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Posts posted by audioguru

  1. 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?

  2. 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. 

  3. 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.

  4. The cheap Chinese solar garden light has a dim light for only a couple of hours following a sunny day. It lasts only a couple of months before its LED, solar panel and battery rust away. No light following a cloudy day. The cheap solar panel actually gets sunburned.

    Use the pcb circuit from a solar garden light and amplify its output with a transistor to drive a bright high current LED. Use a larger high current high quality solar panel and battery. Properly seal everything to prevent rust. 

  5. Solderless breadboards cause many problems reported on all the electronic forums. The many tangled wires and rows of contacts have capacitance between them that cause many electronic circuits not to work properly. The contacts are frequently intermittent.

    I made thousands of prototype circuits soldered on stripboard where the strips of copper were cut to length with a drillbit plus a few jumper wires form half a pcb and the components form the other half. Every circuit worked perfectly and many looked good enough to be sold as the finished product.     

  6. To use your transformer then many resistor values will need to be re-calculated and changed. The 16.6VAC will have a peak voltage of only 23.5V. The improved circuit is designed to use a 28VAC/4.3A or 30VAC/4A transformer. If you re-design the circuit then with your transformer its maximum regulated output will be about 16.5VDC at about 1.5A. 

  7. Here in Canada (and in the USA) FM radio station frequencies are at odd frequencies like 99.9MHz, 100.1MHz, 100.3MHz so 100.0MHz is not used. Even frequencies like 100.0MHz, 100.2MHz and 100.4MHz might be used in Europe.

    If you use a quartz crystal oscillator and a harmonic of it at 100.0MHz then the accuracy depends on the spec's for the crystal. 

  8. I do not know which circuit the ebay pcb uses, maybe it is wrong. The original circuit and the ones modified on this website use a 0.47 ohm current sensing resistor R7. Then when the current setting pot is turned to maximum the current is limited to about 3.0A. The Chinese modification for the Banggood kit might do it differently. 

    current setting.png

  9. Hi Army Vet.

    Did you build the original circuit or the modified circuit? Which power transformer and opamps did you use? The dim power LED indicates that the transformer voltage is too low maybe because it is overloaded with something shorted or because the rectifier diodes are connected wrong. Maybe the main filter capacitor is connected backwards?


    When the current regulator light is turned on what is the load, the voltage setting and current setting?


    When the output voltage is 1V what is the load, the voltage setting and current setting?  

  10. An audio amplifier with a supply voltage as high as 200V will produce about 500W into an 8 ohm speaker and produce almost 12A peak, not a few milli-amps.

    Oh, is your amplifier going to use an old output transformer that has not been used for 50 years? Then its output power might be 1.8W into 8 ohms. 

  11. It sounds awful like a squeaker, not like a speaker because the speaker is too small and it is not mounted in an enclosure.

    The LM386 amplifier produces only 0.11W (almost nothing) into 8 ohms when its supply is only 5V. 

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