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  1. BobK

    Arduino + Audio Amplifier Board Help

    What is the output from the Arduino? It cannot produce audio directly. If it is PWM, you need a resistor from the pin and capacitor to ground to make a low pass filter. It should have a cutoff of about 4000 Hz for voice. Also use a coupling capacitor between the output of the RC filter and the...
  2. BobK

    Driving a piezo buzzer: resultant tone is noisy. Why?

    If you drive it with a sine wave, it will not ring like that, but the output will be about 1/8 as high as it would be at the design frequency of 3700 Hz. Bob
  3. BobK

    Driving a piezo buzzer: resultant tone is noisy. Why?

    The buzzer is rated for 3700 Hz and probably has a strong resonance at that frequency. Your square wave input at 800 Hz is ringing this resonance. Looking at your waveform, assuming the lower frequency is 800 Hz, it looks like about 4.5 cycles of ringing which comes to 3600 Hz. Bob
  4. BobK

    How to find the circuit output

    Think about what happens when the input voltage goes to -12V, with and without the diode. Bob [mod edited to remove comments about AG's post that has now been removed Thanks Bob :) ]
  5. BobK

    PIC16F1939 High to low edge detection

    If the input is between Vil and Vih it is undefined, it is neither high nor low. So the amswer is no. If the input goes from above 1.5V to 0.9V it may or may not detect a high to low transition. It must go below 0.45V to ensure that it sees a transition. Bob
  6. BobK

    Career guidance advice please

    I would say the question comes down to: Would you rather do repair work or design work? Bob
  7. BobK

    elvi motor help

    How about a picture? Bob
  8. BobK

    How to build an IR-sensor from scratch?

    Hmm. I have used standard 38KHz TSOP detectors and I practically had to cover the emitter at the source make it fail, You could point the thing anywhere, from anywhere in the room as long as there was a reflective path to the detector and it would be detected. Are you sure you have the...
  9. BobK

    PIC16F1939 High to low edge detection

    To guarantee that it be recognized, yes. Something a little outside of that range might be recognized, but you cannot rely on it. Bob
  10. BobK

    Non-inverting audio Op-Amp

    Gains are multplied. If you have a gain of 3, and need 20db less, you multiply 3 by 0.1 to get a gain of 0.3. You cannot get a gain of less than 1 with that configuration. You can get a gain of 0.3 with a voltage dovider or an inverting amplifier. Bob
  11. BobK

    How do I wire a BMP085 Barometric Pressure Sensor?

    A breakout board typically just brings out the pins in a more hobbyist friendly form (like DIL). The datasheet should tell you all you need. Bob
  12. BobK

    Building an LED lamp with varying color and brightness

    Is this really what you meant? Bob
  13. BobK

    Non-inverting audio Op-Amp

    Nope, factor of 10 in voltage, 100 in power. You post is not clear, you say you want to "reduce the gain" but you have not told us what the gain is. Duke assumed you meant you want of gain of -20 db or 0.1. Is this correct? If you plug 0.1 into the gain formula you will find that you need a...
  14. BobK

    Total Electronics Novice In Need Of Power Supply Advice

    Do make sure the polarity is correct before plugging it in. Bob
  15. BobK

    Short/open circuit detector in wall

    At least here in the US, multiple outlets are strung together from the fuse box. If one outlet is out, it could be an open at another outlet in the same string. Bob
  16. BobK

    Using transistors

    The circuit you show is called an emitter follower. In that circuit, the voltage at the emitter is approximately the voltage at the base minus 0.7V. Which is, in this case, 0V. So no (or very little current flows). The small current that flows is the amount needed to drop the voltage across...
  17. BobK

    1/4 inch mono jack 3 pins

    I think the thread has be hi-jacked. Bob
  18. BobK

    1/4 inch mono jack 3 pins

    I cannot make sense of your tests. I don't see how inserting a stereo plug could short more of the pins together than inserting a mono plug. When you insert a mono plug, it sounds like it is a switched plug that shorts the extra pin to ground when a plug is inserted, But inserting a stereo...
  19. BobK

    PIC16F1939 High to low edge detection

    I don't think the pins are configurable as Schmitt trigger or not, this is pre-determined for each pin. The datasheet should tell you which type of input the specific pin you are using has. Bob
  20. BobK

    PIC16F1939 High to low edge detection

    I did not look at the datasheet, but, assuming you quoted it correctly, your calculations look right. Bob
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