. dorke

    Filter Choke for power supply

    For relatively low currents the usage of resistors instead of inductors in filtering is fine. 6ma is low current. a resistor of 1k will drop 6v on it ,and dissipate very little power (0.036W). If that voltage drop is o.k with you than go for it(You hasn't specified the allowed ripple yet)...
  11. dorke

    Filter Choke for power supply

    Y2KEDDIE, Let's start at the beginning ,shall we.o_O What Current does your PS need to supply? What is the allowed ripple? The above is absolutely needed in order to give you a solution.
  12. dorke

    Bringing to life and making use of LCD TV back-light and inverter

    The only thing I can say about this idea: it is not a very good one.:rolleyes: You need lighting? Do it with LEDs !!! they have "the best of all worlds features" , everything that you don't have with CCFLs.
  13. dorke

    Electronic Metronome

    Probably the most useful triangular wave is the saw-tooth wave, it is used in seep oscillators and in the time base horizontal sweeps of crt analog scopes. There are other,rater rare,uses of triangular waves in signal processing
  14. dorke

    Controll for Seven-Segment-Displays

    And,you can get the STLED316S from mouser (not very cheap!). I'm sure there are other suppliers as well.
  15. dorke

    20kv Cockroft walton generator

    John, 1.I have a bit different term for the voltage drop. Voltage drop ∆V = iload *(2/3 n³ + n²/2-n/6) / [f*c] for n=20 we get ∆V(about )=5500*iload / [f*c] you need to fill in f and C to get iload or vice versa. 2.Take very good care not to get yourself zapped! 3.The voltages of the...
  16. dorke

    clever I2C/SPI switch: fail

    1.You only need to switch SDA no need to do that for SCL (assuming your MCU provides SCL i.e is master). 2.What you need is the simplest 1-line(SPST) analog switch. You can do that with very cheap Mosfets and a control line from the MCU... or use a 74HC4016 ,CD4066 etc analog switch.
  17. dorke

    Samsung LED TV UN39FH5000F screen issues

    You don't need to break anything...;) Start with the Samsung remote Support ,it may be very helpful. You can also contact them via e-mail the details are on the same page. If needed ,come back here as well.
  18. dorke

    Electronic Metronome

    The easiest way would be with a 555 timer, plenty of circuits on the web...
  19. dorke

    LQFP48 footprint

    That is hard to believe ! Which manufacture ?
  20. dorke

    Dumpload system

    That is strange.o_O The heaters used in water boilers are intended for continues use and long life(3 years and above ). Most probably they are not cooled properly and that shortens their "life" ! Did you make any temperature measurements of the water near the heaters? Are the heaters submerged...
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