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  1. hevans1944

    HOW TO ID-- A 12 VOLT ZENER DIODE --ONE WATT --

    He may have been referring to a comment I made in post #30: Which was a comment on a previous post by @Audioguru: I don't think either of us intended to "bash" @Zendiode or denigrate Third World Countries, but perhaps @ZENDODE was neither amused nor edified (the ostensible purpose of forums...
  2. hevans1944

    HOW TO ID-- A 12 VOLT ZENER DIODE --ONE WATT --

    The circuit suggested by @Audioguru is essentially the same as Figure 21 in section 8.3.10 of this Texas Instruments datasheet, except scaled for operation at a higher output voltage. This particular datasheet has a lot of application circuit schematics, but like most such schematics, it is...
  3. hevans1944

    HOW TO ID-- A 12 VOLT ZENER DIODE --ONE WATT --

    Power inverters are complicated and can be dangerous for amateurs to construct. Everything about the circuit depends on how you specify its operation. Simply saying "I want to convert 12 V DC to 240 V AC" is NOT enough to define and select a circuit that will do that. Have you looked at the...
  4. hevans1944

    HOW TO ID-- A 12 VOLT ZENER DIODE --ONE WATT --

    Amen to using a SMART charger. And a big thank you for identifying the battery. But this is a DIYer trying to cobble together something for his own amusement and edification. I believe you do learn something by "letting the smoke out" of a few things. First, you learn that can be an expensive...
  5. hevans1944

    HOW TO ID-- A 12 VOLT ZENER DIODE --ONE WATT --

    Steve will probably have something to say about this. Short answer: you are doing this all wrong. The resistor is placed in series with the diode (as you show in your photos), but then the free end of the resistor and the free end of the diode MUST BOTH be connected to the battery terminals...
  6. hevans1944

    HOW TO ID-- A 12 VOLT ZENER DIODE --ONE WATT --

    I am not sure I can properly "teach" a 70 year old codger about zener diodes. Not even with videos showing happy electrons marching around the circuit. You need to get some basic concepts nailed down, such as Ohm's Law and Kirchoff's current and voltage laws and how to use them to analyze...
  7. hevans1944

    HOW TO ID-- A 12 VOLT ZENER DIODE --ONE WATT --

    Try looking at the diodes on this page. They are ALL 1W zener diodes and they are ALL the same physical size.. However, the amount of power a zener diode dissipates depends on the product of the zener voltage and the current you allow to flow through the zener. For the simple circuit using a...
  8. hevans1944

    Gunn Diode

    I have been almost completely un-involved with microwaves, except for a brief stint in the Air Force learning to service and repair a Ku band (16 - 17 GHz) dual radar system, and then later (very briefly) at 70 GHz for line-of-sight propagation studies. It's a fascinating world, frequencies...
  9. hevans1944

    TENMA 21-147A

    Thank you for sharing.
  10. hevans1944

    Timed Arduino, Solar Panel, Battery & 12V Pump HELP

    Hmm. Well here it is Friday already in the States. And you still have no clue how to throw the pump, the Arduino, and the 18650 Li-Ion batteries together in a package that will make it through airport security? Or is it just the batteries you want to carry on board or place in the baggage...
  11. hevans1944

    Gunn Diode

    The image you uploaded is from this Wikipedia page. It is a Russian Gunn diode and may be available as surplus on eBay. It must be mounted in a tuned microwave cavity to produce microwave oscillations. Because it is a negative differential resistance device, it can self-oscillate to...
  12. hevans1944

    Any tips on using these crimps?

    These crimp terminals are mounted on a reel strip intended to feed and position (that's what the holes are for between terminals attached to the reel strip) each terminal for automatic crimping and subsequent separation from the strip by a shear cutter... all at a speed faster than the eye can...
  13. hevans1944

    ECG, IRF, 2N Transistor

    You really need to give some thought to what you ask Google to find. For example if your class assignment is to build an amplifier from semiconductor components, ask yourself what kind of amplifier ir should be, and what kind of signals it should amplify. What will the signal input amplitude be...
  14. hevans1944

    Headphone diagnostic

    You don't own a multimeter? That is like trying to do carpentry without a tape measure. Buy one and all will soon be revealed.
  15. hevans1944

    ECG, IRF, 2N Transistor

    Can we avoid going on a snipe hunt here? Haven't used snipe components for amplifiers in ages, although I do have a stash of SN74xxx devices that might qualify.
  16. hevans1944

    Dead Lithium Ion Batteries

    Yeah, I'm with you, I never throw anything away that is presumed dead until I am dead sure it is dead and cannot be revived. I make two exceptions: (1) Alkaline dry cells that are "dead" will go in the trash if the cell voltage drops below one volt; (2) Nickel cadmium or NiCd cells I presume are...
  17. hevans1944

    Circuit that sends 1 pulse when input goes high, 2 pulses when input goes low

    I have GOT to get one of those! My beloved freshman BASIC, circa nineteen sixty-something, compiled and downloaded into a PIC with some assembly thrown in for flavor... what's not to like? It's like being back in the 1970s, but with microprocessors on steroids slimmed down to just eight pins and...
  18. hevans1944

    Circuit that sends 1 pulse when input goes high, 2 pulses when input goes low

    I don't think I am allowed by Florida law to design it for him. That would be "practicing engineering" without a license. Can maybe offer guidance and suggestions...
  19. hevans1944

    Circuit that sends 1 pulse when input goes high, 2 pulses when input goes low

    Could you sketch and photograph a circuit diagram of how the senders are selected? Is there a single relay with SPDT contacts that select one sender when the relay is de-actuated and the other sender when the relay is actuated? That seems simple enough to do with a toggle switch to turn the...
  20. hevans1944

    EEG Question on Getting Data to Computer

    I know you will have a lot of fun with your project, and I certainly don't want to discourage you, but working with microvolt signals in the "wild" in a "floating" environment (for safety) is not easy. Ideally, your scalp electrodes would only pick up signals related to brain-wave activity...
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