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  1. C

    Running 3v and 9v at same time from 6 batteries

    The servo needs 5v and the relay needs a transistor.
  2. C

    need help with an amplifier

    "As I understand the task, the amplifier should work in the quasi-linear range with a gain of 100. Hence, the transistor is neither turned (switched) ON nor OFF." To start with, you are missing the whole point of my discussion. The output transistor will be fully turned ON. The base bias...
  3. C

    need help with an amplifier

    Here's a very simple way to work out the voltage you will get across the 32R load (32R speaker). The first thing you have to understand is this: The energy entering the speaker is not via the transistor but via the 220R load resistor. The output transistor merely turns ON and "empties" the 1u...
  4. C

    Help with 555 device and interfacing with another device

    You need a 330R resistor in series with the LED.
  5. C

    Scavenging MOT's for bench power supply use?

    You just wind them with tape and put a coke cola bottle over each lead. The outcome will be different if the output is loaded or not. You are just determining the worst outcome.
  6. C

    Issues with RF transmitter/receiver pair in DIY remote control car

    Use a separate supply for the motor and add a relay for the moment to see if the range improves.
  7. C

    Scavenging MOT's for bench power supply use?

    Connect it to the mains with open output and feel it after a period of time
  8. C

    Adjustable frequency PWM, need to further adjust frequency (HELP)

    See that little thing between the two big blue things. Change it to 473
  9. C

    About transformer?

    Two separate 18v windings allows you to connect them in parallel to get a higher current. When you connect them in parallel, you put a 10R resistor between the two red wires and if it burns out, the leads are connected around the wrong way. Do it again and if the resistor gets warm or hot, the...
  10. C

    Finding the smallest possible actuator, or a new solution. Help massively needed!

  11. C

    PLEASE HELP ID THIS!!

    1% absolutely certain.
  12. C

    PLEASE HELP ID THIS!!

    The alarm makes a sound when the item is is attached to, is moved.
  13. C

    PLEASE HELP ID THIS!!

    It's an alarm with a vibration detector
  14. C

    Fuzz Pedal, adding a fuzz pot?

  15. C

    A place to find modern equivalents of old components

    Try NTE
  16. C

    Can I connect 2 speakers together?

    Connect them in series.
  17. C

    Help with a simple receiver.

    "There is nothing wrong with the 4.7 uF capacitor. Leave it in the circuit as shown." Here is your answer: LOADING The whole success of picking up a radio station is the RECEIVING CIRCUIT. The receiving circuit is the coil and the signal in the air (from the radio station) must go down the...
  18. C

    Help with a simple receiver.

    In my circuit above, the front end is very lightly tapped by the ratio of the 60 turns to 7 turns of the two windings. Anything like 4u7 will completely kill the front end. It takes 2 stages to drive a piezo and 3 stages to drive a magnetic earpiece.
  19. C

    Help with a simple receiver.

    Here is an article on crystal sets: Crystal Set - The
  20. C

    Help with a simple receiver.

    It's such a bad design that you don't need to build it. The 4u7 is far too high a value. The headphone will need to be greater than 1k for the circuit to work.
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