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  1. audioguru2

    Power supply for AMP in CAR

    Hotwaterwizard, Good point about spike protection! I was trying to figure out how a positive spike at the collectors of the output transistors can get through their turned-off collector-base junction, and how a reversed-biased diode can arrest this spike. Now I realise that the positive spike...
  2. audioguru2

    Night rider scanner

    In order to avoid continuing confusion about knightrider/chaser, for those who have not seen the American TV show, is it possible to include the animated GIF: into the project article, above? Is it also possible to remove the phrase,"Knightrider" from the Projects Index for the chaser circuit...
  3. audioguru2

    basic capacitor question

    Hi Mike, Welcome to this community. So far, you have gathered most of the information that you need: 1) You have a power supply with a full description and its ratings. 2) You described a purpose: a certain time delay before energizing the load. 3) You know that a capacitor takes time to charge...
  4. audioguru2

    0-30 Vdc Stabilized Power Supply

    Mastrila, Your variac, isolation transformer and rectifier diodes probably are not made to have a low voltage drop during the brief but HUGE current surge when the filter capacitor, C1, is re-charged. Therefore the voltage across C1 (at the lowest point of its ripple) probably is too low. Let's...
  5. audioguru2

    Power supply for AMP in CAR

    MP, I did not see any function for diodes D3 and D4 since they are always reversed-biased. Pull-down resistors having only about 20mA were suggested to replace them for reasons as follows: 1) To turn-off the output transistors, fast. Without pull-down resistors, the bases of the output...
  6. audioguru2

    Power supply for AMP in CAR

    Hotwaterwizard, I am sorry, but I made errors when I suggested modifications to your project: 1) DO NOT add diodes across the transformer's primary. 2) DO NOT add 8 ohm resistors in series with the bases of the output transistors. My reasons are explained in the other inverter post here...
  7. audioguru2

    555 - 556 IC tester

    Steven, I hope that you were not offended. I, too, am sorry for my comment and retract it. I hope that my suggestion to use 1 socket and 4 LEDs proves to be useful here.
  8. audioguru2

    Night rider scanner

    Mixos, Steven's circuit is not a knightrider, it is a chaser that misses a few steps. We have discussed knightriders and chasers recently in this site at: Electronic Projects Design/Ideas, "LED Flasher (very interesting)". In Steven's circuit, R5, the LED current limiting resistor, is not needed...
  9. audioguru2

    Power supply for AMP in CAR

    Hotwaterwizard, Your inverter design is coming along, but I have some suggestions: 1) D3 and D4 don't appear to do anything. I suggest replacing them with 100 ohm, 1/4W resistors so that the bases of the output transistors have a pull-down instead of a float-down. 2) Add diodes in series with...
  10. audioguru2

    555 - 556 IC tester

    That's a nice way to test a 555, but 2 sockets for a 556? I think that I'd combine the 2 sockets into 1, so that there are 4 LEDs. I can't wait to see how he tests a hex inverter, an octal latch or a memory chip!
  11. audioguru2

    Power Supply +5v with Zener

    Kevin, Sorry to correct you again, but the zener gets its current through R3 from the unregulated input on the left, not the regulated output on the right.
  12. audioguru2

    Radio control glow engine 'glow driver'

    In my plane-days, I used a #6 dry cell. Have you seen one? 1.5V and it weighed about 4 pounds. When the engine wouldn't start then it was time for a new battery. I might try an electric plane this summer, but instead of Radio Control, I'll use a timer to control PWM motor speed control, and let...
  13. audioguru2

    Power Supply +5v with Zener

    Are you talking about the regulator circuit that Siddharth attached in his reply #17? I've seen that circuit many times, it works fairly well. Build one, test and study it.
  14. audioguru2

    Light Switch

    Siddharth, I am glad that you figured how to calculate the resistors. But a 7805 won't work with only 3V because it needs at least 6.5V. I suggest powering it with 6 cells which give 9V when new, and 6.6V when exhausted. Use a 9V torch bulb. This circuit is going to eat batteries quickly.
  15. audioguru2

    Power Supply +5v with Zener

    Ante, Your experiment inspired me to try it too, and then I continued experimenting: 1) New 9V alcaline battery feeding a 7805 with no load. Current drain = 6mA. Its been going a day-and-a-half now, and its battery measures 7.8V. The regulator feels cold and its output measures 5.05V. 2) I made...
  16. audioguru2

    Power Supply +5v with Zener

    Siddharth, Thanks for helping Kevin, and your circuit will work here too. When I unzipped your file, I was surprised that the simple schematic uses more than 1MB of memory.
  17. audioguru2

    741, TL071, LF351, NE531, TL061, TL081 IC tester

    Testing cheap opamps? I designed an audio equalizer that adjusted the levels at 7 frequencies, to flatten the response of a new loudspeaker. I also designed a complicated tester for the circuit which automatically stepped through many specs such as current drain, output noise, harmonic...
  18. audioguru2

    Power Supply +5v with Zener

    Siddharth, Why use $3.00 of parts making a medioker regulator, instead of using a 7812 for only $.52 that has superb regulation?
  19. audioguru2

    Light Switch

    Siddharth, Thanks for telling to us the application and all of your requirements. Your original circuit will not do what is required if you connect an unknown quantity of incandescent lights between the output of the regulator and ground: 1) The regulator will shut-down if you try to power too...
  20. audioguru2

    OPAMP questions

    Kevin, A compensated opamp works VERY well when used within its simple rules and specs. Don't try to build your own opamp from scrach, just use the ones that are so popular. The only problem that I have ever had is that some opamps oscillate at a very high frequency when driving a shielded audio...
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