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  1. C

    Walmart power adapter voltage increase if in-between two settings?

    The circuit has been incorrectly designed and the voltage rises to full output voltage when the switch is not making contact. If the switch wiggles when it is in the wall, your equipment will be damaged.
  2. C

    Good Soldering Station

    "no thanks too cheap sounding" What a stupid, ignorant, thing to say. I had Weller irons 50 years ago. They are rubbish. Look at a previous thread about Weller irons and all the problems.
  3. C

    Good Soldering Station

    Either a soldering station or an adjustable iron for $12.00
  4. C

    DIY Resistance Box

    I bought a resistor substitution box 50 years ago.I have never used it.
  5. C

    Explain me how to make an "Electromagnet Solenoid" more powerfull

    You cannot do anything other than increase the voltage.
  6. C

    Driver Circuit Components

    "when pin1 of the comparator equals to 9.4volt (high time), the divider will provide 2.2*9.4/(2.2+5) = 2.87volt to the base of TR2. However, the base of TR2 requires only about 0.7 volts when it turns on." No. That's not the way to consider it. Remove R8. R7 will deliver about 2mA to the base...
  7. C

    Stepper Motor Max RPM

    This is the most important part of the article: So the Theoretical maximum RPM for the Stepper using a 36V Power Supply AND reaching the rated current of 3.5A is only 580 RPM.....I am NOT saying a 36V supply will not spin one of these motors faster than 580RPM, but the torque will drop-off very...
  8. C

    Apple vs the FBI

    The whole point is this. Once thy get the crack, and use it once, they say they will destroy it. This will not happen. Already every state in the US has hundreds of phones that need cracking for court cases. Already personal documents held by the government have been leaked "Wiki-Leaks" and...
  9. C

    Driver Circuit Components

    This is a simple linear voltage regulator for -9.4V output voltage (V(ZD1)-Vbe(TR1)). should be This is a simple linear voltage regulator for +9.4V output voltage (V(ZD1)-Vbe(TR1)). C3/R11 indeed form a a low pass filter The more-accurate definition is: R11 provides base current for the...
  10. C

    Apple vs the FBI

    It just shows how incompetent the FBI is.
  11. C

    Transistor hfe

    R7 should be a value to prevent the transistors turning on when the quiescent current for the 7812 flows.
  12. C

    Transistor hfe

    " That is very confusing, as there's a big margin between 100 ohms and 0 ohms !" No. 100 ohms and infinitely high resistance. 0.871mA ?????????????? A value of 0.1 ohms 10W power resistor 5 amps through 0.1R will produce 500mV. This is simply an adjustment voltage to make each...
  13. C

    Transistor hfe

    Do not eliminate R7. The 7812 can get its quiescent current from the base of the transistors. You don't need R7.
  14. C

    Transistor hfe

    "ballast resistors" They are not ballast resistors. They are BALANCING RESISTORS or EQUALISING RESISTORS. Get your terms right.
  15. C

    Good electronics parts online sites?

    No-one is cheaper than eBay
  16. C

    AC 0-20A Analog Panel Meter for use with house hold 120V / AC

    And you will need a bridge.
  17. C

    Trickle Charge Batteries

    But you haven't told him what input voltage he needs.
  18. C

    Transistor hfe

    Remove R7. It is not needed.
  19. C

    Transistor hfe

    Normally you "drive" a transistor. In this case the transistor "takes" or "allows to flow" the necessary base current to deliver the collector current. At 5 amps and a gain of 1,000 the base current will be a few milliamp.
  20. C

    electronic speed control for drill motor

    A Universal motor has a wound field so the motor will operate on AC or DC. It is also a high RPM motor, such as in a Vacuum Cleaner. A motor in a power drill is a 3-pole motor. To reduce the speed you need a PWM circuit capable of handling about 30 amps. It all depends on the wattage of the...
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