Search results

Search Forums New Posts
  1. BobK

    buzzer amplify

    I guess the sound_play function is a library function? You will not be able to use it. You will have to manipulate the port bits directly. It looks like you are using RA2 as the output. If you make RA1 the other output, it would look like: (not sure of the syntax for your C compiler)...
  2. BobK

    buzzer amplify

    Okay. Right now, you presumably have one side of the transducer connected to ground and the other to a micro output pin. Then you toggle that pin between 1 and 0 to create a square wave. To get twice the voltage, connect each side to a micro output pin. The toggle the pins line this...
  3. BobK

    buzzer amplify

    You can double the voltage from the microprocessor by using 2 output pins in a bridge configuration. I.e. You switch from pin1 high, pin 2 low to pin 1 low, pin2 high. Bob
  4. BobK

    Using $1 stereo amp in mono mode

    If you are using the USB port on your computer to power the speaker it can only draw 100mA, which makes 0.5W. You computer may be able to deliver more than that, but there is no guarantee, and it might just shut down, or reduce the voltage. You would be better off to run it off a USB wall...
  5. BobK

    buzzer amplify

    It does give a resonant frequency of 3.6KHz. What frequency are you trying to send to it? It might be a lot louder at the resonant frequency. Bob
  6. BobK

    buzzer amplify

    Then it is not a piezo buzzer. It is a piezo transducer. Some of these will have a resonance frequency at which the sound will be maximized. You can also drive it with a higher voltage by using a transistor switch. Can you link to a datasheet for the one you have? Bob
  7. BobK

    buzzer amplify

    A piezo buzzer, if that is what you have, has an oscillator built in and makes a sound if you simply connect it to a battery. Using the highest voltage that it is rated for will give you the loudest sound. If you need louder, buy a buzzer that is louder. They normally come with a dB rating so...
  8. BobK

    Stage Line 500W amp repair project

    You could, but we already know what you should be measuring and what you measure and it indicates that the junction of R108 and the base of the transistor is shorted to the positive supply rail. Any measurements of the right channel would not tell us any more. Bob
  9. BobK

    Lm317 led current?

    Why not use the LM317 in it's constant current configuration? A 1K pot in series with a 62.5Ω resistor would allow control from 20mA down a 1.1mA. http://users.telenet.be/davshomepage/current-source.htm Bob
  10. BobK

    Stage Line 500W amp repair project

    I don't think so, it is well isolated by 100K resistors from the circuit in question. I don't remember where that link came from, was it to bypass the protection circuit? Bob
  11. BobK

    Problem with Interrupts - PIC18F1220

    The problem with a delay in an interrupt is that, eventually, you will have the main program doing other time critical things, and if there is a delay in the interrupt routine, all that will stop. For a more complex real-time system, you would use a timer interrupt that increments a variable...
  12. BobK

    Variable power supply for under 3 volts

    Yes, that is what he meant, and referencing the LM317 to that negative 1.25V supply will allow you to make a regulated voltage supply that goes all the way down to 0V. But I still say that a regulated voltage supply on the base of a transistor is NOT the way to do it. If you want a constant...
  13. BobK

    Stage Line 500W amp repair project

    Gee, thanks. I think I have actually identified the problem, but once again, you do not believe me. Good luck. Bob
  14. BobK

    Voltage from rotation

    If you really want to generate the maximum power, you should wind the coil on a ferromagnetic core that is a torus with a gap, and the magnet should pass through the gap as close as possible to the core. This will concentrate all the magnetic flux through the coil. Bob
  15. BobK

    Resistor value identification

    I think this confirms by original post of green brown gold = 5.1Ω It measures close enough to be a 10% tolerance resistor of that value. Edit: If it is indeed reading correctly, it remains to be determined why it was burning up, replacing it is not likely to help. Bob
  16. BobK

    Power banks in parallel to increase A / mAh

    If your two batteries are 5V 1000mAH, giving you 10V out at 2000mAH, and your buck converter goes back down to 5V, at 100% efficiency, it would be the equivalent of 2000mAH. Why? Because the buck converter from 10V to 5V have a 50% duty cycle drawing only the current needed by the load. On...
  17. BobK

    FSK project

    Good idea! I like it. You could have multiple receivers or a single receiver with multiple relays to control more than one device. Once you have demonstrated either of them the rest is just adding more of the same hardware. Are you up on microcontrollers? They would be the best way to...
  18. BobK

    Power banks in parallel to increase A / mAh

    Not true. A perfectly efficient buck converter would give you the sum of the capacities if you placed the batteries in series. A realistic one would give you 80% of the sum of the capacities. Bob
  19. BobK

    FSK project

    USB is an extremely complicated protocol. You would need to use a microcontroller that has USB support to do this. I think this is a little beyond the scope of your assignment. A better idea would be to transmit data that goes into a serial port on the computer. The digital data from the FSK...
  20. BobK

    Power banks in parallel to increase A / mAh

    That unit will consist of a LiIon battery (3.7V) and a boost converter to up it to 5V. Paralleling them would not work well. If you want more power, buy a larger capacity power pack. Bob
Top