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  1. BobK

    1 volt signal

    Assuming the 24V supply is coming from a transformer and it is not already connected to ground, you can connect the - side of it to ground. Bob
  2. BobK

    Driving an Ultrasound Transducer

    Yep, should be Zt = Thanks for catching that, I have fixed the original post. Bob
  3. BobK

    Driving an Ultrasound Transducer

    As Steve said, the resistance is not useful. You need to measure the impedance at 1.5MHz. You can do this by connecting your signal generatator thorugh a resistor and then measuring the voltage across the transducer. The resistor and the impedance of the transducer then form a voltage divider...
  4. BobK

    10 watt LED

    Did you try measuring the current? You have probably been over driving it and thus reduced it life time. If you read the description, it says you need a constant current driver for this, which is a good idea. Bob
  5. BobK

    DC and Low Pass Filters

    The magic comment was intended as humor after I had just explained how you can get a pure AC signal from a DC source. The OP was having trouble with that concept. Bob
  6. BobK

    Driving an Ultrasound Transducer

    Voltage is not the only thing that determines the power output. The LM318 can only output about 20ma of current. At 21V p-p (about 15V rms) this corresponds to an impedance of 600 Ohms for the transducer. If it's impedance is less than that you the opamp is being overloaded. Bob
  7. BobK

    Electric Grill

    The real question is why did you buy a 220V appliance when your mains are 120V? Bob
  8. BobK

    ICM7556 Monostable Touch Switch doesnt work

    The trigger input should be pulled high via a 10K or so resistor. Otherwise it is floating when you don't ground it. Bob
  9. BobK

    DC and Low Pass Filters

    When the output is high, The capacitor is charging as current goes thorugh the speaker to ground. When the output turns low, the side of the capacitor that is connected to the speaker has become negative and the thus the voltage on the speaker is negative and the capacitor discharges through...
  10. BobK

    LED Help!

    Use a string of shift registers such as the 74HC595. Shift in a 1 bit every second, then clear them all at the minute. They have 8 bits per package so you would need 8 of them. Bob
  11. BobK

    DC and Low Pass Filters

    A buzzer, fed a pure AC signal, would act like a very poor speaker, reproducing the frequency of the signal. But a 0 to 10V square wave is not a pure AC signal, as I have said twice before, it is a signal containing both and AC and a DC component. In this case the average voltage might be...
  12. BobK

    DC and Low Pass Filters

    Let me try once more. A square wave is not DC. DC is a constant voltage. A square wave is a changing voltage. A changing voltage is AC, possibly with a DC component. A square wave consists of many sine waves. One at the fundamental frequency of the square wave, and at all odd multiples...
  13. BobK

    C programming on PIC16F877A

    Hey Vic, You seem to be progressing rapidly. Congratulations! Bob
  14. BobK

    PIC development board

    Not necessary. I have run PICs on solderless breadboards, various prototype boards as well as PC boards all without a ground plane and they run just fine. Bob
  15. BobK

    DC Current Booster

    What you need is a switch mode regulator. They can reduce voltage with about 80 to 90% efficiency. If you want to know the theoy, look up buck converter. Bob
  16. BobK

    PIC development board

    The PIC microcontrollers do not have current limiiting, you must use resistors. Bob
  17. BobK

    DC and Low Pass Filters

    A square wave going from 0 to 10V for example, is not DC. It is AC with a DC offset of 5V. Bob
  18. BobK

    Fast Counter Design

    I don't know anything about AVR but, for the low end PICs the acqusition time is about 20uS, so a single pulse cannot fully charge the capacitor, which is why I reccommeded a long charge time over many pulses. If there was zero leakage in the diode or hold capacitor circuit, the cap would...
  19. BobK

    Basic random generator

    Are you talking about a true random number generator or a pseudo random number generator, they are two entirely different things. Bob
  20. BobK

    Solar cell, photoresistor and motor -- need help

    Duplicate. Do not post the same question in 2 places, because then people reading one have not seen what others have said on the other thread. https://www.electronicspoint.com/solar-cell-photoresistor-and-motor-connected-series-need-help-purchasing-parts-t243839.html Bob
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