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  1. BobK

    lm386 and electret microphone problem

    I agree, it is not enough to drive anywhere near max output. A 1 transistor preamp (gain 10) would do it. Typically, the electret mic will have a sensitivity of -46dB at 94dBA in. The gain is 46dB (200) so you would get 1V out at that level. A normal voice at 1 ft is 70dBA, at 3in it would...
  2. BobK

    lm386 and electret microphone problem

    LM386 is a power amp. Bob
  3. BobK

    How to load sounds into a microcontroller

    Good_JokR, How much do you think it would cost you to build a car that rivals a Honda Civic in performance, reliability, aesthetics, etc.? Do you think it would cost you the same amount as it does for Honda to build one? Bob
  4. BobK

    4xLCD torches in series without using 4 lots of 3xAAA's

    I really was curious. Here is what you said: This does not mention using something fluorescent to determine the brightness. If implies you could see the brightness with your eyes. And putting them inside a computer case still seems strange to me. What is it lighting up inside your computer...
  5. BobK

    Using external xtal osc with a PIC

    The best place to look for these in in the include file for the processor found at: "Program Files (x86)\Microchip\MPASM suite"\p12f629.inc" You will see this line: _FOSC_EC EQU H'3FFB' ; EC: I/O function on GP4/OSC2/CLKOUT pin, CLKIN on GP5/OSC1/CLKIN
  6. BobK

    How to load sounds into a microcontroller

    Best bet would be surface mount, of course. We also need an amplifier of some kind. probably a MOSFET half bridge used with PWM output from the micro. Bob
  7. BobK

    How to load sounds into a microcontroller

    Remember, this thing has to go in a wrist watch, so I think most Arduinos are out. Bob
  8. BobK

    4xLCD torches in series without using 4 lots of 3xAAA's

    I am curious as to how you determined that your UV LEDs are bright. Do you have UV vision? If they are truly UV LEDs, you should not see them at all, or maybe a faint violet glow. If they appear bright, I suspect that they are not UV LEDs. I am also curious as to why you would place UV LEDs...
  9. BobK

    12V Battery on a 230V/50Hz Pump

    An inverter generally takes a low DC voltage 12 to 48 and steps it up to line voltage 120 or 230. Bob
  10. BobK

    How to load sounds into a microcontroller

    A microcontroller is not going to be cheaper. You need a programmer, and you would need to learn a lot. And to have even a few seconds of playback, you would need a microcontroller at the high end for memory, or an external flash chip to store the sound. I would guess that you will have $50...
  11. BobK

    Generator protection

    Okay, but a switch that guarantees both cannot be connected is safer. Bob
  12. BobK

    How to load sounds into a microcontroller

    A microcontroller might not be the best choice for you. You can buy sound record / playback modules that are small and cheap. Ever seen a talking greeting card? Bob
  13. BobK

    Generator protection

    Just to reiterate a point made by Grd3, that you have not commented on. You MUST NOT connect the generator to the house power while the house is still connected to the grid, for multiple reasons. 1. You will be powering your neighbors houses as well, which will cause an overload. 2. If...
  14. BobK

    DC MOTOR QUESTION

    The test I proposed in my only post was intended to determine if this was the case, as I suspected (one motor defective). Bob
  15. BobK

    DC Voltage Measurement to RS232

    You could get a data acquisition card or USB connected board which would be able to read analog voltages. The ±30V range would need to be scaled down most likely. Here is an example: http://www.dataq.com/data-acquisition/usb/?source=googlesda&gclid=CJOQyKvbtccCFVU6gQodagkNfQ A unit for just...
  16. BobK

    Obtaining maximum torque from a motor

    Well, motors are designed to run continuously, not provide a little twist and stop. This is not a good use for a motor. Why not use a lever arm and a weight to produce an accurate amount of torque? To get 150 Nm you could use 150 / 9.8 = 16.3 Kg on a 1m lever arm. If you absolutely must use...
  17. BobK

    Creating a 5.1 sound system

    Please clarify what you want to do. Do you want to build your own amplifiers? If yes, from discrete components, ICs, or modules? How much power? And, do you want to build the speakers as well? Bob
  18. BobK

    Parallel power supplies?

    Diodes are not good for current sharing. They will work fine if the voltage is equal, but a small voltage difference will cause a large current difference due to the exponential I/V curve. Resistors work better. I would go with Steve's diode (to prevent reverse current) + resistors...
  19. BobK

    12V Battery on a 230V/50Hz Pump

    Mine is 1300 gallons. The pump is 500W, and pumps 3500 GPH. It would take 41A at 12V, which is a bit much. Bob
  20. BobK

    Have you seen one of these and how can I make it work.

    To use it you would put the test leads into the R or C banana jacks and you would select a resistance or capacitance value via the rotary switches and the range switch (top left) for the R. The other switch allows you to select R and C in series, parallel or separate. When used in series, you...
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