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  1. audioguru2

    Electronic Stethoscope

    Hi RG, Time is running out and you have not given us any details about what you executed. The above mods should make it work well. Of course, it is designed for a 2-wire electret type microphone that is connected to the circuit with shielded audio cable. Recently, people are confused about the...
  2. audioguru2

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

    Hi Dylan, Welcome to our forum. Most of my recommended mod's are with the Parts List. I have posted very detailed updated Parts Lists here for the 5A version, and in the other thread for the 3A version. The changes to the schematics are very simple: 1) Replace the rectifiers D1 to D4 with a...
  3. audioguru2

    ultrasonic mosquitoes repeller

    Hi Vedran, Yeah, those expensive propane-powered mosquito catchers produce a huge cloud of CO2 and suckin the mosquitoes that are attracted to it. I think that they are also attracted to our heat and odour, so that they don't try to suck blood from the chairs that we are sitting in. The experts...
  4. audioguru2

    0-20 (3A) and 0-40 (1.5)A Power Supply (Elenco)

    Hi Inferno, You want to modify that PSU to do much more than it was designed for? You might as well select a PSU that does what you want. Transformers, rectifiers, filter capacitors, number of output and driver transistors, heatsinks, resistors' power rating, etc., etc. Oh man!
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Kevin, The voltage regulating zener diode, D8, is in the feedback loop of the very high gain opamp, U1, and together make a very good voltage regulator of 11.2V. The high gain of the opamp makes certain that the current through the zener is constant, regardless of how much the supply voltage...
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi TattooDan, Welcome to our forum and greetings to Japan. You can replace the voltage adjustment pot in this project with a switch and some series resistors that total about 10K ohms. The ratio of the resistors determine its output voltage. My sketch is here:
  7. audioguru2

    REALLY High Voltage Arcs

    Hi All, Ante posted one before, but here is a link to pics and movies of high voltage disconnecting arcs and other disasters. They have detailed descriptions: http://205.243.100.155/frames/longarc.htm#Disconnect
  8. audioguru2

    solar powered toy car

    Hi Ante, Do you think that Herman wants to break a speed record (speed of sound?) and will need only a couple of hundred Watts?
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Emiliano, Good, now you can replace the over-heated 2N3055 with two of them, with a 0.1 ohm, 1W emitter resistor each, mounted on a very big heatsink. Q2, the little 2N2219, will also overheat, and should be replaced by a heatsinked TIP31A power transistor. Its pinout is different. You may...
  10. audioguru2

    solar powered toy car

    Hi Herman, Why don't you try the car with alkaline or rechargeable batteries first, to determine its power requirement. Then you may find that solar cells to power such a heavy car will be too big and expensive.
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Emiliano, Did your project work good before but recently fail? With the 2N3055 disconnected, if the output voltage goes up and down with adjustments of the voltage control, but stays at 29.8V with it connected, then I think that the 2N3055 has a leaky or shorted collector-base junction. Maybe...
  12. audioguru2

    Passive audio filters

    Hi Vainajala, It is no wonder that your curves look so messed-up. You were measuring the room's reflections, not the speaker's response. If you move the speaker or microphone only 10cm, the results will change. That's why I measure my speakers outdoors, pointing straight up, where there are no...
  13. audioguru2

    Smartkit order

    Well, let's see about them: 1) They don't answer their e-mail (the Olympics are over!). 2) They don't care about their schematics. 3) They have a power supply kit that has problems. Is this a good company to order from?
  14. audioguru2

    Pulse Width Modulation DC Motor Control

    Thanks, Sasi, Not only does your circuit control the motor's speed very well with PWM, it reverses its direction, too! ;D What would happen if you rev'd the motor full speed forward, then quickly slammed it into reverse? Over-temperature shutdown of the tiny IC?
  15. audioguru2

    Pulse Width Modulation DC Motor Control

    Thanks, GPG, Of course your circuit will produce PWM and control the motor's speed by adjusting the pot. The diodes allow the oscillator's output duty-cycle to be varied over a wide range while keeping its frequency constant. The paralleled inverters at its output charge the Mosfet's gate...
  16. audioguru2

    Ignition coil driver circuits and experiments

    Hi Ante, Here is a high voltage limitation that we haven't discussed: The spark coil's core is going to saturate with a particular amount of current through its primary, which is determined by the voltage that is applied to it. Then applying more voltage than that won't make any difference to...
  17. audioguru2

    Pulse Width Modulation DC Motor Control

    Hi Ante, Never mind your darn simulator. Just quickly build this simple circuit. My point is that it does not produce Pulse Width Modulation because it is just a variable frequency oscillator with a constant duty-cycle. The author says, "This (is a) simple pulse width modulation DC motor...
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Inferno, Of course this project has short circuit protection. It will current-regulate whatever setting of its current pot, and if it is set high, will test the quantity of output transistors and their heatsink that you use, because they will get very hot. Measure load regulation by...
  19. audioguru2

    Ignition coil driver circuits and experiments

    Run for cover! Steven is close to producing mega-volts! ;D Hi Steven, Adding a "condenser" across the transformer's primary might make it even better. I know, you are thinking about rectifying the mains, and using the 340VDC to power the spark-coil's primary, aren't you? ;D
  20. audioguru2

    Trying to build a project, need parts

    Hi Stu, Those are very common parts over (up?) here for many years. Many Aussies have given up with RS Components' and Dick Smith Electronics' war-surplus stuff, and order from Farnell's free catalog or on the web. I use my country's division of Farnell and get next day delivery. My country is...
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