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  1. hevans1944

    Help getting started on new project

    What! Don't we all have one of those spiffy Maker-Bots sitting on the kitchen counter top that can extrude or ooze our heart's desire? And howsabout them tiny nanobots to put it all together? Don't we all have a shaker full of them to sprinkle on our creation to finish it in style? Oh, wait, Dr...
  2. hevans1944

    I can't see how this will work

    The LDR is not only a highly non-linear light-dependent resistor, it is also slow to recover to its "dark" resistance after exposure to a bright light that drops its resistance down into the k-ohm range. The "recovery" time for full dark resistance can be several minutes for some devices. This...
  3. hevans1944

    Electric motor switch thing???

    Can you post a picture of the PSU? Are there any manufacturer's markings such as model number, serial number, name of manufacturer? The PSU can probably be repaired if the Hoover just knocked something loose inside to make it intermittent. Unplug it, open it up and see if there is anything loose...
  4. hevans1944

    Help getting started on new project

    I'ld buy that for a dollar!:D ... If it fits on my wrist and re-charges wirelessly. Ummm... what's it actually do?
  5. hevans1944

    please help!

    If each motor/generator has two wires (positive and negative) you should be able to wire four of them in series for four times the output voltage of any single one. No diodes required. Pay attention to polarity so the voltages add, instead of bucking each other: positive on first motor to...
  6. hevans1944

    alert about distance between 2 objects

    The simplest way to do this is with a string (about one meter long) tied to a clothes pin that actuates a NC switch located on one object that has the alarm. Tie the other end of the string to the other object. When the distance between them exceeds the length of the string, the clothes pin is...
  7. hevans1944

    Making waves into DC

    The concepts @Electro132 has are wrong in so many ways... this whole thread is an energy sink, and I am so sorry I am responding to it.
  8. hevans1944

    Magnetic bush problem in project

    If all you want to do is detect when the two magnets are mated together, remove the inductive sensor and replace it with a pin switch. Adjust the switch in and out of the hole until it reliably actuates when the two magnets are in contact with each other.
  9. hevans1944

    flux / soldering paste..

    As @(*steve*) noted, not everything labeled as "solder paste" (especially if it originates in China) actually has solder particles in it. And those that do contain solder particles vary widely in composition. In your first video, an excellent presentation of SMT re-work using a sub-heater under...
  10. hevans1944

    Step down 240v AC to 24v AC

    You should buy a step-down transformer providing 24 VAC @ 2A (or more) to provide power for your solenoids and contactor. You should buy an inexpensive 5 VDC @ 2A switch-mode power supply to provide power for the Raspberry Pi. Forget about deriving DC from the step-down transformer. It's not...
  11. hevans1944

    PIC16F870 frequency counter

    Let's see... you want to measure the frequency of a square-wave signal that varies from a maximum of 255 Hz to a minimum of... zero? And you want to display the results as a number on an LCD display in the range of 0 to 255? One accurate way to do this is to measure the period of one cycle. So...
  12. hevans1944

    Multi stage shift light with PWM.

    I suppose one could consider a PWM signal to be "digital" but not in a way that is useful to a DAC. As you noticed, there is a trade-off between ripple and response time. The only way around that would be to increase the frequency of the PWM signal, which will decrease the ripple with no affect...
  13. hevans1944

    Multi stage shift light with PWM.

    Don't know what you would use a DAC for. Your signals are not in the form of digital data, are they? Yes, that is a pretty nifty site. The values I gave above for the RC filter yield a step response time of about a quarter-second, which may be too slow for a tachometer shift-point indicator...
  14. hevans1944

    Multi stage shift light with PWM.

    You have several choices, depending on the source impedance of the PWM source. If it is low enough, a simple RC filter will work: apply PWM output to a 10 kΩ resistor in series with a 10 μF capacitor to ground. Take DC filtered output across the capacitor. With PWM, the peak-to-peak amplitude...
  15. hevans1944

    Multi stage shift light with PWM.

    If you filter the pulses coming from your variable duty cycle source, the result will be a variable DC voltage proportional to duty cycle. Apply this to the LM3914 analog signal input. Are the variable duty-cycle and variable frequency ECU outputs related to each other?
  16. hevans1944

    CR1632 (3v) vs. Two AA's

    Then that little power supply should work just fine for your purposes... a heck of lot cheaper than replacing those CR1632 cells. Or you could maybe use a rechargable lithium ion battery...
  17. hevans1944

    CR1632 (3v) vs. Two AA's

    Why are you trying to "hack" a "lifeline alert pendant transmitter"? If it is being used for its original purpose, you could be making it unreliable for its intended purpose, perhaps putting the user's life in peril. Please tell us you are re-purposing this device for some project that does not...
  18. hevans1944

    Choosing right diode..?

    What you are trying to implement is called diode/relay logic. The basic idea is to use a forward-biased diode to "steer" current to the desired relay. This is often implemented as a "wired OR" circuit where one relay can be energized from circuit 1 OR circuit 2 OR circuit 3 ... etc. The AND...
  19. hevans1944

    Wattmeter with analog output

    I thought I posted an alternative method of measuring your ICE efficiency, but it isn't here... perhaps I forgot to click on "Post Reply." What I would propose is not measuring the power input to the AC motor turning the ICE shaft but instead measuring the torque and rotational speed of the...
  20. hevans1944

    Would like to convert a DPDT switch...help!

    This sounds like overkill for "automating" a switch that operates intermittently for three seconds! Just tell folks to release the switch after the door opens or closes, maybe upon penalty of whatever if they fail to do so. My ancient Sears garage door opener operates exactly as you describe...
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