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  1. AnalogKid

    Nixie Tube Driver Question (w/ Schematic)

    In #9, be sure to put a fixed resistor in series with the pot, so the current through the tube is not fatal when the pot is turned all the way to the left. The circuit in #7 will regulate much better than the one in #8 because of #7's large amount of negative feedback, versus none in #8 Also...
  2. AnalogKid

    Nixie Tube Driver Question (w/ Schematic)

    I'm not a big fan of shunt regulators, and this one is gonna dissipate a lot of unnecessary heat. If you don't like the simple 1-resistor current limiter, replace it with a 2-transistor constant current source. Then, all of the segment drivers can be emitter-grounded saturated switches with...
  3. AnalogKid

    Series Resistor in Place of Line Distribution Transformer

    It can if you are careful. Try this - Most people are familiar with a home stereo power amplifier. This is an almost pure voltage source, and has a very low output impedance, almost equal to a theoretically perfect 0 ohms. It is so far removed from the vacuum tube amplifiers that were the...
  4. AnalogKid

    With a Little Help from my friends?

    If getting the RF circuits to work isn't working, an alternative is a Theramin based on optical, rather than RF sensing. Two photo-resistive cells, one varies the gain of an amplifier and the other varies the frequency of an oscillator. You wave you hands over the cells to block out variable...
  5. AnalogKid

    Voltage threshold issue

    Manufacturing margin: The voltage/current/resistance range over which a pin is guaranteed to function, and the range over which it actually will function, are two different things. ak
  6. AnalogKid

    resistor confussion

    No. 0.02 A Watt's Law: P = E x I >> Power equals voltage times current. ak
  7. AnalogKid

    Build pwerbank ?

    To me, charging a 5 A-h battery in 2 hours means it has to be a lithium battery pack. Charging one that big that fast is just plain dangerous. To be clear - I know exactly how to do this and have most of the parts, and I would not do this. Buy one from a reputable company, not...
  8. AnalogKid

    series or parallel?

    That's two in one week. You're on a roll - !!! ak
  9. AnalogKid

    series or parallel?

    Parallel - only parallel - no exception The motors will not have the exact same impedances, so in a series string they will not all see the same driving voltage. Also, the motor design assumes a low impedance power source. Thus, wiring them in series will not deliver consistent performance...
  10. AnalogKid

    Complete beginner help with finishing linear DC supply

    Nothing. A diode and capacitor form a peak detector. The transformer output has a low impedance, so it charges the cap about as fast as it rises. When the input is on the downside of the sinewave and there is nothing connected to the cap to discharge it, it holds the peak voltage and the...
  11. AnalogKid

    Complete beginner help with finishing linear DC supply

    Meds - ?
  12. AnalogKid

    Complete beginner help with finishing linear DC supply

    Depends on what your goal is. For signal circuit testing, the transformer you have is way overpowered, but that's not automatically a bad thing. There are several ways to limit the max current a power supply can deliver to a circuit, so you can throttle back the current to something like 500...
  13. AnalogKid

    Does the antenna only increase transmitting range or can it increase reception in regards to flipper zero and the CC1101 Wireless Module?

    The link requires registration.
  14. AnalogKid

    Short term battery backup circuit

    A common interaction with people who are new to this is to convince them that a schematic, no matter how bad it looks or how incomplete it is, is a critical part of just about every *question*, not just the solution. In fact, I have a packaged response for it. Paraphrasing Rear Admiral Joshua...
  15. AnalogKid

    Short term battery backup circuit

    Here is #17 reworked for using the car battery as the holdup power source. I adjusted the values of some components, but without real information about the device being powered they all are guesswork. Did you know back in post #1 that the car battery would be the backup energy source? ak
  16. AnalogKid

    Short term battery backup circuit

    Here is the updated schematic from post #11. R3 and R5 are added to assure that the transistors turn off completely. Note again that some of the component values will change when more is known about the device being powered, the size of the battery, etc. Note also that no lithium battery of...
  17. AnalogKid

    Short term battery backup circuit

    Here is a minimalist concept of a short-term backup with automatic switching. An operating assumption for these numbers is that the 12 V device will operate down to 10 V. R1 limits the peak charging current to something that won't disturb other devices in the vehicle. D1 is beefed up for the...
  18. AnalogKid

    Short term battery backup circuit

    The link brings up a page that requires registration. Also, depending on the current required by the radio, there might be a much more simple way. Basically, it is a version of what is going on with the energy supply to the Q1 base. As mentioned in #12 - if the device current is low, such as...
  19. AnalogKid

    Short term battery backup circuit

    The schematic in #11 is missing one or two resistors. Is there any way to update that post, or do I have to create another post. None of the other fora I'm on have a fixed time period for updates and corrections. Also - if the device current is low enough, B1 could be replaced by a large...
  20. AnalogKid

    Short term battery backup circuit

    Here is a first pass at a *concept* schematic. Most of the components have to be adjusted to fit the actual device parameters. R2 trickle-charges the backup battery whenever the engine is running. D1 disconnects the vehicle electrical system when ignition is off, so those devices do not drain...
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