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  1. hevans1944

    Audio transformer for crystal set help

    IMHO it's never a waste of time to remove transformers and try to discover their specifications through electrical testing. You will learn a lot about transformers that way. You might even get adventuresome and remove the insulated copper windings to salvage the cores to make your own custom...
  2. hevans1944

    How to make a trap?

    You need a mechanical arrangement similar to the lock mechanism on a pistol. The door is restrained by a lever that engages a sear. The sear is restrained by the de-energized solenoid. The sear has a glass-smooth sliding surface where it engages the solenoid armature. Retracting the armature...
  3. hevans1944

    IR Sensor

    Hard to imagine a more impressive undergraduate school project. And the young man nailed it, both theoretically as well as practically. I hadn't thought of re-purposing a printer to serve as the carriage under the inverted pendulum. Of course almost anyone can balance a broom handle of an...
  4. hevans1944

    IR Sensor

    So, are you going to mount your inverted pendulum on a motor-driven wheeled cart and then move the cart back and forth to keep the center-of-gravity of the pendulum over the bottom pivot point? This is a classic closed-loop control design problem. Some insight can be found here.
  5. hevans1944

    footstep power generator

    A very serious worldwide problem is the shortage of potable water for drinking and cooking, not to mention enough water (potable or not) for washing and cleaning. We are surrounded by oceans of water, but desalinization plants are expensive and few. An inexpensive, readily available, method to...
  6. hevans1944

    footstep power generator

    A bicycle is probably the most efficient human locomotive device, especially recumbent designs. However, as @Alec_t noted, human-generated electricity is not very efficient or effective. Try hooking up an automobile alternator to a stationary bicycle and see how difficult it is to light a 100...
  7. hevans1944

    Motor to 3phase connection compatability

    You are probably trying to run a three-phase motor from 220 VAC single-phase house wiring. There is no way this will work and no way to make it work. You will need to buy a single-phase to three-phase converter rated for the horsepower of your motor. These come in two varieties: solid state and...
  8. hevans1944

    Drill bits for homemade PCBs?

    I grew up with the Vulcan M61A! 20mm Gatling Gun while serving with the U.S. Air Force, but it is a bit of a load to carry around. Mine were carried by B-52H bombers. The 30mm GAU-8 Avenger packs a bigger wallop, mounted in a A10 close air-support platform, but depleted uranium rounds may be...
  9. hevans1944

    control system counter up to 9

    @Kath it would probably help us to better help you if you could describe your development environment. The PIC16F877A is a very sophisticated microprocessor with many more functions and capabilities than your problem requires. These "extra" features usually have to be disabled to use it in a...
  10. hevans1944

    Current Limiter Circuit

    Hi Adam... no big deal. You are correct, the voltage will drop if you exceed the current limit. Like most questions here, this one is open to interpretation, especially since we haven't heard back from the OP since you last posted. But I'm with you on so-called "fold back" limiting. Whose bright...
  11. hevans1944

    Determining ratings on stepper motor

    @Hellmut1956 Good old German engineering shines again! I haven't had time to pursue this in depth yet, but Trinamic appears to offer excellent cost-effective solutions to stepper motor drivers and positioners, and they have authorized USA distributors. Thanks for the link.
  12. hevans1944

    Need some guidance with relays and timers

    I would try to find a geared synchronous clock motor such as this one and attach a cam to its output shaft. Use the cam to actuate a microswitch that energizes your solenoid valve for a few seconds once per revolution. In the example shown, this would occur once every six minutes. The problem...
  13. hevans1944

    Pic Programming

    Aw, guys! Clearly this gal is in over her head and doesn't have a clue where to start. I am looking forward to her response to @Harald Kapp 's questions. And processing interrupts without learning first how to light an LED? Who would of thunk that up?! See also her cross post...
  14. hevans1944

    Determining ratings on stepper motor

    Most modern stepper motors are driven with pulse-width modulated constant-current drivers to provide high torque without excessive heating. There are integrated circuits available for just this purpose. Measuring the heat increase with steady DC applied to the windings will provide a very...
  15. hevans1944

    Current Limiter Circuit

    @Arouse1973 I believe you may have confused current limiter with current regulator. The OP wants to build bench power supplies with current limiting. So the load can be anything from an open-circuit down to whatever resistance will draw the maximum current specified. The reference that @Miguel...
  16. hevans1944

    Code execution in ISR too slow.

    Looking at the MA3 datasheet, it appears you need to measure pulse widths with one microsecond (or better) resolution. And for best accuracy you need to measure both the "on" time and the "off" time and compute the angular position based on those two measurements. Have you considered using...
  17. hevans1944

    Homemade DC generator(dynamo) with a spinning coil

    I never said it would be easy or practical. The only requirement was it has to be made from "household materials." Can you offer up some other "household materials" that might work better than a re-purposed hand-mixer?
  18. hevans1944

    Wiring pot as voltage divider across polarities

    And make sure the pot resistance is high enough not to present an excessive load on the power supply that would destroy the pot.
  19. hevans1944

    Homemade DC generator(dynamo) with a spinning coil

    I'm thinking a hand-mixer has a gear box, but probably a worm driving two spurs (one for each beater) so it won't work in reverse. You would have to drive the motor shaft after taking the mixer apart and separating the motor from the gears. And crank it really fast if you hope to light an...
  20. hevans1944

    Need Help Improving Brightness in Multiplexed 7 Segments (6 Digits)

    Yes. See @GPG reply in post #16. Only if the digits are multiplexed. If segments are driven from latches and illuminated continuously, any number of digits can be accommodated. Check out the countdown clock that NASA used to display (to the public) the time to lift-off of the space shuttle...
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