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  1. hevans1944

    Random digital potentiometer driving

    There are many ways to accomplish what you are asking, but as others have stated, we need to know exactly WTF you are REALLY trying to DO. Being coy about this is not going to help you. Why? Digital potentiometers are practically begging for microprocessor or microcontroller control. That would...
  2. hevans1944

    Coronavirus transmission prevention device.

    Yeah, so what? Consensus only demonstrates that sheeple will all march over the cliff along with the lemmings. Well, lemmings are "smarter" than that: It is an urban myth, fraudulently popularized by Disney filmmakers, that lemmings commit suicide en masse by jumping off cliffs. But the meme...
  3. hevans1944

    Coronavirus transmission prevention device.

    As a "Air Force Brats" (children whose parent or parents serve in the Air Force), my brother and I moved around a LOT. We also got vaccinated a LOT. I had to have several smallpox vaccination "jabs" because the expected reaction did not occur. One finally did yield the expected results: an...
  4. hevans1944

    Transistor as a switch

    Gee... where's a Moderator when ya need one? The OP, @champ1, hasn't been seen here since April 26, whereas the original post was made earlier that same day. I won't say this was a "drive by" poster just looking for a quick answer and then moving on... but surely the conversation from all the...
  5. hevans1944

    5V Computer Fan - easy way to reduce speed?

    Reducing the effective voltage to the fan motor, whether by PWM or using a variable output power supply, may not work if the fan is driven by a brushless motor that operates at 5V and draws only 0.15A or 150 milliamperes. This type of motor requires electronics to switch and route its supply...
  6. hevans1944

    Coronavirus transmission prevention device.

    Just visited this link (again) to see how many people have died while infected with the novel corona virus or COVID19. There have been several virus mutations since the COVID pandemic started and two types of "vaccines" were developed. One, based on messenger RNA (mRNA), and another based on a...
  7. hevans1944

    Wiring question on electric bike

    I agree with @Bluejets. If a larger image file with more resolution is necessary to communicate a concept or an idea, there are several solutions available. My favorite is an email attachment, but that removes the higher-resolution image from discussion in the Electronics Point forums. And you...
  8. hevans1944

    Wiring question on electric bike

    As MANY others here have stated: reduce the size of the image you are uploading until you no longer receive error messages. This sometimes happens to me because almost all of my image SOURCES are high-resolution. Always check the file size of the image you want to upload to this forum. If it...
  9. hevans1944

    Transistor as a switch

    I have a quibble regarding the simulation model and some of the graphical responses depicted here. Two of the graphs depict a sharp change in the transfer function, somewhere in the vicinity of 0.8 volts at the emitter-base junction. This sharp transition point on the graph does not occur with...
  10. hevans1944

    Splatter in relay

    Hmmm. Do you get this from the same store that sells headlight fluid and muffler bearings? Oh, wait! You probably meant something like Dow Corning Vacuum Grease or perhaps the heat-sink compound used between a semiconductor case and its heat sink...
  11. hevans1944

    Transistor as a switch

    Yes, the discipline required for success in almost any endeavor (including the practical applications of electricity and electronics) relies on the practitioner, and his or her knowledge of working theory being robust, trustworthy, safe, and effective. This forum does promote those four...
  12. hevans1944

    AC audio signal superimposed on to DC question

    Yes, but the OP may not understand the significance of the superposition principle. It did not seem intuitively obvious to me, when I first encountered it, slightly more than midway through the previous century. It later turned out to be of inestimable value when performing circuit analysis and...
  13. hevans1944

    AC audio signal superimposed on to DC question

    In a word: superposition. In a linear circuit, voltages from different sources, AC or DC or both, can be algebraically "added" or superimposed. Later, circuits can be used to "restore" the DC levels "lost" as a result of AC coupling. In the case of a biased transistor, this means that the DC...
  14. hevans1944

    Transistor as a switch

    Yeah. Everybody that posts a question here should first demonstrate a working knowledge of Ohm's Law, which states that the current in a circuit is proportional to the voltage that created the current and inversely proportional to the resistance in the circuit through which the current occurred...
  15. hevans1944

    Transistor as a switch

    What you have done is jump-start a veeery old thread that attempted to discuss how a transistor works. The thread became a tug-of-war between those who said the "transistor is a (base) current-controlled device" and the "transistor is a (base-to-emitter) voltage-controlled device. Nothing was...
  16. hevans1944

    Requesting more Greek letters

    The forum appears to default to Arial type-font, with sizes available varying from 1 to 7as shown here. The default size seems to be 4. I am not a big fan of sans serif fonts, so I usually choose Times New Roman for serious writing so as to easily distinguish between 1, l, and I like this: 1, l...
  17. hevans1944

    Requesting more Greek letters

    The symbols we currently have (Ω, μ, and ±) are certainly useful in technical discussions, but I keep a Microsoft Windows symbol page (charmap.exe) open to select the "special characters" that I need to insert in text from time to time. Users of Linux and iOS may have similar resources...
  18. hevans1944

    Detect 5v button push on separate system

    It isn't explicitly stated that the System B must "turn on if System A 5V is present" and "stay turned on (latched) even if the 5V from System A goes away." In fact, I believe that System B is intended to be active if and only if System A is simultaneously active. Perhaps the OP can clarify this.
  19. hevans1944

    Detect 5v button push on separate system

    I have used photocouplers many times to routinely galvanically isolate an output signal intended to control something in the "real world." It should be fine for your purposes, provided you pay attention to its limitations of speed, voltage, and current as described in the datasheet. An infrared...
  20. hevans1944

    Table radio makes loud popping sound when powered on

    Just because it has a famous name brand, and costs big bux, doesn't mean it has a good design. The "pop" is probably the audio output stage charging up a capacitor coupling the audio to the loudspeaker. The capacitor may be defective, or this may be "normal" operation for the circuit. A lot of...
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