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  1. BobK

    Inverter ... Mr. Gary Lecomte

    If you are just going to put a 60Hz sine wave thorugh a transformer it is going to be large to get 1000 Watts. The other option is to use a much higher frequency to step up the voltage and make a PWM based inverter on the output side. The higher freqency allow yous to use smaller inductors /...
  2. BobK

    Inverter idea - would it work?

    For any real power, you do not want to feed a sine wave to the transformer. The transistors will be operating in the linear region and thus heat up considerably. Inverters either use a modified sine wave (google) or use PWM to approximate the sine wave while having the transistors always...
  3. BobK

    1104 led rectangular array

    That was years ago! Bob
  4. BobK

    Need to turn small current into burst power

    Sorry, I made the mistake of not reading all the previous posts carefully before my answer. I see now that the battery can provide 6.8ma at 2.7V in pulsed mode. This should be more than sufficient to charge a capacitor for your 20ma bursts. You can size the capacitor based on the voltage...
  5. BobK

    Inverter ... Mr. Gary Lecomte

    Transformers are rated in Amps, not Amp Hours. Assuming you mean you are using a transformer that has a 12V 15A primary in an inverter, that is only 180 Watts. You cannot produce 1000 to 2000 Watts with such a small transformer. You would need at 1000 / 12 = 83 Amps to produce a 1000 Watt...
  6. BobK

    Audio transmitter

    88 to 108 MHz is the FM band. This is not all radio frequencies. Your initial post sounded like you wanted a means of transmitting audio that did not use ANY radio frequencies. Of course you can use frequencies outside the FM band. Amateur radio uses various other bands, for instance. Bob
  7. BobK

    Audio transmitter

    Infrared would be an option, but you have to have line of sight between the transmitter and receiver. Bob
  8. BobK

    Add two voltages without the use of a OPAMP

    Smokstack Urban Barbecue. Downtown. It is pretty decent, has live music, but as someone who once lived in Austin, I've seen better of both. BTW: one of my favorite restaurants is the Student Prince in Springfield. Bob
  9. BobK

    LED flash lite: Max Current vs forward voltage (dropping)

    Of course the light output increases, but the efficiency does not, it tends to decrease with increasing current. Efficiency = light output / power input. Power input = Current * Voltage The Voltage goes up with higher current, so, even if the light output goes up linearly with the...
  10. BobK

    LED flash lite: Max Current vs forward voltage (dropping)

    It will look half as bright, try it. Why do say no one has done it? I and many others have. This is how you control the brightness of LEDs, by keeping the current the same and varying the duty-cycle. You can also make a 3-color LED look like any color by varying the duty-cyles of the R G...
  11. BobK

    Add two voltages without the use of a OPAMP

    I have yet to see an opamp that needs dual supplies. If you check pretty much any opamp it will have a V+ and a V- input. Where is the ground input? So you can power an opamp from a single supply. The problem is getting the correct reference voltage (which is usually ground in a dual supply...
  12. BobK

    Need to turn small current into burst power

    Sorry, what yoiu ask is impossible. .25ma * 1sec = 0.25 ma sec 20ma * 20mSec = 0.4 ma sec The battery cannot provide the energy needed. That said, what kind of a battery can only put out .25ma? Bob
  13. BobK

    cartridge heater and pot problem

    If the heater draws 7.1 A at 120 V it has a reistance calculated by: V = I * R 120 = 7.1 * R 120 / 7.1 = R = 16.9 Ohms. If you connect this in series with a 250 R pot, with it set as the max resistance you will have a series circuit with 266.9 Ohms. So the current drawn is: V = I *...
  14. BobK

    How can i create an accurate thermometer using an LCD on Circuit Wizard

    One byte for integer part, one byte for fractional part. Bob
  15. BobK

    1104 led rectangular array

    I don't understand this comment. How does the source of the light affect whether or not it is able to penetrate the canopy? Photons are photons, are they not? Bob
  16. BobK

    1104 led rectangular array

    I would not take Gonzo's word for that, I would do a little more research. There is certainly no theoreitical reason why LEDs could not be used to make a good grow light. They are now among the most efficient light sources and offer good control over the spectrum produced. I do not know...
  17. BobK

    How can i create an accurate thermometer using an LCD on Circuit Wizard

    Google fixed point arithmetic. Bob
  18. BobK

    Treble booster

    http://lmgtfy.com/?q=RC+filter+calculator
  19. BobK

    LED flash lite: Max Current vs forward voltage (dropping)

    Also, LEDs produce less light per Watt at their max current than they do at a somewhat lower current, so boosting the current above the max and running a lower duty cyble will allow you to run more current but will not boost the efficient to achieve the same brightness. Bob
  20. BobK

    LED flash lite: Max Current vs forward voltage (dropping)

    You seem to think that you will save energy by flashing the LED. This is not the case. The eye is an integrating device, so if you power an LED 1/2 the time it appears exactly the same as if it is producing half the light, In fact, this is how you dim an LED. There is no benefit to operating...
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