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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    The MC34071 is no longer made in a through holes package but the TLE2141 is.Can't you buy TLE2141 opamps and maybe a transformer online like everyone else? Go to www.farnell.com and click on the flag of your country or a neighbouring country to see what they have.
  2. audioguru2

    0-30V Stabilized Power Supply

    The original project has errors that can destroy the TL081 opamps and overload many other parts. That is why we fixed it and talk about the fixes in a few long threads in the forum. If the pins of Q1 are wired wrong and are mixed up then the reverse-biased emitter-base becomes a 8V zener diode...
  3. audioguru2

    Hi from your Newbie Guy ..... and my old Marantz Model SR 1000

    RX-300U. The owner's manual is in Google.
  4. audioguru2

    Hi from your Newbie Guy ..... and my old Marantz Model SR 1000

    I still use my 1964 HH Scott FM stereo receiver nearly every day. The only problem it had was a dial indicator light bulb burned out but it was easy to replace. My 1997 Yamaha stereo receiver has a worn out selector switch and its FM does not work anymore, even the FM display so it must be a...
  5. audioguru2

    Negative 0-30 Power Supply

    Simply build another power supply completely separate from the first power supply and use its "+" output as 0V and use its "ground" output as its variable negative voltage output. Even the transformer and any meters must be separate.
  6. audioguru2

    the finer points of electronics - II

    A transistor with the load at its emitter does not saturate and is not a switch. It is an emitter-follower. When it is turned on then its emitter voltage is a Vbe voltage drop less than its base voltage and its base voltage is probably not as high as its supply voltage. A transistor used as a...
  7. audioguru2

    wireless control of dc motors ie infa red

    This thread started and stopped 11 years ago. Today cheap remote controlled helicopter toys use two rotors and have a speed control for each for up, down and turning. They also have a speed and direction control at the rear for forwards and backwards.
  8. audioguru2

    Project: MAX6953 development board - where are the resistors?

    Many ICs regulate LED current without using series resistors. Examples are the LM3914, LM3915 and LM3916.
  9. audioguru2

    Phase shift detection circuit

    I just lit a white LED and a red LED with a current of only 24uA. They were not very bright but were very obvious. Try it. You can see in sunlight and you can also see in moonlight that has MUCH less light. Yes.
  10. audioguru2

    Project: MAX6953 development board - where are the resistors?

    The resistor value from the ISET pin to ground sets the LED peak current. You can also program the IC to change (maybe using PWM) the (average) current in each digit.
  11. audioguru2

    Phase shift detection circuit

    Texas Instruments say the 6N138 is obsolete. Its datasheet shows that its minimum transfer ratio is 300% (it is typically 1300%) so with an LED current of 1.6mA its minimum output current can be 4.8mA. But with a 5V supply and a 4.7k output resistor its output current is only 1.1mA so it will be...
  12. audioguru2

    HT12E and HT12D remote control

    This thread is also on at least two other websites. I think the 5V regulator is oscillating because the capacitors for the regulator should be ceramic and mounted much closer to the pins of the regulator.
  13. audioguru2

    Use 2v Signal to Control 12v LED strip

    The Sanyo transistor is fantastic and will work well in a new circuit to drive your LED strips but Sanyo was recently purchased by Panasonic and might not make transistors anymore. Now you are talking about a relay but forgot to tell us how much current its coil needs.
  14. audioguru2

    Use 2v Signal to Control 12v LED strip

    I think a little BC337 will get too hot with a current of 600mA and a saturation voltage loss of maybe 1.2V. Also its maximum allowed current is 500mA which is too low. The 12V battery might be 13.8V.
  15. audioguru2

    Use 2v Signal to Control 12v LED strip

    The new load will be 600mA. An ordinary transistor saturates fairly well when its base current is 60mA which is too much for an LED unless it is a big very bright one. So the receiver output must be analysed to see if it can be modified to supply 60mA.
  16. audioguru2

    Use 2v Signal to Control 12v LED strip

    We do not know how much current the 2V signal has. Therefore we do not know if you need a normal transistor or a darlington transistor. A darlington transistor has voltage loss that might dim the LED strips. Most Mosfets need a 10V input to turn on but some 'logic-level" ones need only 4.5V...
  17. audioguru2

    are BT2222 transistors the same as 2N2222

    A transistor is slowly damaged when operating with avalanche breakdown of a reverse-biased emitter-base junction. The 2N2222 and BT2222 are guaranteed to withstand a reverse emitter-base voltage of 6V or less. Both transistors probably have the same chip but since the BT2222 is in a tiny case...
  18. audioguru2

    Current monitor/sensor

    No. An emitter resistor is not needed for only one output transistor. Are you discharging a 12V battery? My circuit with an NPN driver transistor and NPN output transistor is a battery charger, not a discharger.
  19. audioguru2

    Current monitor/sensor

    You cannot change the voltage drop of R2 by changing its value. R2 quickly discharges the base-emitter capacitance of the output transistor and discharges its leakage current. 1k ohms is fine. A small thermal resistance allows a power transistor to increase its transfer of the heat to the...
  20. audioguru2

    Current monitor/sensor

    It will work well if the driver transistor has a fairly wide bandwidth like a BD139. In this forum there is a 0V to 30V at a few mA to 3A power supply. The improved version has two 2N3055 power transistors in parallel with emitter resistors and a driver transistor. When a slow TIP31 driver...
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