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  1. (*steve*)

    Mosfets and second(ary) breakdown

    Anyone who's interested probably scratched their head at this. Zener voltage decreases with temperature, but avalanche voltage has a positive temperature coefficient. The trick is that whilst avalanche voltage does have a positive tempco, at elevated temperatures this trend is reversed. Hmm...
  2. (*steve*)

    Mosfets and second(ary) breakdown

    The references I've found say that it is *more* of an issue with modern mosfets.
  3. (*steve*)

    Challenging task

    Let's assume you're talking about a microcontroller. The easiest method may be too toggle some output pin. Move this code around until you find the point at which the output no longer toggles. Whatever precedes this is the problem. Edit: I was assuming a totally different problem.
  4. (*steve*)

    Mosfets and second(ary) breakdown

    A note to those who already know this... I've just learned this and I thought it was interesting enough to post -- I'm not claiming to have discovered it! A common statement is that "mosfets are not subject to secondary breakdown". It's one I've made multiple times and is one that appears in...
  5. (*steve*)

    Need recommendation for rheostat or potentiometer

    So, have you considered my suggestion of mechanically restricting the airflow? Another option is to vector part of the airflow where it won't do any harm and won't provide thrust. It's probably easier to do the former.
  6. (*steve*)

    Anyone has Datasheet of VT542SRI-4 ?

    Is the spacing clearly something other than 1/10 inch?
  7. (*steve*)

    Anyone has Datasheet of VT542SRI-4 ?

    The spacing is more important than the size of the hole. I've looked, but I can't find the datasheet.
  8. (*steve*)

    Atx modify help me

    You need to find a power supply where the 12V rail is regulated and modify the feedback loop to set it to the required voltage.
  9. (*steve*)

    Red Green Led 2 Leg

    No, I mean the 4 diodes shown on that circuit need at be Schottky diodes. Having them rated for maybe twice the max input voltage would be safe. In this case 20V or more would be fine.
  10. (*steve*)

    Red Green Led 2 Leg

    The resistor can be on either side of the LED, it doesn't matter. The following circuit will limit the LED current to 10mA for an input voltage between +/-6V and probably +/-30V. To operate correctly at 6V the diodes should be Schottky diodes. Sorry about the quality. Edit: transistors can...
  11. (*steve*)

    Red Green Led 2 Leg

    Yes it will. The brightness will vary, but the LED will be safe. Does the variation in brightness concern you?
  12. (*steve*)

    Does this capacitor look bad to you?

    Yeah, replacement seems to be the best option. I thought it may have been a shadow, but after I looked in more detail, it clearly isn't. I am curious if there are any other signs of leakage.
  13. (*steve*)

    Red Green Led 2 Leg

    Yes, we know
  14. (*steve*)

    Need recommendation for rheostat or potentiometer

    An astable multivibrator can be used to create a simple PWM circuit. You can also use a power transistor and a few simple components to make a simple linear regulator to limit the voltage to the fan. You could also mehanically limit the airflow through the fan.
  15. (*steve*)

    Red Green Led 2 Leg

    Place a 470Ω resistor in series with the LED.
  16. (*steve*)

    Mosfets in parallel

    The mosfets need to be quite similar, but not actually matched (in most cases where you are switching). The important thing is that the mosfets have separate gate resistors to allow both of the mosfets to switch simultaneously even if they have slightly different Vgs(th) or Vgs/Id curves.
  17. (*steve*)

    Anyone has Datasheet of VT542SRI-4 ?

    Can't you just measure it?
  18. (*steve*)

    Volatile and interrupts

    It really depends on whether or not you want to chase down weird bugs. Be aware though that the volatile keyword disables some optimization, so you may need to carefully consider where and when you want to get the current value. For example if the variable conntrols the color of 100 LEDs and...
  19. (*steve*)

    Does this capacitor look bad to you?

    Well... That discoloration on the end looks unusual. Can you take a photo of the end of the caps that are discoloured?
  20. (*steve*)

    Simulators?

    Ltspice
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