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  1. audioguru2

    key chain laser power supply

    Who, me? Lotsa people say that. ;D It depends on how long ago you had a bath. Don't you have long hair and ride a noisy motorcycle? ;D I don't think it will work. All my LED thingys have a very low duty-cycle to save power, and chances are that the satellite will take my picture during the LED...
  2. audioguru2

    Analyzing my amplifier project

    You were given a 100pF trimmer cap, one million times smaller than 100uF. With the 100pF trimmer cap, it can't have any gain at audio frequencies. Use a real 100uF capacitor for C4 and measure the gain. The datasheets for power transistors don't show data for such low currents. The little 2N7000...
  3. audioguru2

    key chain laser power supply

    Click on my link: http://maps.google.com Then use the zoom on the left to zoom out to see the whole world. Double-click on a spot to center it then zoom in. Click "satellite" and it shows a photograph. Do an address search. It gets very close for North America and England but Australia and other...
  4. audioguru2

    transistors

    Hi Prateek, I don't think beta affects a transistor's voltage gain. It affects a transistor's input impedance and input bias current. A common-emitter transistor's voltage gain is simply Rc/Re, where Rc is its collector resistor in parallel with its load. The voltage gain is higher at higher...
  5. audioguru2

    555 Based Flyback/Ignition Coil Driver

    Hi Ante, A typical 2N3055 has a beta of 35 at a collector current of 4A and a Vce of 4V. Its minimum but still guaranteed beta is only 20. Its saturation region is another story. It ain't going to saturate without a whopping high base current. ;D
  6. audioguru2

    key chain laser power supply

    Hi Steven, I am Uncle Audioguru, you know, the guy with a big skunk that tries to get under my porch. Ante is the other bad guy! ;D My neighbour got back from a vacation yesterday. A whole new family of skunks was found under their porch. I have concrete blocks now to keep them out and it...
  7. audioguru2

    Analyzing my amplifier project

    Hi Shaiq, You can't use a power Mosfet as a low-level preamp. You need a few small ordinary transistors or an opamp. 1) You are using a power Mosfet in your low-power circuit. The IRF510 is rated for 4A, but your circuit's max is only about 2.6mA. The datasheets for power transistors don't show...
  8. audioguru2

    Voltage that drives the speakers

    Hi Shaiq, Audio is AC, not DC. A microphone produces about 10mV AC. A preamp amplifies it to about 1V AC. A speaker power amplifier amplifies it to 20V AC for 50W into an 8 ohm speaker. These are RMS sine-wave voltages. Peak-to-peak voltages are 2.828 times more. If you apply DC to a speaker...
  9. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Maksar, In the datasheet they show a derating graph for the amount of power a 2N3055 transistor can dissipate when its case is at a certain temp and its junction is at its absolute max temp. My graph shows 115W if its case is 25 degrees (impossible), about 65W if its case is 100 degrees, and...
  10. audioguru2

    Speakers

    Hi Steve, Welcome to our forum. ;D I bought my 1st set of decent speakers before I learnt how to make them. I went to my local stereo shop and listened to many very expensive speakers. Some sounded fantastic to me, while others I didn't like. Then I listened to less expensive speakers, and only...
  11. audioguru2

    key chain laser power supply

    Yes, with only 9V. But your schematic shows two 18V batteries. +9V and -9V is an 18V battery. You should draw the single 9V battery or call its terminals +9V and GND. ;D
  12. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Maksar, With this project driving 5A into a low voltage or short, its 3 output transistors will dissipate a total of 190W, or 63W each. The thermal resistance of a T03 2N3055 is 1.5 degrees C/W, an insulator is 0.7 and that heatsink is 1.4. The total thermal resistance would be 3.6 degrees...
  13. audioguru2

    transistors

    Transistors with a beta as high as 900 is the highest I've seen and they work about the same as transistors with lower beta, except the input bias current is very low and the input impedance is high. BC549C for example. Some opamps use "super-beta" transistors on their inputs for a very low...
  14. audioguru2

    conversion from miliohms to voltage circuits

    Resistors with a value of 0.1 ohms, 0.22 and 0.33 ohms are commonly used as emitter resistors for the power output transistors in audio amplifiers.
  15. audioguru2

    key chain laser power supply

    Hi Steven, Your schematic shows four 9V batteries. 2 in series for 18V for the photodtector/transistor, and 2 more in series for the 390 0hm resistor in series with the LED. It is very confusing when it shows "-9V" instead of ground. ;D
  16. audioguru2

    key chain laser power supply

    Hi again, I use http://maps.google.com to measure the range of my stuff. It's too bad it its fine detail is only for North and South America and England right now. I can see the map or switch it to a satellite picture. I was excited to spot my house with my car in the driveway and my son spotted...
  17. audioguru2

    key chain laser power supply

    Hi Steven, How far is its range? I got a laser pointer in a pen and it can light-up a car's reflective licence plate at night very far away. The reflection is nearly blinding. If your 9V batteries are new, and the forward voltage drop of your red LED is 1.8V, then you are feeding 41.5mA through...
  18. audioguru2

    conversion from miliohms to voltage circuits

    Hi Jess, Welcome to our forum. ;D To convert from milli-ohms to voltage, put a known current through the resistance and measure its voltage drop with a voltmeter. That's what an ohm-meter does. Since the voltage will be small, it can be amplified with an opamp.
  19. audioguru2

    Cold Heat Soldering Tool

    It is not a welder, the tip is a low value resistor with two contacts. Bridge the contacts with something conductive and the tip heats. If it has enough voltage to light an LED and it has enough current to get hot, then it will light-up the base-emitter or base-collector junction of a transistor...
  20. audioguru2

    transistors

    Why? An opamp circuit doesn't have to have high gain. Its negative feedback reduces its extremely high open-loop gain with two resistors to however much gain you want. The extra gain makes the opamp an error amplifier so that any non-linearity in its output is reduced to very, very close to zero.
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