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  1. hevans1944

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

    There is a Himmelstein Signal Conditioner Model 721 that will provide ±5 and ±10 VDC outputs. It doesn't appear to require a rack-mounted console either. You should look into it. It would help if you provide us the model/part numbers on the "Signal Conditioner (exciter)" you are currently...
  2. hevans1944

    Need help identifying capacitors

    Twenty years is really pushing it for elecrolytic capacitors. The electrolyte paste slowly dries out over the years. Many techs replace all the electrolytic capacitors on equipment this old because the cost of troubleshooting exceeds the cost of the components. And if some haven't failed yet it...
  3. hevans1944

    Frequency divider (less than 1MHz)

    You need to divide the output frequencies by four before phase-locking. The goal is to drive the AFM cantilever with two frequencies that are one fourth the 150 kHz and 160 kHz frequencies, hopefully preserving the relative phase with respect to the original frequencies (which the PLL should do).
  4. hevans1944

    Frequency divider (less than 1MHz)

    If you can resolve two (and only two) distinct peaks with the spectrum analyzer, I assume you are connecting the spectrum analyzer input to the summed waveforms, f1 and f2, which are used as references for the two lock-ins. It should be possible to separate these, with band-pass filters, for...
  5. hevans1944

    Having issues with EEG circuit

    Rather than starting a new thread, you should post as an addendum to your original thread since the original thread is still open. @Arouse1973: We've already been down this stupid Instructables road.
  6. hevans1944

    Frequency divider (less than 1MHz)

    @ehsan66 Thank you for the detailed reply. The block diagram is appreciated, but I will have to print it out to examine it closely. Is there an on-line resource for this image? Also, are you also using an Asylum AFM or some other manufacturer? Please provide manufacturer and model number of the...
  7. hevans1944

    review my design and let me know if anything will go wrong

    There is a lot wrong with it. I would not plug it in. You should be most concerned about the 8 Ω loudspeaker being connected across the 220 V AC power line L and N terminals if RLY1 somehow became energized. That whould make for a rather nice explosion, perhaps melting the NO contacts on RLY1...
  8. hevans1944

    Frequency divider (less than 1MHz)

    Your subsequent comments didn't "clarify" anything for me. What does it mean that "two different frequencies" are phase aligned? What is the digital nature of the summed signals? Is this a digital summation of two digital signals using a 16-bit adder? Do the digital signals represent sine...
  9. hevans1944

    Mosfet / Gate drive problems

    "A few pints short of gallon" I just made up to substitute for "a few cans short of a six-pack" since I don't know if "six-packs" are available everywhere or it that's just an American expression. I got a similar "shocking" experience with an industrial low-frequency (about 450 kHz) induction...
  10. hevans1944

    Future

    @future: If you don't mind, please add to your profile information: where you are located, your age or year of birth, your current occupation, and any electronics experience you have. This information will help us tailor our responses to your requirements and abilities.
  11. hevans1944

    Need to replace DC gearmotor with a stepper one

    Infrared-transparent black caps over the photo sensors might help with the stray light problem. Most plastics are transparent to infrared radiation. Or just use a black plastic strip in front of all the sensors and mount the circuitry in a light-proof box, maybe covered with aluminum foil on the...
  12. hevans1944

    Simple Conversion from Battery to Plug-In

    Or you could connect several (try three or four) 1N400x diodes in series to drop a 5V wall-wart down to the 3V that two D-size cells in series provide. Anything from the 1N4000 series will work: 1N4001, 1N4002, ... up to 1N4007, whatever you happen to find at Radio Shack. The 'Shack sells power...
  13. hevans1944

    Need to draw 5 amps

    If you do go with the PSU you selected, you need to mount it in a box, wire a fuse and a power switch in series with the mains, perhaps add a neon power on indicator, and provide a strain-relief grommet where the power cord enters the box. You can purchase illuminated rocker switches with a neon...
  14. hevans1944

    Frequency divider (less than 1MHz)

    Getting the input sine wave frequency divided by four is the easy part. You need a Schmitt trigger to convert the sine wave to square pulses which you then supply as clock signals to a divide-by-four binary counter. The counter output will be square waves at one fourth the frequency of the sine...
  15. hevans1944

    Mosfet / Gate drive problems

    I had my first introduction to ham radio visiting a mentor in my youth while living in Morristown TN with my grandparents in the mid 1950s. He was a single man in his twenties and he owned a Radio and TV repair shop. He managed to tolerate my questions about electronics, probably because he had...
  16. hevans1944

    Mosfet / Gate drive problems

    I received my Novice Amateur Radio License (KN8UTJ) while serving in the Air Force from 1963 to 1967. IIRC the "ticket" was issued in the summer of 1966 and expired in the summer of 1967, soon after my enlistment was finished. I should have traveled to Columbus OH and taken the tests for either...
  17. hevans1944

    Mosfet / Gate drive problems

    @TedA go back and read post #17 and those following. The problem has been solved.
  18. hevans1944

    Adding filtered signals from the same source

    @BetaTripp it's good to see you are trying to learn. You are on the right track using the filters in parallel, but without the op-amp to perform the summing function, the outputs will interact when you adjust the resistor values. Correct me if I am wrong, but I guess you are going at this from a...
  19. hevans1944

    Converting Switch/Case statement in C to ASM?

    The AND operator filters out (sets to zero) all bits that don't match the literal. So RANDOM AND 0x02 will return a result of either 0x00 or 0x02 depending on whether RANDOM has bit 1 cleared or bit 1 set. Assuming RANDOM is an 8-bit variable, any value from 0x00 to 0xFF (inclusively) will be...
  20. hevans1944

    how to send signal wirelessly

    Wheels, no, but mouse traps... ain't electronics grand? I found a Victor electronic trap in my back yard a few days ago with a desiccated dead mouse inside. It had four Sony AA cells inside, mostly all dead too. So I dumped the mouse and took the trap inside my house to see what else was inside...
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