Search results

Search Forums New Posts
  1. hevans1944

    How Is This RC Circuit Dropping Voltage

    That is correct, but doesn't get you any closer to determining what the AC applied voltage and frequency is since you don't know how much current is allowed in the zener. Certainly. But it is unsafe to do so to provide a low voltage DC from the mains supply. Better to spend a few bux for a...
  2. hevans1944

    Newbie scope question

    Been there, done that, all without ever using (or wanting to use) an oscilloscope. Too easy? Maybe for an auto built in the 1960s or earlier, but lately changing spark plugs and plug wires has become a real PITA, what with engines mounted sideways for front-wheel drive, and half the spark plugs...
  3. hevans1944

    Practical vacuum tube signal generator

    I envy your access to vacuum tube (valve) technology. Except for a few RF power tubes, I gave away my collection of valves years ago to someone who restores vintage radios from the 1920s. IIRC, one of the first audio oscillators I built was a three-stage, RC, phase-shift oscillator that coupled...
  4. hevans1944

    Trying to identify something that resembles a transformer!

    Good idea. Take the time to wire up a standard Edison-base lamp socket so you can swap in incandescent lamps of various wattages. Start small, say, 25 watts or so and work your way up towards 200 to 300 watts. Most of the applied AC line voltage will be dropped across the low-wattage lamps. If...
  5. hevans1944

    Newbie scope question

    You mentioned the Tektronix 475 oscilloscope in your original post... these were fine instruments when new and are available on the used market for very reasonable prices in the $200 to $500 price range. I have purchased two of them (used) over the past thirty years or so and they have given me...
  6. hevans1944

    What is this device called ?

    I think an appropriate name would be Pie-In-The-Sky Energy Harvester or PITSEH cell. These would come in various sizes such as A, AA, AAA, B, C, D, etc. depending on your energy use requirements. Easily carried into the wilderness, the PITSEH would, ideally, be environmentally friendly...
  7. hevans1944

    Carbon monoxide detector signal conditioning

    Well, it is what it is. The choice of sensor must of course consider acquisition cost, but the primary criterion should be the sensor capability. Low cost "sensors" that don't work waste our time and yours. How does your "hot wire sensor" measure up for that? How does the resistance of a coil...
  8. hevans1944

    Newbie scope question

    Auto spark wave forms are high voltage damped oscillations. To view them successfully on the 475 oscilloscope you need a frequency-compensated, high-voltage, attenuation probe, typically insulated with a fluorocarbon liquid insulator. The Tektronix P6015A is the "go to" probe for this purpose...
  9. hevans1944

    Trying to identify something that resembles a transformer!

    Auto-transformers are pretty nifty, especially variable auto-transformers (which your example is not) also known as Variacs™, but those that operate directly from line (mains) voltage can be very dangerous, even lethal, for the newbie to "play" with. Newbies should stay away from any circuits...
  10. hevans1944

    Transmitter to oscilloscope

    Actually, with a conventional cathode ray tube (CRT) that has electrostatic deflection plates, you can. Back in the day... and believe it or not this was waaay before my time... Hams and broadcast engineers would connect their (suitably attenuated) transmitter outputs directly to the vertical...
  11. hevans1944

    Struggling to find a gigabit-speed Transimpedance amplifier for an APD

    I would start with the Analog Devices ADN2880 and see if there is newer technology available.
  12. hevans1944

    Newbie Question Regarding Reed Switches/Sensors

    How do you expect to successfully design anything without specifications? Get a multimeter and measure the motor current and the motor voltage applied by a set of fresh AA dry cells. Make the current measurement with the device spinning normally and the LED illuminated. Then restrain the device...
  13. hevans1944

    when you learnt and become pro, did anything amazing happen?

    Not sure what you mean by that statement about "never see the light of day." It is true that the B-52 fleet has never participated in a nuclear war, but the later versions did participate in the Vietnam war, flying from Guam to bomb Hanoi and "other targets" of opportunity, not necessarily in...
  14. hevans1944

    when you learnt and become pro, did anything amazing happen?

    If I ever get bored in retirement, and get a workbench set up again, maybe I will try to "turn a few tricks on weekends for extra cash." Gotta be careful though... I never did get a Professional Engineer license after graduating college in 1978 because none of my (mostly) Department of Defense...
  15. hevans1944

    capacitor testing for novice please

    Agreed. This conclusion is also supported by the table posted by @caps in his post #11. Nevertheless, I believe it is most useful to test for leakage at the working voltage direct current (WVDC) rating of the capacitor. The one time I rely on a 10 volt leakage test for a 450 WVDC electrolytic...
  16. hevans1944

    capacitor testing for novice please

    A capacitor is constructed by winding into a cylinder two parallel foil sheets, usually aluminum, insulated from each other by a layer of plastic. Conductive leads are then welded to the two aluminum foils and the whole assembly is then potted in plastic. A somewhat different technique is used...
  17. hevans1944

    Measure distance to water surface

    Here is an application note on the HC-SR04 sensor that may be useful in calculating your measurement error. Note that this sensor performs no temperature correction for the velocity of sound. The width of the return echo is a function of distance and is the parameter your microprocessor...
  18. hevans1944

    nano coils

    Your post MNFS. Go troll somewhere else.
  19. hevans1944

    50w rms into 8 ohm load amplifier circuit using single dc power supply

    I must admit that @Audioguru's suggestion to consider using the LM3886 IC is an excellent way to get on with your life. Make sure you provide an adequate heat sink for the IC. OTOH, building from scratch with discrete transistors, resistors, capacitors, and diodes is a great way to learn about...
  20. hevans1944

    50w rms into 8 ohm load amplifier circuit using single dc power supply

    Why? When you are designing an audio amplifier, specifying a single dc power supply severely limits your circuit design options. The sub-woofer is accepting low-frequency alternating current audio signals and producing sound by moving a voice-coil back and forth about a centered position in an...
Top