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  1. Herschel Peeler

    Hello from Belgium

    What problems are you having?
  2. Herschel Peeler

    12V Rechargeble Fan Circuit Problem

    Do you have a meter and know how to check transistors and diodes?
  3. Herschel Peeler

    Formulas for Voltage, Current and Resistors

    One example uses a 100 ohm resistor. The other uses a 10 ohm resistor. Either approach is good.
  4. Herschel Peeler

    Circuit design help needed

    Can you deal with a microcontroller based design? Are you looking for somebody to build it for you? Do you already have a basic design in mind?
  5. Herschel Peeler

    Determine the Vcbo of a germanium transistor and the voltage drop along the connected components.

    Theory aside, I built a version of the circuit. I didn't have a germanium NPN but I had a germanium PNP, so I flipped it and used a germanium PNP and a silicon NPN. Yes I can get enough leakage in the germanium PNP to get the LED to turn on. My germanium was a 4JX1D872. Measured leakage at 5 V...
  6. Herschel Peeler

    Voltage regulator for LED panel

    Battery powered?
  7. Herschel Peeler

    Voltage regulator for LED panel

    A problem with using the LM2596. LEDs are 3.5 V. The battery is3.7 V. The LM2596 needs a few volts in higher than the out. Why use the LM2596 if the battery is at the right voltage in the first place? No the LEDs won't blow out at a volt or so over the 3.5 V. Most LED flash lights run the 3.5 V...
  8. Herschel Peeler

    Voltage regulator for LED panel

    I think there is nothing bad about your original idea. You only need about 2 Amps. TheLM2596 can supply 3 Amps. Put a small resistor in series with each LED, maybe 10 to 27 Ohms or so. You can't run it from USB. How long will the light be on at any given time? Just a few minutes? If hours the...
  9. Herschel Peeler

    Can someone please explain this circuit for me?

    I don't grasp the reasoning for returning the inverting input of the amp to the center of the Zeners instead of ground.
  10. Herschel Peeler

    Can someone please explain this circuit for me?

    Good point. I didn't look at that. For the original poster, SOA is Safe Operating Area. It depends on the maximum voltage across the transistor and the allowable current through it. Not really much to calculate, just look at the graph. Voltage x current = watts being dissipated. Derated for...
  11. Herschel Peeler

    Can someone please explain this circuit for me?

    Is something like this what you were looking for? TR1, the two 1N4148 diodes and the 150 ohm resistor are a constant current source. One diode cancels out the 0.6 V or so across the E-B of TR1, the other diode sets the voltage across the 150 ohm resistor. 0.6 V / 150 ohms gives a consistent 4...
  12. Herschel Peeler

    12V DC convert for 9V DC

    LM7809T and wire. (edited to add ...) Oops, couldn't find a source for one of those. LM7808T will get you to 8 V. Available from Jameco Electronics for about $0.35. Another possibility is an LM317T and a couple of resistors, If I supplied a schematic could you build it?
  13. Herschel Peeler

    Chaining HCF4094 Shift Registers

    An example
  14. Herschel Peeler

    op amp supply voltage

    Another thing to watch is the range of input and output voltages. The LM741 does not work well within a volt or two of the power rails. So trying to run it at +/- 1.5 V is impossible. Even from +/- 5 V you may only get a signal of +/- 3 V in or out. I don't know off hand what the TL071 is like...
  15. Herschel Peeler

    Oscillator or Not?

    An interesting experiment. D grass seeds have a permanent magnetic dipole moment? Do grass seeds contain iron? In a strong magnetic field will the iron get hot and "cook" the grass seeds? How strong a magnetic field are you considering? How are you going to shield the non-exposed seeds?
  16. Herschel Peeler

    Oscillator or Not?

    Is your question "is 150 Hz hazardous" or "is 50 or 60 Hz hazardous"? How strong a field? What do you expect to get out of a 9 V battery? or how long an exposure? Your goal is a good one. Ds you think "no harm to grass seeds" will prove "no harm to humans that have a nervous system"? Might...
  17. Herschel Peeler

    I am to design a switched mode psu without IC components.Help please

    Are you limited to material covered in the classroom?
  18. Herschel Peeler

    choosing a resistor value

    Why do you need an Arduino? Are you going to monitor this level over time? If you just want to know there is water no smarts are necessary.
  19. Herschel Peeler

    Inside a 555!

    Most excellent. Thanks for posting that.
  20. Herschel Peeler

    I am to design a switched mode psu without IC components.Help please

    You teacher is hard? If you want to accomplish big things do not surround yourself with people who ask too little of you.
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