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  1. hevans1944

    Help needed to replace a relay

    Is that a "crystal can" relay with wire terminations and a 24 VDC coil? Used to be zillions of these on eBay. Look here too.
  2. hevans1944

    This some kind lightbulb or...

    I wish I could find some more of these to play with. The original that I used was a NE-xx where xx is now forgotten. Google has been of no help so far, except to eventually turn up the British CV2486 datasheet, no doubt obsolete and unobtainable now.
  3. hevans1944

    This some kind lightbulb or...

    It is a cold-cathode neon trigger (thyratron) lamp. I used one of these in the mid 1960s to build a full break-in keyer for my home-brew 80m Novice radio transmitter. The device was used to short my Heathkit SB-301 receiver antenna input each time the transmitter was keyed on, thus protecting...
  4. hevans1944

    Hook Up Wire for PSU

    Broad over-encompassing questions are not useful on this forum. Do your own research and experiments and then ask specific questions to clear up any misunderstanding. For example, don't ask "What is the best transistor for a beginner to use?" Instead ask, "Will a 2N2222 be adequate to provide...
  5. hevans1944

    Where Can I Buy a 100w Resistor?

    And they appear to be physically in perfectly good condition.
  6. hevans1944

    Hook Up Wire for PSU

    My preference depends on application. I usually use Teflon insulated, silver-plated, 24 AWG stranded hook-up wire because I happen to have a large spool on hand. You must use a proper stripper for Teflon insulation though. I absolutely hate thermoplastic insulated hook-up wire because the...
  7. hevans1944

    Where Can I Buy a 100w Resistor?

    So, would that be red-black-red-silver bands for one resistor and brown-black-red-gold bands for the other resistor? Most 100 watt resistors I have seen don't have color codes. They just stamp the value on the body because there is plenty of room to do that. And to dissipate 100 watts in the 2...
  8. hevans1944

    I need to hire someone for a logic design

    @chopnhack: To reiterate, bubble formation in the salt water aquarium is a consequence of water aeration when the organic content (mainly fish poop) of the water is too high. It is removed by a device called a protein skimmer. The OP observed that when the number and size of the bubbles gets too...
  9. hevans1944

    I need to hire someone for a logic design

    So, if a reliable battery operated bubble detector and pump controller with programmable on-time and programmable re-trigger time delay were commercially available, what would you be willing to pay for it? Someone here might take a stab at making a prototype if they had a source of bubbles that...
  10. hevans1944

    Converting Switch/Case statement in C to ASM?

    Yes, but it is a good idea to always declare the variables in the DATA space but you have to initialize or assign values to DATA variables in your code. It is possible for some PICs (but not the PIC10 series) to have variables initialized with the assembler idata directive when code is assembled...
  11. hevans1944

    How Do I regulate 3v DC?

    If you put a fresh set to two AAA cells in your mysterious thingy and leave it turned on, does it work? How long do the two AAA cells last before it no longer works? You have probably blown an internal fuse in your multimeter. Get a new fuse or a new multimeter and learn that you never try to...
  12. hevans1944

    Converting Switch/Case statement in C to ASM?

    The problem, as pointed out by dan1138 in his post #9 on the Microchip forum, was your instruction that attempted to move a literal that you had placed in the accumulator with the movlw instruction into a symbol allocated to code space: movlw .1 ;.175 movwf Delay100ms call...
  13. hevans1944

    Kepco BHK 1000-.02 DM Resurrection...?

    Have you tried Google search engine? Use search string "Kepco BHK 1000-.02 DM ". Also, if you go here you can download a user's manual. Not much good for troubleshooting (no complete schematics of internals), but it does show how to use make external connections and use the power supply.
  14. hevans1944

    MOSFETs' source-drain resistance

    No. The MOSFET body diode is intrinsic to its construction. Some MOSFETs rate their body diode to counter inductor back emf when the MOSFET turns off, otherwise you would have to provide it separately. In an H-bridge configuration current flows both directions through the inductive load...
  15. hevans1944

    MOSFETs' source-drain resistance

    There is a body diode "built in" to the MOSFET. You are reading the forward-biased conduction of this diode when the drain is negative with respect to the source for N-channel MOSFET. The opposite polarity is true for P-channel MOSFET. The actual source-to-drain resistance is quite large because...
  16. hevans1944

    Neon glow bulb (ne-2) arcs/flashes when powered

    I don't read Chinese, but the kΩ at the end of the top line of the two columns labeled SERIES RESISTOR, indicating appropriate resistance values to wire in series with NE-2 type lamps, probably is a clue. @Minder is right: assume small neon lamps have zero ohms resistance (they actually exhibit...
  17. hevans1944

    Transducer AC mv/V to 0-5 VDC Conversion........... I think?

    The 6-488B Manual was quite informative... and it was like a way-back machine that took me to the 1980s and Z-80 microprocessors... it is really quite amazing what creative engineers and programmers could wring out of that "primitive" machine for a dedicated application... floating-point...
  18. hevans1944

    Reactance Question

    No! It's only a "resistance" in the sense that reactance opposes (limits) the flow of current in AC circuits without undergoing any power dissipation. Real resistors also oppose (limit) the flow of current in AC or DC circuits, but in all instances real resistors dissipate real power in opposing...
  19. hevans1944

    Transducer AC mv/V to 0-5 VDC Conversion........... I think?

    When you first posted this I was thinking, "Hmmm... large relay rack, maybe with a table, whirring and spinning magnetic tape drives, blinking lights all over the rack panels, white-coated geek-priests in attendance... very Star Trekkie and not exactly my vision of a custom performance MC shop...
  20. hevans1944

    Transducer AC mv/V to 0-5 VDC Conversion........... I think?

    Yikes! You need to add a ten foot lever arm and hang some weights to calibrate that puppy. I found a spec sheet that says your signal conditioner does provide ±5 V DC analog outputs. Your mission, should you choose to accept it, Mr. Hurley, is to find where on the edge connectors the analog...
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