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  1. AnalogKid

    Trouble making high pass filter

    Carrier current signalling has been around for a loooong time, although not at such low frequencies. Look into X-10 home automation components and FM intercoms for time-tested examples of how to transport digital and analog signals on an AC power line. A common aspect of both systems is a much...
  2. AnalogKid

    2 Diodes in Series

    1. The two diodes in series act as a zener diode to limit the peak voltage across the output. 2. This circuit can kill you. ak
  3. AnalogKid

    555 timers

    Actually, they were used in the original joystick *interface card*, not the joystick itself. And the card used a now obsolete quad-555 part. http://www.next.gr/circuits/PC-joystick-interface-l43692.html Where are you located? ak
  4. AnalogKid

    Trouble making high pass filter

    Your question needs a lot of work. What is it you are trying to do? Separate a multi-kHz signal from the AC powerline? Reduce coupled 60 Hz noise? Why is a transformer necessary? Why is the transformer part number a secret? 60 Hz to 1 kHz is roughly 4 octaves, so a single pole filter will...
  5. AnalogKid

    Need Help with Radio Shack Kit Project

    Your notes are hard to read, so this will go better if you ask specific questions here. To answer one question: No, polarity does not matter *in this circuit*. This circuit has no semiconductors (transistors and diodes), so current is free to flow in both directions. Note that "series" is...
  6. AnalogKid

    Royer oscillator How it works ?

    Most oscillators have no obvious start mechanism. they start up because components are not perfect. In the case of your schematic, the two halves of the transformer primary are not perfectly balanced, and the two MOSFETs do not have exactly identical transfer characteristics. The circuit...
  7. AnalogKid

    Timer Switch For Ride ON toy

    The max discharge current for a battery like that is around 10-12 A, so the circuit is the timer driving a 20 A logic level power MOSFET. Logic-level because a standard MOSFET likes around 10 V of gate "drive" (Vgs, the voltage from the gate to the source). 20 A because it always is best for...
  8. AnalogKid

    Timer Switch For Ride ON toy

    When the battery is powering the toy continuously, how long does one charge last? ak
  9. AnalogKid

    Timer Switch For Ride ON toy

    What power is available to the timer circuit? What is the max voltage and current the timer circuit has to control? For anything over 1 minute, I strongly prefer an oscillator/counter chip to a timer chip like the 555. It's the same body count (number of components), but the...
  10. AnalogKid

    Mystery box

    What are the part numbers on the TO-3 devices? What is printed on top of the transformer? ak
  11. AnalogKid

    What is this?

    It is a resonant transformer. The primary coil is tuned by one section of the tuning capacitor. The secondary coil drives the rf amp stage...
  12. AnalogKid

    What is this?

    That is the AM radio receiver antenna coil, also called a loopstick antenna. https://en.wikipedia.org/wiki/Ferrite_core https://en.wikipedia.org/wiki/Loop_antenna#Small_loop_receiving_antennas ak
  13. AnalogKid

    Problem with buffers and stepping down to low voltages

    The first case is 31 steps. The second case is 310 steps. One side of each switch goes to a wire that is not connected to anything. 1.5 mV probably is below the input offset voltage error range of the opamp, especially in a circuit with "infinitely" different inverting and non-inverting input...
  14. AnalogKid

    Substitute for MC14049 inverting hex buffer

    Exact same part. The CD part was first introduced by RCA when they developed CMOS for the market. When Motorola got into CMOS, they started all of their parts with MC - Motorola CMOS. Note that that is an old, early part, and is "unbuffered". Early CMOS parts were *extremely* sensitive to...
  15. AnalogKid

    Time delay for cheap.

    Depends on the solid state relay. Many that list a wide control voltage range have a small constant-current circuit in series with the optocoupler LED, so the input current is almost constant no matter what the input voltage. Best to test this theory with a series resistor, but if the...
  16. AnalogKid

    Time delay for cheap.

    10,000 uF / 25 V eC=it voltage drop times capacitance equals current times time 12 V supply - 3 V min operating voltage = 9 C = holdup capacitor in farads 3 mA operating current = 0.003 30 seconds = 30 9 x C = .003 x 30 C = 0.01 F = 10,000 uF ak
  17. AnalogKid

    Ring Doorbell

    Those are wire-wound. Depending on the construction, wire-wound resistors can be much more survivable with high transient currents, or intentionally blow like a fuse (the 'fusistor'). Hollow core vitreous enamel parts are very rugged. Note that when operated continuously at 50% or more of...
  18. AnalogKid

    Detecting a Signal of varing contant frequency

    On your schematic, the point labeled "Signal to Check" is actually connected to Ground. The signal you want to check is the R1-D1 node. Note that this signal will be only around 2 V because of the clipping action of the LED. As above, a missing pulse detector will do what you want. Many fan...
  19. AnalogKid

    I Want To Make A Device That Tells Me That Electricity Is Back

    When you go to generator power, do you use a manual changeover switch at the breaker box or does the generator do it automatically? Either way, you have to connect something to the power company AC feed to your home. A very simple circuit can notice when that AC power goes out, and then...
  20. AnalogKid

    Need help with a simple circuit

    Where are you located? Before we get to circuit design, let's do a little product design: How many LEDs, what are their colors, what are their functions? How do you restart the game if you bump the wire? What is the unlock mechanism. The circuit and 1 or 2 LEDs is a very low power device, but...
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