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  1. AnalogKid

    USB power for tablet and a USB hub

    Red is +5, black is GND. There is no 12V being distributed in the drawing. Grey and green are the USB signal pair. Inside a car the cable distances are so short that I don't see a problem here. ak
  2. AnalogKid

    Purpose in syncronizing electronic signals

    "forget the power supply" makes your question even harder to understand. There are hundreds of different general reasons for a system to require that some or all of the internal or external signals be synchronized, and millions of specific reasons. If you are talking about a power supply with...
  3. AnalogKid

    Splitting voltage

    Welcome to high school physics. Today's topic is the cosine of gravity...
  4. AnalogKid

    Splitting voltage

    Now you're getting there. Engineers working with data conversion talk about ENOB - effective number of bits. As above, in round numbers: 0.1% is effectively 10 bits. 0.2% = 9 bits 1% = 7 bits 2% = 6 bits So a voltage divider made with 1% resistors turns your 10 bit A/D into a 7 bit A/D in...
  5. AnalogKid

    Splitting voltage

    Your theory is clear, but will not work in the real world. The worlds most perfect 10 bit A/D converter has a resolution of 1 part in 1024, or almost exactly 0.1% accuracy. If your voltage dividers use 0.000001% accurate resistors, and you take the two readings and combine the results, the...
  6. AnalogKid

    Splitting voltage

    Everything you describe can be done with 3-terminal regulators. These function as electronically controlled variable resistors to maintain a constant output voltage when the input voltage or output current vary. An example would be the LM7805, which can take anything from +8V to +25V input and...
  7. AnalogKid

    Exactly how evil are Capacitors?

    The glasses are part of a forum software feature that does not work well. Whenever you reply to anything, this forum automatically assigns "watched" status to he thread. In theory, you will get an alert whenever anyone posts things to the thread. This can be handy if you are participating in...
  8. AnalogKid

    BJT Output Stage

    What is the load being switched. Also, what is your question? Does the circuit not work as intended? If so, in what way? ak
  9. AnalogKid

    I need to turn on an LED when switch is open

    There are magnetic alarm switches available that have both normally open (form A) and normally closed (form C) contacts, like a SPDT switch. Under $3 with free shipping. One of those in series with the LED and its resistor will work...
  10. AnalogKid

    Electronic timer motor

    Motor voltage motor current power supply for the timer circuit location - indoors, outdoors, packaged for an office, open frame for a basement, etc. your skill set - access to components, soldering, etc. ak
  11. AnalogKid

    DIY Guitar Pedal, not functioning at all, advice please.

    Note that while this schematic has two separate symmetrical diode clippers toward the output, the 1-transistor overdrive part probably is asymmetrical. That is, unless the transistor operating point bias is perfectly centered (difficult to do with dangle-biasing), one polarity of audio the...
  12. AnalogKid

    DIY Guitar Pedal, not functioning at all, advice please.

    There is nothing explicitly incorrect in the schematic, so zero output = wiring error. ak
  13. AnalogKid

    Sawtooth oscillator

    That is not a saw wave generator. It is an integrator. With a DC level for an input it produces an inverted ramp. Positive input equals negative-going ramp, and vice-versa. Ignoring the control input for a moment, if you put it in series with a comparator in a loop, so the ramp output drives...
  14. AnalogKid

    I need a PCB designed

    For the schematic in post #25, the Arduino can drive Q2 directly without R2 or D2. Increase R4 to 10K to reduce unnecessary power loss. If you want the MOSFET to source current at +12V rather than sink current from a +12V load, then you need a P-channel MOSFET as the power switch and an...
  15. AnalogKid

    120v dc power supply

    OK.... I might be confusing different rule sets from different fora. ak
  16. AnalogKid

    Battery monitor indicator ??

    Is that good enough? ak
  17. AnalogKid

    Ceramic resistor information

    One that size is rated for at least 100 W steady state dissipation. ak
  18. AnalogKid

    Hot-swap dual battery setup.

    Actually, the efficiency of the circuit in terms of circuit power consumption or loss relative to the energy delivered to the load is almost completely dependent on the switching devices, not the amount of control goop behind them. With one power MOSFET for each battery, the power system...
  19. AnalogKid

    Building a portable solar charger for my laptop!!

    Since the laptop has internal batteries, what is the purpose of the external SLA battery? Your overall plan should work fine. ebay has many low cost boost converter modules. ak
  20. AnalogKid

    Convert DC to AC

    As you look at the schematics, you'll see that many are a variation on one theme - a centertapped primary with the tap connected to the + DC source, and two power transistors driven out of phase pulling each end of the primary to ground. This produces either a squarewave or modified squarewave...
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