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  1. BobK

    18650 power supply

    More important is the "C" rating of the battery. Quadcopter batteries are designed to discharge over a relatively short period of time. Unless you have one that will fly for hours on a charge. Bob
  2. BobK

    It’s time for consumer Electronics Manufacturers to label their transformers!

    The manufacturer of the wall wart is often not the manufacturer of the device it is shopped with. Bob
  3. BobK

    Powering an AC induction motor with a function generator and an audio amp.

    What do you not understand about “preserves?” For a transformer, the power out is the same as the power in. As duke indicated, you get five times the voltage and one fifth the current. Miltiply them together and you can see that the power is the same. Bob
  4. BobK

    Powering an AC induction motor with a function generator and an audio amp.

    No, a transformer preserves the power by raising the voltage and lowering the current, ore vice versa. Bob
  5. BobK

    LEDs powered from AAA battery

    You can also get the charger on amazon. This is the one I use, charges 5 batteries at a time. https://www.amazon.com/Quadpro-Hubsan-Battery-Charger-Quadcopter/dp/B00V5TV216/ref=sr_1_1?ie=UTF8&qid=1517500804&sr=8-1&keywords=quadpro+lipo+charger Bob
  6. BobK

    Powering an AC induction motor with a function generator and an audio amp.

    An amp capable of 500W into 8 Ohms would give you 90V RMS. Seems a bit extreme to run a 40W fan. An amp capable of 40W would output 18V. Coupled with a 5:1 transformer, you would get 90V. Not sure what the effect of the lower frequency would be. Bob
  7. BobK

    LEDs powered from AAA battery

    OK, so you do probably want something like 20mA for each LED. And you presumably want white, which require over 3V. I would go with a small LiPo battery like these: Small LiPo battery I am using these same batteries for some LED strips and I am very happy with them. And they are...
  8. BobK

    LEDs powered from AAA battery

    What do you expect to do with these three ligths. Are they expected to give out significant light (like a flashlight) or just be visible (like an On indicator?) If the latter, under what lightng conditions? For normal indoor lihting, a modern high-efficiency LED can be run at 1 mA. Bob
  9. BobK

    DC-DC converter 24-36 in, 40-60V out @ upto 40A.

    A 40A converter is not trivial. Adding another 12V battery would likely be less expensive, more efficient, and increase, rather than decrease your capacity. Bob
  10. BobK

    LEDs powered from AAA battery

    It boosts the voltage from a 1.5V cell to enough to run LEDs. Most LEDs require about 2V or more. Bob
  11. BobK

    LEDs powered from AAA battery

    You would most likely need some kind of boost converter to run them off a single AAA. Look up "Joule thief". You can run them without a converter from a CR2032 coin cell, which is 3V. Bob
  12. BobK

    Electret Microphone Help

    If you are talking about the inexpensive 433MHz transmitters and receivers you can buy on Ebay, the answer is definitely not. Those modules transmit a bitstream of serial data, not an analog signal. Bob
  13. BobK

    Electret Microphone Help

    An electret needs a gain of about 200 before you get a signal strong enough to use as the input to an audio power amp. That circuit is called a microphone preamplifier. Bob
  14. BobK

    What is up with this?

    I think the statement that you want a lower Rds(on) for higher currents is correct. What was incorrect in the statement is that it is because of power dissipation. The power dissipation will be the same for any MOSFET that is regulating a constant current at a given supply voltage. A smaller...
  15. BobK

    Amplifier project

    I resemble that remark! Bob
  16. BobK

    What is up with this?

    The Rds(on) would limit the current it could source, perhaps? Or at least the compliance voltage range? Bob
  17. BobK

    Amplifier project

    I have never built one with significant power (like typically < 1W.) Get the urge to do so every now and then, and then I look at Ebay. sigh... Bob
  18. BobK

    Charge Batteries in Series

    They are probably charged in series. If the batteries are identical and in the same condition, it will sort of work. A balancing charger can charge batteries in series while treating each one individually by bypassing it once it becomes fully charged. This is typically done with LiPo...
  19. BobK

    Detecting an active low signal

    Okay, I see, you are trying to do it by modifying only the connector. I envisioned the other connections on the boards. Bob
  20. BobK

    Detecting an active low signal

    Why do you need 2 pins? On the detector side, connect the one free pin to Vcc through a pullup and the uC input. On the other side, connect that pin to ground. Bob
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