Search results

Search Forums New Posts
  1. Alec_t

    Need help designing / understanding this 'circuit'

    A lever-actuated microswitch could do the job without the need for a relay or any electronics.
  2. Alec_t

    Electric Ducted Fan Powered Longboard Help Please!

    Cool, but I would expect a fan (even a ducted one) to be very inefficient compared to direct motor drive of the wheels. Have you done any research on that? Are you set on using a fan despite its inefficiency?
  3. Alec_t

    Any Idea how to solve this question?

    Show us your best efforts so far at this homework and we can give guidance.
  4. Alec_t

    Samsung Battery Thermistor (NTC) type?

    Welcome to EP! Why did you remove the PCBs? They are there to protect the battery from incorrect charging/discharging and are critical safety components to prevent fire/explosion.
  5. Alec_t

    n-mosfet replacement on Qnix lcd monitor

    Nice one. Good to have a happy ending to the story. Which FET did you finally choose?
  6. Alec_t

    Multiples Fans - cooling system for Laptop

    Check the voltage rating marked on the fans. Very likely they're12V fans, so might not be happy/efficient working on 5V from a USB port. You shouldn't need resistors.
  7. Alec_t

    Feeding a square pulsed DC into a transformer's primary winding.

    No. DC doesn't get through the transformer. The secondary winding current will settle down, after an initial displacement from zero, to a square-wave oscillation symmetrical about zero. Like this:-
  8. Alec_t

    Esr Meter Build

    That's way above what the schematic shows. Rather than increase that value it might be easier to slap another resistor (say 1k) in parallel with R7.
  9. Alec_t

    Esr Meter Build

    Not sure what steve would suggest, but did you try the R3 increase as per my post #5?
  10. Alec_t

    n-mosfet replacement on Qnix lcd monitor

    It's impossible to say without knowing the conditions (e.g. frequency, driver impedance) under which the gate is being switched. Looking through various MOSFET datasheets it seems to me that, in general, the lower the gate capacitance/charge the higher the Rds(on) resistance. Which of those...
  11. Alec_t

    n-mosfet replacement on Qnix lcd monitor

    Yes, unfortunately that is possible. Soldering by hand is never going to be as effective as the reflow method used in the original assembly, which would have eliminated any gap. It's also possible that a faulty component elsewhere, or a design error, is causing the FET to pass excessive current...
  12. Alec_t

    Esr Meter Build

    I don't see why not, but I thought changing just one resistor might be simplest. Either method would require re-calibration.
  13. Alec_t

    7404 Hex inverter stuck on 2.5v

    Have you left any of the unused inverter inputs floating? That might produce weird results.
  14. Alec_t

    Esr Meter Build

    Try increasing the value of R3 to ~220k. This will reduce the test voltage, but a side-effect is a change in oscillator frequency, which will require re-calibration of the meter.
  15. Alec_t

    7404 Hex inverter stuck on 2.5v

    Have you checked that with a 'scope? If the output were oscillating and you checked with a DMM, 2.5V would be a reasonable measurement.
  16. Alec_t

    Signal conditioning for 555 circuit

    Here's a variant which should make triggering by the 'every-10s' pulses less likely, even if one occurs fairly soon after an alarm session ends. This uses a .......wait for it........'555 IC :D. The Q1 stage is much as before. When the C1 voltage drops below the 555 Trig threshold the 5555...
  17. Alec_t

    Tablet adapter doesn't turn on

    Looks all right ;)
  18. Alec_t

    Signal conditioning for 555 circuit

    Nice to hear it works! Try reducing R2 to, say, 47k, to shorten the C1 discharge time, then re-adjust the trimmer.
  19. Alec_t

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

    Perhaps this tutorial will help?
  20. Alec_t

    PWM LED THROUGH MOSFET

    Very likely. I agree with BobK.
Top