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  1. (*steve*)

    LED Christmas lights gone dim

    Do they run from line voltage or something a lot lower? If they run from a high voltage it may be that it is actually just one string with a simple single point failure
  2. (*steve*)

    micro I/o lines

    Unless something else pulls it (harder) to ground. The output takes the state you set it unless the pull up resistor has such a low value that the microcontroller can't pull it low. in addition, when you set the output to a low state current will flow through the resistor. Yes. If the...
  3. (*steve*)

    Why would sections of an RGB LED string freeze animating after 30 mins?

    Try injecting power at the far end and see if it improves things.
  4. (*steve*)

    Good Resource For Learning Bjt Transistors And Amplifier

    Wallwart's only teach the black art of induction.
  5. (*steve*)

    Good Resource For Learning Bjt Transistors And Amplifier

    Fair enough.
  6. (*steve*)

    Good Resource For Learning Bjt Transistors And Amplifier

    I agree with the above two posts. I guess I see "base current controls collector current" as a useful simplification when applied to a very common first use of a transistor. If this is as far as someone goes it will be sufficient. I agree that if you teach the diode first (presumably going...
  7. (*steve*)

    Good Resource For Learning Bjt Transistors And Amplifier

    I guess you could also start with Vbe controlling Ic* but you then have to explain that you can very rarely directly control Vbe. I would prefer to go the other way. And you didn't address the terrible problems of teaching that false and misleading Newtonian physics which is apparently useful...
  8. (*steve*)

    transistor for open-drain / open-collector 25kHz PWM

    Yeah, that's a lot more informative.
  9. (*steve*)

    Good Resource For Learning Bjt Transistors And Amplifier

    Do we teach F = MA? We know it's wrong. As you said, everything is a simplification. Base current controlling collector current is a gross simplification because it both puts the cart before the horse and because it assumes certain facts about the load. However even within those constraints...
  10. (*steve*)

    transistor for open-drain / open-collector 25kHz PWM

    That should be fine for 25kHz. At a minimum you'll be able to check that with the fan connected an appropriate signal appears at the PWM input. If you don't see a signal, try connecting your own pull-up resistor (1k should be fine). As I read the version 1.2 specs, it doesn't appear obvious...
  11. (*steve*)

    Problem with diy audio mixer - high frequency sound

    You could improve it by using shielded cabling, and connecting the variable resistor as a potentiometer rather than a rheostat, and by adding a buffer amplifier to the output. I would recommend an emitter follower.
  12. (*steve*)

    transistor for open-drain / open-collector 25kHz PWM

    This looks like the general specs.
  13. (*steve*)

    transistor for open-drain / open-collector 25kHz PWM

    OK, so it's not actually the fan you're powering, just supplying a signal to it. Assuming the fan can accept a 25kHz signal, you should be good to go. Have you looked at the signal on an oscilloscope?
  14. (*steve*)

    Standard Incandescent Bulb Salvaging

    Acid core solder is probably fine for plumbers, but you should never use it for electronics. And I hope you understand the difference between an acid and a base. On that matter, have you seen the damage that leaking batteries can do to electronics? Would you intentionally spread this stuff...
  15. (*steve*)

    transistor for open-drain / open-collector 25kHz PWM

    Ok, now explain what the load is and where it is connected. What current does the load draw? Is it inductive?
  16. (*steve*)

    Problem with diy audio mixer - high frequency sound

    If your ears hurt, either turn down the volume or get a pair of headphones that don't squeeze your ears so hard (or both). Your circuit is poor for a number of reasons, but given your construction it would be hard to fix. If it kinda works, it is probably better than nothing.
  17. (*steve*)

    Good Resource For Learning Bjt Transistors And Amplifier

    There are two (and probably more -- but let me simplify it to two) ways of teaching a topic like this. In the first, you start at the deepest, most fundamental level and build up to a level where you are talking about the broader concept. This approach has advantages where you know the deepest...
  18. (*steve*)

    transistor for open-drain / open-collector 25kHz PWM

    You'll need to show us your circuit for us to make any comment as to why the circuit works for a LED but not a fan. I suspect the fan draws more than 8mA. The actual switching speed depends on a number of factors which are interdependent in a typical circuit. There factors include the gate...
  19. (*steve*)

    40 Hz LED

    A pair of 2N2222's configured as an astable multivibrator would be an option I'd consider. Also I'm a bit uncomfortable with my quick experiment being called a major research project :-)
  20. (*steve*)

    Hello, Welcome! (Introduce yourself)

    Yeah, hang around, ask questions, build things. You'll learn stuff faster than you think :-)
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