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  1. (*steve*)

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

    Humor me. Just try connecting the microcontroller output to the PWM input. You can leave the 300Ω resistor there if you want to.
  2. (*steve*)

    Schematic to breadboard

    Well, the resistors R1 and TM1 are in series with the power connected to the circuit of T2 and there is also an inductor in series between them and the collector of T1. It isn't correct to say they set the voltage for these transistors, it's a bit more complex than that. I also don't like the...
  3. (*steve*)

    Low Speed Relay

    One obvious thing you'll also need is a method to override it for a short period of time. Without this you can't turn the PC on. It could be as tricky as having the microcontroller turn power on, control the power on signal from the power supply, and wait some time for the fans to come up to...
  4. (*steve*)

    What is the resistance and wattage of this resistor

    It's very hard to tell. But if you have a multimeter you can determine the resistance easily.
  5. (*steve*)

    mains rectified voltage for christmas lights

    Yeah I've seen Christmas lights like that where the resistors drop the bulk of the voltage and dissipate comparatively large amounts of power. :-(
  6. (*steve*)

    mains rectified voltage for christmas lights

    That's DC going to the capacitor. See the 4 diodes?
  7. (*steve*)

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

    True, but the temperature may vary either the output voltage from the power supply or the voltage sensitivity of the assessable LEDs. If either of these only happen at the end of the string then increasing the voltage at the end of the string may be sufficient to keep them working. These...
  8. (*steve*)

    mains rectified voltage for christmas lights

    Not connected to AC either.
  9. (*steve*)

    mains rectified voltage for christmas lights

    My understanding is that some LEDs are made with more bulk silicon which adds an effective series resistance to them. It would be interesting to trace the curves of some of the devices. Maybe something to do with Christmas lights after they're taken down...
  10. (*steve*)

    Newby to this Forum. LOWE HF-225 Reciever!

    I've recently replaced a pair of these batteries in some 30+ year old equipment. I replaced them in both pieces of equipment because it was not much harder than doing just one. They were clearly original equipment, and one still had sufficient voltage to preserve the "non-volatule" RAM. I may...
  11. (*steve*)

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

    What's wrong with connecting a 5V logic signal to a port which expects a 5V logic signal?
  12. (*steve*)

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

    The BS140 can have a very low Vgs(the). This can make the device slow to turn off. The is also no reason to use the MOSFET at all. Just connect the microcontroller output to the fan. If you're really interested you can view the waveform at the gate. If you have a dual channel scope...
  13. (*steve*)

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

    Just to be clear, my suggestion was to also inject power into the far end, i.e., connect both ends to power.
  14. (*steve*)

    24 VAC to 12 VDC

    Rectify, filter, and use a small DC-DC switch mode regulator.
  15. (*steve*)

    Hello, Welcome! (Introduce yourself)

    Welcome khalifa, we hope we can be of assistance to you.
  16. (*steve*)

    Schematic to breadboard

    No, and no. The collectors don't connect to each other so even if one connected to +5v, the other would not. Pins 3 and 4 connect to ground. Pin 7 connects to a capacitor (the other end of which kind to ground). The simple rule is to follow where the lines go. Remember that crossing lines...
  17. (*steve*)

    Newby to this Forum. LOWE HF-225 Reciever!

    Sure if a picture of the battery. If it's about the same size as an AA battery but has wire leads, then it's likely to be a 3.6V non-rechargeable lithium battery. There have a very long lifetime and don't leak. There are two good reasons not to ride them with normal batteries. Replacements...
  18. (*steve*)

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

    Have you tried connecting the microcontroller output directly to the fan? Perhaps leave that gate resistor between them just in case.
  19. (*steve*)

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

    I think it's simply that the pull up in the fan is too weak. Perhaps the fan designer read the older spec that I did and assumed an external pull up? You could try reducing your gate resistor just in case the problem is that it is large enough that the MOSFET switch off time is being affected.
  20. (*steve*)

    TV transmitter - picture slides vertically

    If say the sync pulse at the beginning of each frame is being distorted or removed.
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