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  1. hevans1944

    APC Back-UPS XS1500

    Sounds like you are making progress! When you plug it into a live outlet (normal operation) it probably wants to "phone home" to its software before it will switch out of the "On Battery" mode. How else would it know that the computer was active, so it could issue a "shut down" command prior to...
  2. hevans1944

    Question on assembly code

    I am not at all certain whether the ORG directive goes in the assembler or the linker. You probably need at least two ORG directives: one to point to 0xFFFF0, where you put the JMP instruction, and a second to point to 0x8001 where you put the rest of your code. Also check the 8088 docs to see...
  3. hevans1944

    Old RS-232 compatibility with new computers?

    Can you post picture of your force sensor and a diagram showing how it connects to the real world? Does it have a DB-9 or DB-25 connector? How is it powered? Is this a load-cell sensor or a piezo-electric transducer? Why do you think it even has an RS-232 output? Is there any documentation for...
  4. hevans1944

    Question on assembly code

    An absolute assembler does not produce relocatable code. The output is a binary image you load into memory. You may be able to live with that for simple programs. A linker takes relocatable object code from an assembler and creates a loadable binary image, resolving all relocatable address...
  5. hevans1944

    mV signal amplifier

    Yikes! Russian 4-pin thermocouple vacuum gauges! These are not archaic so much as old and reliable. You can find modern versions at Kurt J. Lesker. Pin-outs vary all over the place. They were usually excited on two leads with a low-voltage AC, which heated the thermocouple. The TC lost heat via...
  6. hevans1944

    Leading and Lagging AC Power

    The inductors are added to level the frequency response of the twisted-pair copper wires. Line losses are a result of copper wire resistance and cannot be prevented. Line losses are compensated by adding bi-directional line-balanced amplifiers to the loop circuit every few miles. This limits...
  7. hevans1944

    mV signal amplifier

    There are plenty of pre-built alternatives, but first you have to define the problem before looking for a solution. Answer my previous questions about the sensors. What is the source impedance? What is the range of signal amplitudes? Are the sensor outputs bi-polar or uni-polar? How much offset...
  8. hevans1944

    mV signal amplifier

    Looks like you might be caught between a rock and a hard place. I hated it when things were pushed on me to "make work," especially when the pusher knew less about it than I did. But you know the old saying, "The Boss may not always be right, but they are always the Boss." So I tried to make do...
  9. hevans1944

    Leading and Lagging AC Power

    Power factor correction is a serious concern to utilities delivering power to customers. Reactive power (voltage that is not in phase with the current) cannot be billed for revenue purposes because it isn't real power. Nevertheless, reactive current causes resistive losses in the power lines...
  10. hevans1944

    mV signal amplifier

    Well, good luck with using undocumented Chinese parts for that. The information on the site you linked says these have a gain of 3, which I find highly unlikely but possible. Are the two potentiometers for adjusting gain and offset? Your guess is as good as mine. Why not just hook them up and...
  11. hevans1944

    Simple Amplifier

    The horizontal line at the bottom of your schematic is the circuit common or "ground" and (1) connects to the other lead of your pickup and (2) connects to the negative terminal of the battery.
  12. hevans1944

    Question on assembly code

    Okay, it appears you know what your are doing. The 8255 was the "go to" device for I/O interface back in the day and, as a plus, supported vectored interrupts if you need those. When I was involved with Intel 8080 and 8085 microprocessors back in the late 1970s and throughout the 1980s, I had...
  13. hevans1944

    Product PCB Button Pad has a short circuit

    It probably seemed like a good idea at the time to lay out two, more or less concentric, "circles".
  14. hevans1944

    Where is a good location to connect a 3-Volt relay?

    Those LTV8x4 devices look like they have back-to-back LEDs in them. If so, that means they will illuminate the transistor nicely with AC input to the diodes. The current transfer ratio is small... about 20% or so, meaning you may not get sufficient current through the photo-transistor to...
  15. hevans1944

    Rest in Peace, Kris

    It is so sad to hear Kris Heidenstrom (@KrisBlueNZ) is no longer with us. I will certainly miss him. Kris once posted on my profile page, "You're a mine of interesting information, and we are lucky to have you here :-)" Lucky, indeed! I just returned from a four-day hospital stay, after...
  16. hevans1944

    Where is a good location to connect a 3-Volt relay?

    Perhaps. The OP is trying to "make do" with what he already has available, i.e., a wireless doorbell set. Personally, I would just use a pair of insulated wires of appropriate length to fire off a model rocket. Less chance of inadvertent ignition. But then, I am a kind of conservative guy...
  17. hevans1944

    Where is a good location to connect a 3-Volt relay?

    It will be used to remotely ignite an "electronic match" a small-wattage, low valued resistor used to ignite the engine of a model rocket.
  18. hevans1944

    Where is a good location to connect a 3-Volt relay?

    Yes, although I do not understand why the LED in the optical isolator would "light up" when connected to the "speaker" wires. Well, we actually don't know that it will "light up," but you said an LED you tried did "light up" so I am assuming the LED (which you can't see) in the optical...
  19. hevans1944

    Where is a good location to connect a 3-Volt relay?

    Well, there you go! Just substitute an optical isolator for your red LED and use the transistor side of it it to pull in your relay.. Who knows why the "speaker" wires would light up an LED, but if it works for you, go with it.
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