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  1. Audioguru

    Solar charging 2400 mAh batteries

    Then people buy them online and throw away worn out ones in the garbage as landfill. .In Canada, libraries collect old batteries and send them to recycling.
  2. Audioguru

    Solar charging 2400 mAh batteries

    Very cheap Chinese solar garden lights used a 1.2V 600mAh AA size Ni-Cad battery years ago. in the past 5 or 10 years they use a 1.2V 300mAh or 600mAh AAA Ni-MH cell but I have a new one that has a 3.7V AAA Li-PO battery cell. Energizer AA Ni-MH cells were 2500mAh for years until they began to...
  3. Audioguru

    Solar charging 2400 mAh batteries

    Details are missing. What type of rechargeable battery? What size? Dave mentioned 1.2V Ni-Cad and Ni-MH but I thought the replacement was 3.7V Lithium which would make the lights too bright.. The battery type must match the charger circuit.
  4. Audioguru

    Looking for Collaborators!

    What is electronics going to be used for in agriculture? Zapping pests or lighting illegal plants? Google mentions Drones to view the yield, Sensors for temperature, humidity and soil water level and Auto-driving tractors.
  5. Audioguru

    Improve flat screen TV sound.

    Modern hearing aids play Bluetooth and can pickup the Bluetooth sound from a modern smart TV. My older hearing aids have a Bluetooth booster that radios to my nearby hearing aids but with no low frequencies. Vents in my hearing aid earmolds provide low frequencies that is normal with my hearing...
  6. Audioguru

    Vbe, Darlington Pair 3v?(?)

    Transistors have a range of specs. Some have minimum specs, some have mid and some have maximum specs. The maximum Vbe for the TIP140 is 3V at room temperature when the collector current is 10A (!) and the transistor has minimum specs. The graph in the datasheet shows 2V for one with mid specs...
  7. Audioguru

    BJT vs MOSFET for logic gates help

    Why don't you look at the datasheets for Cmos ICs? A CD4001 has 2-inputs NOR gates. A CD4071 has 2-inputs OR gates. Did you notice that there are no diodes and no resistors on real CMOS logic gates? Why are your inputs on the right side but everybody else has the inputs on the left side?
  8. Audioguru

    BJT vs MOSFET for logic gates help

    Tristan, why do you use the Source of your Mosfets as the output instead of using the Drain as the output like in Cmos circuits? What is the "C" in Cmos? It is "Complementary" which is P-channel and N-channel, not just one type. Here is a Cmos inverter that draws almost no current if it does not...
  9. Audioguru

    BJT vs MOSFET for logic gates help

    Tristan, do not read all the errors said by Ratstar. Tristan, since you want a non-volatile memory, then instead of randomly making one that has an extremely small capacity, buy a non-volatile memory chip? My camera and cell phone use very small low current non-volatile memory modules.
  10. Audioguru

    BJT vs MOSFET for logic gates help

    You said everything wrong. Please read about it before saying wrong things. 1) The gate-source of a Mosfet is a capacitor with no resistance. The capacitance makes it difficult to switch quickly since charging and discharging speed needs a fairly high current. It can be switched slowly with an...
  11. Audioguru

    BJT vs MOSFET for logic gates help

    A Mosfet uses an electric field (that is why it is called a Field Effect transistor) and has no resistance between its gate and source. A Mosfet has a fairly high gate to source capacitance. So when the Mosfet is turned on with a voltage on its gate then the voltage stays there when there is...
  12. Audioguru

    Graphic equalizer

    Why do you need EQ? Is it because you have cheap garbage speakers? I designed and built and modified purchased speaker systems to sound good. The only EQ I use is a bass boost circuit for my smaller speakers.
  13. Audioguru

    Improve flat screen TV sound.

    The sound from most TVs sounds awful. For my TV's I have the line level stereo outputs driving my home-made amplifier and speakers on one TV and I use a stereo sound system I bought for the other TV. My slightly modified clock radio with home-made eternal speaker also sounds great. I have...
  14. Audioguru

    Speaker & Amp Impedance Question

    With a motor, if you short it then its generated power quickly stops it. The same with a speaker, an amplifier with a very low impedance shorts the speaker coil (a speaker is a motor that moves its cone and the air around it) when the signal stops, then it quickly stops vibrating.
  15. Audioguru

    Speaker & Amp Impedance Question

    Impedance is a resistance to AC. A speaker with an 8 ohms impedance has a resonant impedance of about 70 or 80 ohms at a low frequency. When it is resonating then its coil is moving back and forth with its magnet and is becoming an AC generator. The extremely low output impedance of a modern...
  16. Audioguru

    Speaker & Amp Impedance Question

    A speaker and a resistor in series both conduct exactly the same current. 2A in a 4 ohm resistor and in a series 4 ohm speaker drives and heats the resistor with (2A squared) s 4 ohms= 16W and heats (dissipates in) the speaker also with (2A squared) x 4 ohms= 16W. Since a speaker has a strong...
  17. Audioguru

    Henri Abrahams astable multivibrator

    The transistors have the correct polarity but they are the wrong type of transistor. The circuit uses NPN type of transistors but the wrong type shown is PNP. Also the LEDs do not have current-limiting resistors. The base resistor values are so high that transistors with low hFE (110) will...
  18. Audioguru

    SW radio using OP amplifier

    He talked about using an old Mickey Mouse "regenerative" detector but did not show it Using his very old 741 opamp as a power amplifier to drive an 8 ohm speaker then its 12mA peak output current will be 8.5mA RMS resulting in a very low maximum output power of only 0.0006W. Hold the speaker...
  19. Audioguru

    Henri Abrahams astable multivibrator

    I looked in Google for the transistor multivibrator with the LEDs at the emitters and found only the one linked above. It might not work especially when the battery voltage is low. I also found a circuit with two serious errors.
  20. Audioguru

    Henri Abrahams astable multivibrator

    I think that Ratstar does not know that the maximum forward-biased base-emitter voltage is only 0.6V to 0.7V then the capacitors do not charge "backwards".
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