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  1. (*steve*)

    Current sensing circuit help

    imagine a transformer with n primary turns and m secondary turns. If you have an AC voltage v at the primary, the secondary voltage is v x m/n. if you have an AC current i at the primary the secondary current is i x n/m. So, to achieve more sensitivity in a current transformer the ratio n:m...
  2. (*steve*)

    Capacitor Protection Boards- How do they work?

    As stated above, the original circuit: Could probably be changed to: it's interesting that the R2 is 100k as opposed to 180k in the other circuit. edit: looking closely, R2 is 180k in the original circuit. It was a bit hard to read from the photo, but with a closer look... (and it has...
  3. (*steve*)

    Current sensing circuit help

    You need to make it more sensitive. A current transformer with a lower turns ratio would be a good start.
  4. (*steve*)

    Pnp bjt

    It is a transistor with inbuilt resistors as shown in his schematic. I'm not exactly sure why they call them "digital transistors", but they save 1 or 2 components when you want to drive a small load from a microcontroller pin. ROHM has more information (searched for by typing "what is a...
  5. (*steve*)

    Capacitor Protection Boards- How do they work?

    Obviously @Bhargav Makodia isn't going to put in the effort, but since I am somewhat curious, here is my first attempt: That's based on the positions on the board and the polarity determined by the only marked semiconductor (the 2SD1804). All the unmarked semiconductors are assumed to be...
  6. (*steve*)

    Easiest/cheapest way to prevent a capacitor from over charging??

    A TL431 has a much sharper knee than any low voltage zener. This can be used to turn on a transistor which will shunt away any excess current. These have been discussed quite a bit here previously, including reverse engineering a Chinese capacitor protection board. I'll try to find you a...
  7. (*steve*)

    Phone's car charger

    Did you change the 470uF capacitor?
  8. (*steve*)

    Voltage source and current source on source electrode of MOSFET?

    Maybe the MOSFET is drawn upside-down for a reason...
  9. (*steve*)

    Pnp bjt

    So, the circuit isn't relevant to the question? The emitter-base breakdown voltage is low compared to the collector-base breakdown voltage. This means that the transistor will break down at a much lower voltage. The base-collector junction is very different to the base-collector junction, so...
  10. (*steve*)

    Pnp bjt

    If there collector is shorted to ground, how has the collector voltage exceed any other voltage in the circuit?
  11. (*steve*)

    I dont know what is this component in my circuit

    Do you know what a TRIAC is? Do you know what an optocoupler is?
  12. (*steve*)

    I dont know what is this component in my circuit

    Do you know what a TRIAC is? Do you know what an optocoupler is? What experience do you have with safely working with mains voltages?
  13. (*steve*)

    I dont know what is this component in my circuit

    It's a lightbulb. However in the circuit it appears that the bulb is shorted out. Where did you get the circuit, and why are you contemplating building something that you clearly don't understand?
  14. (*steve*)

    Pnp bjt

    Vc of the pnp transistor should never exceed the emitter voltage. Is the load referenced to ground? You don't show that.
  15. (*steve*)

    AIWA-AV97HR volume control not working

    There are three (or 4) connections to the pot. One is the signal input (which will go to one end of the pot) Another is the attenuated signal that goes to the amplifier. The third connection is to the other end of the pot and is the common ground for the signal. If there are 4 connections...
  16. (*steve*)

    AIWA-AV97HR volume control not working

    Does it have a manual volume control? This symptom can be caused by the ground side of the volume pot going open circuit.
  17. (*steve*)

    impedance matching required at 20MHz?

    Yes
  18. (*steve*)

    Current sensing circuit help

    I recommend you read the datasheet. The simulation doesn't exactly match the real thing.
  19. (*steve*)

    Project idea

    How about a simple oscillator?
  20. (*steve*)

    Super capacitor phone battery

    In 5 to 10 years will we also see some sort of improvement in battery technology too?
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