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  1. audioguru2

    Understanding Vce & Vbe (newbie)

    Hi Prateek, A modern (expensive) Mosfet has a very low on resistance so it ts much less when used for switching, than a BJT. I think a Mosfet is more linear. A Mosfet doesn't have thermal runaway like a BJT. A power Mosfet is capable of operating at higher frequencies than a BJT. I can't think...
  2. audioguru2

    Camping Music Box - PROJECT

    Yeah, the LM4651 and its controller mate are easy to make. National was going to cancel them this year but extended the cancellation until next year.
  3. audioguru2

    BJT power supply

    Hi Alun, I think a big output capacitor or small one at the collector of Tr3 to ground will compensate it pretty well. ;D
  4. audioguru2

    Camping Music Box - PROJECT

    Good idea, Alun. ;D TI have a nice "240W" class-D amplifier IC. It would provide about 35W into a 4 ohm speaker at clipping with a 24V battery and is so efficient that it doesn't need a heatsink. It has 36 pins and is a tiny surface-mounted thingy so it would be difficult for Stuee to solder. I...
  5. audioguru2

    Sequential Timers with PWM Motor Speed Control

    That's brilliant and I didn't think of using a Schmitt trigger oscillator as the triangle-wave generator. I could have saved a dual opamp! ;D Yeah, I use the regulated 5V for the voltage controlled oscillator and the full 8.4V for the Mosfet and motor. The battery is actually about 10V when...
  6. audioguru2

    Camping Music Box - PROJECT

    Hi Stuee, You can use an amplifier designed for a car radio and power it from a motorcycle battery: The TDA1552 is a simple circuit that will provide 12W per stereo channel at clipping into 4 ohm speakers. The TDA1564 is very efficient since it switches fom single-ended at low power to bridged...
  7. audioguru2

    Sequential Timers with PWM Motor Speed Control

    Hi Ante, thanks. ;D Its wingspan is only about 80cm, but the wing is wide and thick so the plane will fly slowly. The motor draws 3A for only a couple of seconds 'til the plane gains speed, when the load on the motor is reduced and its current drops. Then the sequencer will reduce the motor's...
  8. audioguru2

    Sequential Timers with PWM Motor Speed Control

    Hi Alun, thanks. ;D Because I have some TLC555 and LMC555 single timer ICs and I know their pin-out. I didn't make the elevator control circuit after going to the hobby store to buy a servo and was told that it would strip its plastic gears if it was without power. I was going to use it only to...
  9. audioguru2

    Sequential Timers with PWM Motor Speed Control

    Hi Guys, I've finally finished building the electric model airplane I won. ;D It is styrofoam and had a lot of parts to be joined with special glue and epoxy. I painted it with 4 brushed coats of shiny "red hot" latex house paint. It has a 3A geared electric motor that swings a 10" prop and is...
  10. audioguru2

    Camping Music Box - PROJECT

    Hi Stuee, Doing some number crunching with your 6V rechargable battery and 100W requirements, if the amp is 60% efficient then it will use 167W and pull about 28A from the battery. The battery charge might last only a few seconds. Your amp will need a DC to DC stepup converter (like a...
  11. audioguru2

    Delay Timer !!!EMERGENCY!!!

    Just use a coupling capacitor in series with the trigger switch so that it gives a short trigger pulse no matter how long you hold down the switch. If the 555 timer's pin 2's pull-up resistor is 10k then use a 0.1uF coupling cap. ;D
  12. audioguru2

    Outdoor Light Status Indicator

    Hi Robert, Most red LEDs are 1.7V to 2.0V. Blue, green and white LEDs are 2.9V to 3.9V. You can purchase LEDs with a built-in current-limiter that are designed for 5V or 12V but certainly not 110V. Use the full-wave bridge rectifier with a capacitor for 110VAC. ;D
  13. audioguru2

    Outdoor Light Status Indicator

    I think that using a full-wave bridge rectifier is best so that the LED doesn't flicker. ;D
  14. audioguru2

    need help... urgent!! plzzzzz

    You forgot to attach the diagram. Dis is its schematic:
  15. audioguru2

    Detecting the resonant frequency of a LC circuit?

    Hi AnD, You can use a CD4046 or 74HC4046 as a phase locked loop and it will give frequency control and indication of when the LC circuit's total voltage and total current are in phase by using the IC's phase detector II. The phase of the current is sensed by a low value resustor in series with...
  16. audioguru2

    Outdoor Light Status Indicator

    Hi Ante, Yeah, I'm going to be an old and bold technician by trying a 2A current through my LEDs that have an absolute max instantaneous current rating of only 100mA. If I use a blue LED, do you think the bonding wire will glow orange brighter than the LED? ??? ;D Do you think the junction will...
  17. audioguru2

    Outdoor Light Status Indicator

    Hi Robert, Who is rigid? My circuits are designed within manufacturer's ratings and work fine without blowing-up. I have lots of fun blowing-up backwards high-value electrolytic capacitors. When I was young I made capped pipe-bombs that went off like rockets, and open-ended pipe-rockets full of...
  18. audioguru2

    Electronic Stethoscope

    Hi AAronopolis, I like tis circuit, the modified one should work well. You have the pot wired incorrectly without ground on one of its terminals. Pin7 of U1b and pin3 of the 741 are the same piece of wire, the input to the pot's single input terminal when the volume control is at maximum, the...
  19. audioguru2

    Understanding Vce & Vbe (newbie)

    Yes, the switch-off is a little slower but you might not notice. Selcet a zener voltage about the same or less than the max voltage rating of the transistor driving it. Click on the Articles button at the top of this page and find and click on SCR in the index. ;D
  20. audioguru2

    need help... urgent

    Hi Ann, I think you are talking about the "Park-Aid" project in our projects section but forgot to link to it like this: http://www.electronics-lab.com/projects/automotive/005/index.html A 1uF capacitor is very common and should be available just about anywhere. I have 50V electrolytics and 63V...
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