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  1. audioguru2

    Negative charge pump

    Good, now you have a working circuit. Can you get enough current out of it to supply an amplifier? When it is fully loaded by the amplifier, how low does its output voltage drop? What is its input current at full load? How much ripple on its output?
  2. audioguru2

    Neon flashes with the music

    Sure, just step-up the voltage with a transformer. A cheap, small audio transformer that has a 1K primary and an 8 ohm secondary will work if you connect the 1K terminals to the neon bulb (you may also need a current-limiting resisor in series with the bulb) and the 8 ohm terminals to the...
  3. audioguru2

    wireless transmitter

    Hi Hakyman, AM radios use a ferrite bar antenna that works pretty well at their low frequency. I don't see why it won't also work for transmitting.
  4. audioguru2

    UV exposure and white LEDs?

    Hi Kain, A white LED isn't the same as an RGB LED. Just read a datasheet. A white LED is really a blue one with a yellowish phosphor added. That is why they aren't very white. The light comes from a single location on the chip so it can be easily focussed. An RGB LED has 3 separate LED chips...
  5. audioguru2

    limiting rpm

    The RPM and power limiter of a gas engine is called its throttle. Just turn it down to go slower.
  6. audioguru2

    LM78XX & LM79XX questions

    Trigger, a 0.1uF cap has a value that is much too low to smooth mains ripple. The main filter cap will have a value of thousands of microfarads to do that. As the datasheet says, the 0.1uF cap at the regulator's output improves its transient response. Transients are abrupt, fast and high...
  7. audioguru2

    Newbie question about transistor Hfe

    Hi JRCFG, Hfe is for AC gain and hFE is for DC, I think. You can't calculate or measure hFE when the transistor is switched and saturated. What if the base current was equal to the collector current? Is its hFE only 1? Of course not! You can measure hFE when the transistor is linear, not...
  8. audioguru2

    LM78XX & LM79XX questions

    Hi Autir, You should use the capacitors recommended on the datasheet by the IC's expert designers. They know that a ceramic disk cap is much better at very high frequencies than an electrolytic cap, and that larger ceramic disks are also poorer. They recommend a 0.1uF ceramic disk output cap...
  9. audioguru2

    3V LED Chaser project

    Hi Guys, I just finished a 3V LED Chaser using orange low-voltage Ultra-bright LEDs. It is extremely bright on-axis (the LEDs have a 20 degree beam). I used the new 6V circuit with a few changes to allow it to operate with a supply of only 2V to 3V. My daughter leaves her chaser running all the...
  10. audioguru2

    3V LED Chaser project

    Hi Ibernez, All the ground points on the schematic should be joined together when you build it. The wire that you solder to the copper tape shield can be connected to any of those points. A 1M (1 Meg) audio taper (logarithmic) pot is commonly used as a volume control in audio equipment. If you...
  11. audioguru2

    LM78XX & LM79XX questions

    Hi Autir, 1) Self-oscillation occurs with some circuits like a regulator that have a very high gain and a lot of negative feedback because of phase-shifts in the circuit and load. 2) The output cap improves transient response because it absorbs sharp transients that the fairly slow regulator...
  12. audioguru2

    LM78XX & LM79XX questions

    Hi Autir, Here is what National Semi says about those caps:
  13. audioguru2

    3V LED Chaser project

    Hi Ibernez, Those very bright LEDs are perfect. Just hope that their voltage is close to the low end of their spec so the battery will last longer. Long ago, the "ground" connections of a radio were connected to a wire attached to a metal rod that was pushed deep into the earth. Today, the...
  14. audioguru2

    Dome Lamp Dimmer

    Hi Alun, I suppose that an incandescent lightbulb dims OK with PWM from 99% to 25% since when it is dimmed, more of the reduced power goes into making heat, not light. I was thinking about dimming Ultra-Bright LEDs with PWM where the LED is still glowing when the duty-cycle is 1000:1. Half the...
  15. audioguru2

    3V LED Chaser project

    Hi Ibernez, My orange LEDs are rated at 4000mcd brightness at 20mA and about a 20 degree total beam angle. They were about $5.00 for 10. If you don't connect the shield to the circuit's ground, it will pickup the interference by capacitive-coupling due to its closeness and re-radiate the...
  16. audioguru2

    Negative charge pump

    Hi Kevin, Your "fixes" to your circuit will cause big problems: 1) You have shorted the bases of the first transistors together so now the upper transistor cannot be an emitter-follower. Each transistor should have its own base resistor. 2) The diode that you added to the first transistor to...
  17. audioguru2

    What is Diac?

    Hi Suraj, If you use an ordinary transistor instead of a a Diac in an AC circuit it would not drive the Triac properly and would likely overheat. A Diac has equal threshold voltages for both polarities of the AC mains voltage. When the threshold voltage is reached across a Diac, it conducts...
  18. audioguru2

    3V LED Chaser project

    Hi Ibernez, The low-voltage orange Ultra-Bright LEDs I found were in a bag marked "RED" and are "no-name-brand" from China or India. They measure about 1.8V at 20mA. They have a clear package and make a blinding light beam about 20 degrees narrow. Red and orange Ultra-Bright LEDs are usually...
  19. audioguru2

    3V LED Chaser project

    Hi Ibernez, I just finished another 3V LED Chaser. This time I used orange Ultra-Bright low-voltage LEDs and they are really bright on-axis. I also used most of the changes that are in my 6V chasers. I added another trick to this one and probably all future chasers: the LEDs chase around and...
  20. audioguru2

    Audio signal generator

    Hi Travis, Voltage Control adds complication to your electronic drums project. Most VCO's have a continuous pulse or square-wave output that sounds like a "BUZZ", not a smooth sine-wave sound from a real drum. Therefore in addition to requiring a VCA or Envelope Generator to control its attack...
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