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  1. crutschow

    WallWart conversion...

    No matter how you drop the voltage (unless you use a buck regulator) there will be the same amount of power (which generates heat) that has to be dissipated, whether it's in a linear regulator, resistors or diodes. In this case three series diodes is the easiest solution. Use diodes rated for at...
  2. crutschow

    [Solved] Trying to drive a MOSFET with a potentiometer leads to dead short

    I know of no discrete MOSFET that has that characteristic without a substrate diode requiring a connection (normally to the source). There may be some (I know of none) that add an external connection for the substrate diode but it must be biased with an appropriate voltage to keep it from ever...
  3. crutschow

    DC voltage reduction circuit needed

    What's the maximum current at 20Vdc?
  4. crutschow

    [Solved] Trying to drive a MOSFET with a potentiometer leads to dead short

    It is for a P-MOSFET.
  5. crutschow

    [Solved] Trying to drive a MOSFET with a potentiometer leads to dead short

    You are. As danadak noted, the MOSFET is connected backwards. Note the direction of the parasitic substrate diode between source and drain that all MOSFETs have. It's forward biased in you diagram, so provides the near dead short you noted.
  6. crutschow

    LR circuit for PWM Input

    The mechanical analogy of inductance is inertia. The inductance tries to keep the current flowing in the same direction until the inductive stored energy is dissipated. That can cause the voltage across the inductor to reverse, but that just serves to slow down the current, not reverse it.
  7. crutschow

    LR circuit for PWM Input

    You have a common misconception about ground. Ground/common is just the usual name for a node in the circuit that is used as a 0V reference point for all the other circuit voltages (since all voltages are referenced between two nodes). It has no other special characteristic. Obviously no current...
  8. crutschow

    LR circuit for PWM Input

    And my question is, why do you think it would reverse? What do you understand about inductance and how inductors behave, that would lead you to think the current would reverse in your circuit? It would need a voltage source in the reverse direction to reverse the current. That can occur in an...
  9. crutschow

    D Cell Rechargeable pack?

    There are NiMh D-cells available from several different suppliers on Amazon.
  10. crutschow

    Help request: Project measuring the absorbed current

    This is a nit, but you can't "absorb" current, it just flows through the device.
  11. crutschow

    D Cell Rechargeable pack?

    Deleted
  12. crutschow

    D Cell Rechargeable pack?

    That can overcharge the batteries, with possible battery overheating and damage, if the charging is not closely monitored. Better to have a charging circuit that monitors the charging and reduces the charge current when the battery is fully charged.
  13. crutschow

    What incandescent lamp wattage to buy for PSU troubleshooting ?

    Assuming the PSU takes 200W, then its normal operating current is about 200W/240V = .83A, so the bulb would have to be quite large to carry that amount of current without significant voltage drop (likely at least 500W of incandescent bulbs).
  14. crutschow

    D Cell Rechargeable pack?

    Since 4 D-cells require about 6V for charging, you would need to have a boost converter to charge them from a standard 5V USB source. You also would need a charge controller to stop the charge when the battery is full. I doubt you will find a kit for that. It likely would be much easier to use...
  15. crutschow

    What incandescent lamp wattage to buy for PSU troubleshooting ?

    So you want to put this lamp in series with the input power connection?
  16. crutschow

    Will get pulsating DC on a transformer's secondary if I apply pulsating DC to it's primary?

    In summary, if you want 700Adc, then you will need to rectify the 700Aac to get the DC. I have a circuit using MOSFETs in a bridge to reduce the dissipation as compared to Schottky rectifiers, but it would require several MOSFETs in each leg of the bridge to handle that much current. If you...
  17. crutschow

    Need a countdown controller for plug, that needs not button pushing!

    I think a timer such as this, will do what you want. Unfortunately it's not plug-in.
  18. crutschow

    D Cell Rechargeable pack?

    The LED version should last a very long time with 4 D-cells. If you want rechargeable, why not just use 4 NiMh D-cells, and take them out for the infrequent recharge using a standard NiMh recharger.
  19. crutschow

    Weird coil latching problem

    A mistake seldom done more than once. :rolleyes:
  20. crutschow

    Weird coil latching problem

    What is causing the AC to be unstable? What is the source of the AC?
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