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audioguru last won the day on January 11

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About audioguru

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  1. I can buy a transformer with any voltage that I want. A 28VAC one or a 30VAC one will work in this modified circuit and the circuit will have a maximum regulated output of 30VDC at 3A. If you use a transformer that is 24VAC then the maximum regulated output from this modified circuit will be about 25VDC at 2.5A, and if the voltage and current controls are at maximum then the output will produce lots of unregulated ripple.
  2. I answered on the other website that your suggestion of using a tiny A23 12V battery will light 4 LEDs for only a few minutes and you might even see the LEDs dimming as the tiny battery runs down. Use eight AAA or AA alkaline cells in series instead. Buy Name Brand batteries locally because I think Amazon sells cheap Chinese batteries that have been leaking on a boat for ages.
  3. The datasheet shows how the output voltage is marked. It could be from 2V to 7V in 0.1V increments. I think yours is 2.3V.
  4. 31W a lot of power in the small area so the LED will get extremely hot. How will you cool it? A number of lower power LEDs will be easier to cool. An LED sets its own voltage that you cannot adjust. Its current sets its brightness.
  5. fm

    The circuit is too simple to be an FM radio.
  6. Why are you using the TIP122 darlington to short the 3V battery? The collector and emitter currents will be whatever the shorted battery current will be which might be 8A if the cells are new or be a few mA if they are old. The current gain of a TIP122 is a range from 1000 (the minimum) for some of them to maybe 10,000 or more for others. The Arduino output voltage at 3mA will be less than 5V, maybe 4V so the base current of the TIP122 might be 2mA. Your current meter has a voltage drop so it measures currents low. Maybe the Arduino pulses the Currents and your meter shows the lower average currents. The high current is not going into the Arduino, instead it is going from the battery into the TIP122.
  7. How do you know which ebay Chinese part is a fake and which one is real and good that will work?
  8. A local trustworthy electronics parts distributor sells good reliable parts. Some are made in China. The reliable parts are not bought on ebay by the trustworthy distributor. There are entire Chinese cities that make only fake electronic parts or they are factory rejects that are sold on ebay.
  9. Newark is also a good electronic parts supplier.
  10. Non-polarized electrolytic capacitors are available. Their high values might be the only type that is available. Ceramic capacitors have good high frequency response so they are used as a supply bypass to prevent an amplifier or voltage regulator from oscillating, but since their value changes with voltage changes or signals then they cause low frequency distortion if used as an audio coupling capacitor. Also they are microphonic and can cause background sounds or feedback squealing. I have never used expensive polypropylene capacitors for anything. I always use modern boxed metalized poly capacitors for audio coupling and they are not expensive. I saw expensive wound or rolled big polyester capacitors about 50 years ago.
  11. The ebay kit that is a copy of the original faulty Greek power supply on this site is also sold by Banggood and Amazon. Banggood is selling it at a clearance price since they probably had many complaints. They have modified it a little and are selling it again as a kit with a 28V/2A rating and an LCD meter for it. The very nice looking 30V/10A power supply is extremely cheap. Its ad has no detailed spec's. It does not even say if the voltage and current are regulated. If something looks to be too good then it probably is not true.
  12. You forgot to say if the 10V output from your power supply must be AC or DC. You also forgot to say if the input is AC or DC and its voltage and frequency. Did you know that the output power from your power supply will be 10V x 1000A= 10000 Watts? Where will it come from? What will it be used for?
  13. mAh is how long a battery will supply the current, not its maximum current. Besides, a load only draws as much current that it uses and not more unless it is shorted. Your car battery can provide hundreds of Amps to the starter when it is cold but the clock uses only a few thousandths of an Amp from the same battery and the clock does not blow up. A lithium battery cell is about 3V when it must be disconnected (or it is destroyed), to 4.2V when it is fully charged and no higher. Then two cells in series produce 6V to 8.4V. AA cells are 1.6V for new alkaline to 1.45V for fully charged Ni-MH. 8 in series produce 11.6V to 12.8V when new or fully charged. A special charger is needed for a Lithium battery. A low battery voltage must be detected and it turns off the battery. Use three Lithium cells in series for 9V to 12.6V or use a "boost converter" to boost the voltage of two cells.
  14. Your attachments do not work. Usually a circuit built on a solderless breadboard with messy wiring all over the place and intermittent contacts does not work. I have designed and built thousands of prototype circuits, some VERY complicated, soldered together on a compact stripboard layout and they all work perfectly. Your voltage jumping at a steady low frequency indicates "motor-boating" low frequency positive feedback. It might be a part that fails when it heats (overheats?) then works again for a while when it cools. Your attachements are actually links to All-About-Circuits where we must join to see them. Instead attach them here to your replies.
  15. The very simple kit should have told you what Vcc is and what Vi and Vo are.