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  1. AnalogKid

    Limiting inrush current without power loss?

    A polyfuse is the opposite technology - it starts out at a low resistance when cold, then snaps up to a high resistance above a thermal trip point (that is tied to a certain current level). ak
  2. AnalogKid

    passive WIFI

    Actually, no one said that. In fact, this technique does not "generate" anything. That's the point. A chronic problem with hotel and motel key cards is the extremely low magnetic coercivity of the magnetic stripe. It is easy to re-record, which makes it easy to erase. So easy that merely...
  3. AnalogKid

    Limiting inrush current without power loss?

    If a PWM circuit won't "fit in the housing", I doubt a relay will, with or without its control circuit and coil driver. Before soft-starting PFC circuits because so common in industrial power supplies over 1 kW, a common technique was a NTC limiter combined with the shorting relay. This has a...
  4. AnalogKid

    Limiting inrush current without power loss?

    Negative Temperature Coefficient (NTC) thermistor. There are many designed specifically as inrush current limiters...
  5. AnalogKid

    EEG circuit - need help please!

    Coming along nicely, much better than where you started. You may have scaled the three filter network impedances down too far. Since this circuit will be inside a 100% shielded enclosure, you don't need an extra low impedance to control noise pickup. According to the high-end audiocrazies...
  6. AnalogKid

    dual power supply for large countdown timer?

    That is called a center-off toggle or rocker switch, sometimes noted as ON-OFF-ON on a configuration chart. Something to consider is adding a 12 V relay, powered by the output of the AC supply. This way, the system changes over automatically. Wnen AC power is present, the system uses it even...
  7. AnalogKid

    Where can I find 78H12, 78H15, 79H12, 79H15? Or something similar?

    Since Pb is the symbol for lead, these probably have a lead-free plating on the leads (NOPB = no lead). Also called RoHS compliant - reduction of hazardous substances (or sonething like that). ak
  8. AnalogKid

    More Range From 10 turn POT

    Your question is very low in detail. More range - more than what? What is the "range" now? AND, kinda important, what range do you want? IF you are saying that the circuit output goes from minimum output to full output in only 1 turn of a 10 turn pot AND IF you are stuck with that 10 turn...
  9. AnalogKid

    Guitar Electronics .

    Why?
  10. AnalogKid

    Killing SSR (relays) - Need to understand

    Also, the heaters might be producing an inductive kick when turned off. A 240 V or 277 V transient suppressor across the output won't hurt. Many SSRs turn off at zero crossings and that should reduce this effect, but without more information this is a reasonable guess. ak
  11. AnalogKid

    Where can I find 78H12, 78H15, 79H12, 79H15? Or something similar?

    Linear Technology and National Semiconductor (now owned by TI) make positive and negative 5 A regulators. Do they have to be fixed, or can you use adjustable parts like the LM338? ak
  12. AnalogKid

    741 Op-amp

    Nope. An LM324 is four opamps in one package sharing common power supply inputs. The pinouts of the two devices are not at all alike, and one cannot be substituted for the other in a circuit already built. Also, the two amplifiers are not alike. None of the opamps in an LM324 have offset...
  13. AnalogKid

    Kinetic Phone Charger

    So the kinetic device isa moving-magnet generator? If so, then we need a schematic of the circuit. ak
  14. AnalogKid

    digital clock

    There a zillion digital clock projects and schematics on the innergoogle, so you have to narrow things down if you expect any real help. For example, CMOS or TTL chips? LED, LCD, or Nixie display? Seconds display? Alarm? ak
  15. AnalogKid

    Novice designing circuits

    Can you at least give us a vague area of operation? RF, small dc power supplies, audio, video, temperature sensing or other industrial control, LED drivers, motor speed control, little computerized gadget, MP3 player, space shuttle, other? Also, are you looking for a design service only...
  16. AnalogKid

    EEG circuit - need help please!

    Only you can specify the overall circuit gain. Once you have that, divide it by any fixed-gain stages like the two filters. Whats left is the gain required of the diff amp, and there is an equation for that in the datasheet. ak
  17. AnalogKid

    EEG circuit - need help please!

    It is a good notch filter circuit, but the example components are an extremely high impedance. You can scale everything by at least 100 to get normal parts and a circuit impedance less prone to picking up radiated noise. Keep in mind that the higher the circuit Q, the more distorted the output...
  18. AnalogKid

    EEG circuit - need help please!

    No. These type of filters rely on an input signal with a very low output impedance, which in turn is determined by the type of circuit, the type of opamp, and how much gain-bandwidth it has left over the feedback loop gain. Your frequencies of interest are so low that just about anything will...
  19. AnalogKid

    Remote Battery Issue

    Operation of the inside door locks does not depend on the remote. If they don't work, then maybe your remote is ok and there is something wrong inside the car. ak
  20. AnalogKid

    EEG circuit - need help please!

    The #1 reason filters do not work as well as predicted is because the R and C components are not the theoretically-perfect values. This is WAY easier to achieve when the values are not impossible to buy. Since you need signal gain anyway, I recommend changing the first two filters to the...
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