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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

  2. audioguru2

    Some kind of RPM counter

  3. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Neo, You were smart to use opamps rated for a 44V supply. ;D The original opamps are rated for a max 36V supply but operate at 41V in the original project. Mixos, the owner of this site built the original project and him and others reported that it won't give 30V at 3A, has a lot of ripple...
  4. audioguru2

    Some kind of RPM counter

    Hi Marc, I have added a coupling capacitor from the phototransistor and a resistor to ground at the tach's input. The LM2917 won't operate from 5V so I have planned a 150 ohm resistor to feed its zener diode from 9V (not a 9V battery, its voltage drops too low) and some supply bypass caps.
  5. audioguru2

    Lamp contol with logic circuit

    Hi Circuity, Now that you have learned about the input currents of 74LS logic gates, you need to learn about the output currents. The output is guaranteed to be a logic high of 2.7V or more when driving a load resistance to ground of 6.8k or more. The max recommended output high current is only...
  6. audioguru2

    Lamp contol with logic circuit

    Most of your 10k resistors have two 74LS inputs, each with up to 0.4mA. Therefore the voltage across the 10k resistor is 2 x 0.4mA x 10k= way too high! If you use a 1k resistor then two inputs with a 1k resistor will be at 2 x 0.4mA x 1k= 0.8V which is the threshold voltage of a logic low and...
  7. audioguru2

    veronica fm transmitter

    In Google, enter Silicon Chip Micromitter in the search bar. the 1st link will be their crystal-controlled stereo FM transmitter project that is modern and works very well.
  8. audioguru2

    Lamp contol with logic circuit

    A resistor can be used to "pull-down" the input of a TTL logic gate. Each input when a few are in parallel needs 0.4mA at about 0.4V for a 74LSxx input, which is 1k ohm. An ordinary 74xx input needs 1.6mA at about 0.4V which is 250 ohms.
  9. audioguru2

    ISD2548

    When recording, anything that was previously recorded is erased. You can erase everything by recording silence.
  10. audioguru2

    ELECTRONIC NEGATIVE WAVE SILENCER

    Noise-cancelling headphones "reduce" noises, they don't completely cancel them. It works only at lower audio frequencies where the wavelengths are long enough so that the cancelling wave has the opposite phase of the original wave. If you use a speaker instead of headphones then it will be...
  11. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Hi Logan, The CD4069 linear amplifier has been documented as a high gain amplifier when it has a low supply voltage and was easily tested by me. I have never seen a test of a CD4049 inverter that is used as a linear amp and I have never seen one. Why don't you set-up, test and document the gain...
  12. audioguru2

    veronica fm transmitter

    The frequency stability of the Veronca transmitter was tested in a review in Google's cache. It drifted very much when its supply voltage was changed and when something changed its antenna. Its frequency stability was said to be not good enough for it to be legally used in Britain.
  13. audioguru2

    Lamp contol with logic circuit

    Hi Circuity, Your inputs are always high. Nothing in your circuit makes an input a logic low! Learn about the inputs of TTL logic ICs that are at a logic high unless something pulls them to a low.
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Manfred, You can make this power supply any way you want. I improved it so it can meet its spec's and be reliable without burning up. It is a good idea to use your surplus transformer and switch its secondary voltage to reduce heating in the output transistors. We should go over the details...
  15. audioguru2

    current and voltage op-amp

  16. audioguru2

    about mixer

    What do you need to know about this circuit?
  17. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Hi Logan, We have posted two articles about using Cmos inverters as linear amps. I just looked at Bandpass Filter in Google and found an article with exactly the same bandpass filter ircuit as in the Whistle Responder. I think that the project would have the sharpness of the filter at random...
  18. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Congratulations, 91% is wonderful. ;D Are you going to fix this Whistle Responder project's problems and post a re-design of it that works?
  19. audioguru2

    Differential amp vs op-amp

  20. audioguru2

    Help On Another Transistor Question

    Its quiescent-point is when it rests without signal. Its DC conditions.
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