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  1. hevans1944

    Voltage Drop across NPN BJT C&E?

    Following Colin's remark, I Googled several variants of the "9018" part number. Everything I found that was a transistor was an NPN epitaxial transistor, and they were all probably derivatives of the original Fairchild part. Epitaxy, the growth of thin layers one on top of the other, is how my...
  2. hevans1944

    Old Wagner electric 1 HP 1 phase Type RA motor

    Amazing, hell! They really knew how to build good motors back then: good steel ball or roller bearings, lots of good silicon steel in the magnetics (rotor and stator), heavy-gauge OFHC (oxygen free high conductivity) copper in the windings (probably), heavy-duty insulation on the copper, and a...
  3. hevans1944

    Old Wagner electric 1 HP 1 phase Type RA motor

    They are called zerk fittings, not zerts. You use them with a motor-bearing grease, not oil. The zerk fitting has a simple ball-and-spring one-way valve that allows you to insert grease through it, and subsequently through the motor bearings, under moderate pressure, displacing the old grease...
  4. hevans1944

    Was I dreaming (fast PCB etching)

    One manufacturer I used a long time ago electroplated first copper and then lead-tin solder through a photolithographic mask to define the traces and make plated-through holes. Board was originally clad with very thin copper on both sides and then drilled. They used electroless copper deposition...
  5. hevans1944

    please can someone help me out with this:-

    Try reading this Googled article. Have you met my good friend, Google, yet?
  6. hevans1944

    glucometer

    A non-invasive blood-sugar measurement is a tough problem to solve. See this Wikipedia article. There is, however, one company who sells a device that claims to have solved the problem using multiple sensor technologies and a proprietary algorithm. The sensor head is clipped to an ear lobe and...
  7. hevans1944

    Voltage Drop across NPN BJT C&E?

    We are talking about a specific, ancient (November 2002), epitaxial-constructed transistor, the Fairchild SS9018, as linked to by the OP. This particular transistor has an hfe range of 28 to 198, sorted into six bins. It doesn't even make it up to 200 on its best day, Colin. Try reading the...
  8. hevans1944

    Winter down under time

    Two Coleman lanterns have been our go-to camping lights for many years, and one of our sources for emergency light at home. I always keep a few spare mantles in the carrying cases we bought for the lanterns, along with a can or two of Coleman fuel and a spare lantern generator. Not only do they...
  9. hevans1944

    Capacitor confusion

    Energy stored in a capacitor is 1/2 CV^2 = (0.5) (18) (3900 x 10^-6) (400)^2 = 5616 joules. Enough to kill you. Capacitors is parallel add their capacitance. Voltage rating of the parallel combination is that of the lowest voltage rated capacitor, or 20 V in your example. Makes no difference...
  10. hevans1944

    Questions for fixing electric piano

    Please do.
  11. hevans1944

    Winter down under time

    Yeah, snow. I am hoping to avoid that real soon now. And rethinking this, forget about insulating the can: we want the heat to be be dissipated to the environment, not trapped inside the can. I wonder if there isn't some luminescent substance that magically converts infrared energy into visible...
  12. hevans1944

    Voltage Drop across NPN BJT C&E?

    MOSFETs can be vulnerable to gate oxide punch-through because that insulating layer between gate and body channel is very thin. That is why @BobK said to always have some high-valued resistor between the gate and source pins to drain off static build-up. You can, of course, use less resistance...
  13. hevans1944

    Charging/Discharging circuit for multiple 18650 batteries

    Hide the power bank inside your project box?
  14. hevans1944

    Winter down under time

    Even filling the can with water, and insulating the outside, would help. No snow necessary, just dump the water and re-fill the can after the water gets hot. My boss at my former employer bought one of those Peltier thingys that generate electricity, just to "experiment" with and perhaps...
  15. hevans1944

    Modulating Hydraulics

    You would need to signal-condition the sensor output and then use that to digitally modulate a wireless transmitter co-located with the sensor. The "easiest" solution might be an Arduino Uno with an XBee Bluetooth shield communicating with another similarly equipped Arduino with Bluetooth...
  16. hevans1944

    Temperature compensation for Geiger tube

    That would depend on whether or not you can find a relationship between humidty and GM pulse rate, or between temperature and GM pulse rate using a known radiation calibration source placed at a fixed distance from the entrance aperture of a Geiger-Muller tube. The energies of the radiation to...
  17. hevans1944

    Voltage Drop across NPN BJT C&E?

    It isn't the base that saturates. It is the collector-emitter circuit. Saturation occurs when the depletion layer at the base-collector junction has been reduced to zero by forward biasing the base-emitter junction. The collector current increases and the voltage between the collector and...
  18. hevans1944

    Temperature compensation for Geiger tube

    Show us the calculation without a temperature variable.
  19. hevans1944

    Automatic ranging current sensing

    I have managed (so far... it isn't midnight yet!) to resist the offer by Circuits Specialists for a spiffy cell-phone enabled Mooshimeter digital VOM with up to 24-bit resolution and decent accuracy for a measly $120, less a substantial discount because today is IEEE Day. :D I wonder if I can...
  20. hevans1944

    Steel work bench

    It could possibly have tripped a circuit breaker off when the lamp support became "hot" and most certainly would have caused a GFCI (Ground Fault Circuit Interrupter) to trip. Grounds, especially good ones, are what get people electrocuted. Keep your body away from grounded objects. Keep one...
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