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  1. Alec_t

    Woo-Woo Powerful changing magnetic field generator. Can influence human cells activity ?

    Both. An EM pulse field is superimposed on a static field.
  2. Alec_t

    Forum Category Feedback

    I don't think specific Homework problems would be regarded by a student as a General topic. I think Homeork should be a separate category, and that there should be references out from the other categories to the Homework category. As it stands, a student given an assignment involving, say...
  3. Alec_t

    Woo-Woo Powerful changing magnetic field generator. Can influence human cells activity ?

    Externally applied EM fields obviousy can affect body cells. How else would NMR scans work? What do you hope to achieve by spinning a magnet?
  4. Alec_t

    Reduce amperage without reducing voltage. Diodes? [Noob]

    ..... or run the motor from a 6V supply for safety (although that's not what you want).
  5. Alec_t

    Can you make my 12v LED light up?

    C1 is ceramic or plastic film type. Voltage >=25V (or unspecified) is fine. Something like this for the trimmer, perhaps. 0.5W or less.
  6. Alec_t

    DC-DC converter 24-36 in, 40-60V out @ upto 40A.

    Welcome to EP! I can't see any advantage in using a split-pi circuit, which is essentially a buck-boost converter. Your required output voltage is always above the input voltage, so a boost converter seems to be all you need. Converter design (of whatever flavour) is far from trivial. Will your...
  7. Alec_t

    Pulse Width Modulation

    Most DMMs won't give accurate readings of a pulsed voltage (PWM).
  8. Alec_t

    Can you make my 12v LED light up?

    Here's the revised circuit. Note that R1 is now 47k, C1 is now only 100nF and positioned differently. The 100k trimpot sets the green LED cut-in point.
  9. Alec_t

    Can you make my 12v LED light up?

    No voltage is present at the PWM-in connection, but with the present circuit the smoothing capacitor C1 does suck 1/2 mA or so of juice from that input (hence from the controller). I'll do a re-design of the circuit input to reduce that current and incorporate a sensitivity adjustment for the...
  10. Alec_t

    Can you make my 12v LED light up?

    If the PWM signal oscillates between 5V and 0V it will take about twice the duty cycle to turn on the green LED than if the oscillation is between 10V and 0V. Your meter 'sees' a sort of average. With the circuit posted the running average is actually stored on C1. An average of at least 0.6V is...
  11. Alec_t

    Can you make my 12v LED light up?

    Yes, 'floating' means no input connection. R5 should be 10 kilOhms, not 10 Ohms! If all your other measurements are Ohms rather than kilOhms then there are several short circuits around Q1 or else you have a bunch of incorrect resistors. Looks like Q1 is dead, from the reading for its...
  12. Alec_t

    Help with fence charger schematic

    One example would be Irfanview. It can open and process all sorts of files.
  13. Alec_t

    Charge Batteries in Series

    In other words, you need a special charger to charge batteries in series; not a standard 12V charger.
  14. Alec_t

    Burglar alarm.

    Post the schematic, if you have one.
  15. Alec_t

    Charge Batteries in Series

    No. Charge them individually.
  16. Alec_t

    Thermal fuse help needed..

    Then the fuse is a DC one.
  17. Alec_t

    Bluetooth Mic

    Have you considered an off-the-shelf solution; a radio mic such as is used by actors/performers on stage? Some may not be Bluetooth, but is that important? I doubt you'll be able to build one yourself cheaper than the numerous offerings on Ebay etc.
  18. Alec_t

    Can you make my 12v LED light up?

    Ok. It's a mystery why Q1 would get hot. With the green LED disconnected, PWM input floating and the circuit un-powered, measure the resistance 1) of R5, 2) from each of the Q1 legs (b,c,e) to the +12V rail, 3) from each of the Q1 legs to ground. For each measurement, measure using the meter...
  19. Alec_t

    Pre-Scaling a squarewave. Output weird.

    Agree with AK. Trigger point (start of the ringing on the 4040 output trace) coincides with clock falling edge only.
  20. Alec_t

    Can you make my 12v LED light up?

    I'm at a loss to explain the results you're getting. Even reversing the power supply to the circuit or swapping the connections to the legs of Q2 can't drive enough current through Q2 to cause significant heating. The fact that connecting the PWM input to 12V turns off the green LED suggests you...
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