audioguru

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audioguru last won the day on January 11

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  1. A zener diode is used with reverse bias voltage. A temperature sensing diode is used with forward voltage that is completely different. Look at the datasheet of a 1N4148 diode. Its forward voltage is shown at -40 degrees C, at +25 degrees C and at +65 degrees C. The forward voltage drops as the temperature of it rises. Test it at a current of 0.1mA to 10mA at different temperatures.
  2. The circuit will never have a negative voltage in it. P1 will smoothly give 0V to +5V to pin 2 as it is rotated. The input current of pin 2 is so low that a 10k or 20k pot will make no difference. R4 limits the T1 base current to only 0.3mA then tie relay might not be activated if it needs 6mA or more. The current in R4 must be at least 1/20th the current in the relay coil. The BC547 works poorly at currents above 50mA.
  3. You mentioned relays. Then you do not want speed control? Jerky on-off is called "bang-bang control" in cheap kids toys. What will happen to the motor when it is running forward at full power then you suddenly change it to run in reverse at full power? The fuse will probably blow to save the motor. You need a circuit to delay switching directions.
  4. You forgot to attach the schematic of your circuit for us to see anything wrong.
  5. A 24V transformer has a voltage too high for the TL081 opamps. Use a transformer with a lower voltage like 15V. Replace the opamps that were strained. Replace the old fashioned 2N2219 with a modern BD139 transistor on a real heatsink. Replace the single 2N3055 output transistor that might be shorted. Re-calculate the values for the resistors that set the voltage and current.
  6. The original project has many parts that are overloaded and they fail soon. We modified it to make it work better and to be more reliable.
  7. We will help you if you build or design a circuit that does not work properly. But it sounds like you want somebody to design a circuit for you. Somebody might do it.
  8. We talked about fixing the cheap Chinese Banggood kit on another website and I do not want to talk about it again.
  9. I think the kit from Banggood and copies of it are selling at a clearance price today because it has been replaced with a better kit maybe with its errors corrected. Of course the new kit costs much more and comes with voltage and current displays.
  10. The original circuit has many overloaded parts and cannot produce 30VDC at 3A. It is also missing the calibration trimpots that are used in the improved version that can be set to exact maximums of 30.0V and 3.0A.
  11. None of your voltages match. The solar panel produces only 0.5V. The battery produces only 3.7V and is charged from about 5V or 6V. The pump needs 6V. A battery charger does not dump power when the battery is fully charged. It simply turns off the charging.
  12. Nope, your math is wrong. 104 is 10 followed by 4 zeros making 100000pf which is 100nF which is 0.1uF. 222 is 22 followed by 2 zeros which is 2200pf which is 2.2nF which is 0.0022uF. The highest value for a ceramic disc capacitor I have seen is 1uF so use an electrolytic type for 50uF. My multimeter measures capacitance. It also measures frequency, AC and DC volts, current, resistance, continuity and forward voltage of a diode. The AC is measured with True RMS and it automatically switches its ranges when I want it to do it.
  13. ebay means "manufacturer's rejects" and "sweepings off the floor". Don't buy anything from ebay, instead buy from a reputable and reliable Western electronics parts distributor. Haven't you see a datasheet of an old 2N2222 transistor? Like all transistors its hFE is a range of 1 to 3 times and the actual hFE also varies with the collector current. With a collector current of 1mA the minimum hFE is 50 with no guaranteed maximum hFE. With a collector current of 150mA the hFE is guaranteed to be from 100 to 300. hFE is DC current gain that is listed and shown on a graph on a datasheet. hfe is AC current gain that is usually a little less than hFE at low frequencies and is usually not shown on a datasheet.
  14. 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.
  15. 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.