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  1. hevans1944

    LM358 Breathe light

    I agree, after further inspection of the circuit, on the need for a non-polar capacitor at C1. The op-amp U1A will try to maintain its inverting input at Vcc/2 (through negative feedback through C1) because resistors R1 and R2 hold the non-inverting input to that value. Assuming the op-amp U1A...
  2. hevans1944

    LM358 Breathe light

    Ignore my previous post about swapping leads. I thought at first glance that U1B was supposed to be an inverting amplifier with a variable gain set by the series combination of R5, R6, and VR1. As @KrisBlueNZ pointed out, it is a Schmitt trigger, which has only two states: output near positive...
  3. hevans1944

    Converting a projector from incandescent to solid state?

    Amazon has this projector lamp for sale at $37.74 with free shipping. Arrives before Christmas if ordered now. The 1000 lumen rating may be the illumination of the projector. There is a lot of light lost in the condenser lens (usually there is an infra-red blocking filter between the condenser...
  4. hevans1944

    Converting a projector from incandescent to solid state?

    My eldest daughter borrowed my 35mm slide collection last year and had someone scan and store the results on a compact disc. Too bad she forgot to send me a copy, but I did get the original slides back... <sigh> I have an HP and and Epson scanner so I can do this myself. Excellent suggestion...
  5. hevans1944

    Reading data sheet

    You should get 2.0 V with 100 A going through it, polarity of output depending on direction of current. Make sure you provide + and - 15 V DC well-filtered and regulated power to it. Note Ipn (nominal primary current) is only 1/3 the maximum full-scale current of 600 A, and the linearity spec is...
  6. hevans1944

    Trying To Cheat The Laws Of Physics . . . Again. Multi Voltage Power Supply

    Your "totem pole" scheme will work, but as pointed out by @(*steve*) it won't be very efficient. How much current do you need from each of your outputs?
  7. hevans1944

    Converting a projector from incandescent to solid state?

    A 35mm slide projector typically has two plano-convex lenses, with the convex surfaces facing each other, to form a condenser lens assembly. The lamp filament is positioned so its magnified image fills the entrance pupil of the projection lens. You may have to fiddle with an LED lamp to get it...
  8. hevans1944

    LM358 Breathe light

    Try swapping the connections to pins 5 and 6 on the LM358. Oops! Not what I thought it was. Never mind.
  9. hevans1944

    Current limiting strategies for L298N?...

    I somehow thought you were using a Sumtor 42H34913A4 stepper motor, but can't find that anywhere on this thread. What stepper motor are you using for the XYZ axis? What stepper motor are you using for the spindle drive?
  10. hevans1944

    Light sensor Interface

    Yeah, we do presentations here at work using an LED projector connected to a laptop. There is a remote control thingy somehow interfaced to the laptop to select slides from a Microsoft PowerPoint file. It is not at all uncommon for new users to get confused about how to operate it. I kinda miss...
  11. hevans1944

    Light sensor Interface

    You could also use a Bluetooth "clicker" suspended from a lanyard or attached to the wrist. Just push one or more buttons to advance or re-visit a slide. Works from anywhere in the room, minimal programming to recognize button pushes. There are also other wireless devices, similar to automotive...
  12. hevans1944

    Beginner Circuit Help

    Several of the horizontal traces short out parts of your circuit. For example the anodes of D5 and D7 are shorted out by the jumper at the cathode of D12. The anodes of D26 and D27 are shorted out by the jumper at the cathode of D20. Just take a sharp knife and cut the offending traces if you...
  13. hevans1944

    Hello from the UP of Michigan!

    Welcome to Electronics Point, @ziptide! I spent three years (1964 - 1967) in the UP of Michigan as an airman stationed with the 449th Bomb Wing (heavy) at Kincheloe AFB near Kinross, just south of Sault Ste. Marie. There is no better way to spend an evening, when you look outside and see snow...
  14. hevans1944

    Light sensor Interface

    This is an ideal project for wearable, wireless, electronics. Just fit a few MEMS accelerometers orthogonally to a wrist cuff. Use an embedded microcontroller in the cuff (see attached PDF file), or at least connected to it if located nearby, to read and interpret the analog accelerometer...
  15. hevans1944

    Effects of feedback

    And then Google positive feedback, which is generally undesirable in an amplifier.
  16. hevans1944

    Current limiting strategies for L298N?...

    Say what? The L297 generates its own PWM pulses with an on-board RC oscillator. You synchronize two or more (in your case three for XYZ and perhaps four if you have a stepper motor for the spindle) L297 using the built-in oscillator from just one of them to sync to the others. Did you even read...
  17. hevans1944

    Current limiting strategies for L298N?...

    @BGB I'm not sure where this tread is going, but I thought I would jump in to stir the pot a little and maybe learn something too. I've not been on Electronics Point very long, but I have found the advice and comments given by @KrisBlueNZ to be accurate and helpful. We are fortunate to have him...
  18. hevans1944

    Why is relay latching? :(

    Door bells depend on an interrupter contact in series with their coil. The spacing on these can usually be adjusted by bending the fixed contact with a pair of long-nose pliers. Your 5 V door bell may have the clanger pressing the moving contact too hard against the fixed contact for the...
  19. hevans1944

    Replacement Power Supply Project

    The writing on the picture shows two 15 VAC windings while the blurb advertising this transformer says 2x 18V. Who knows which is correct? If you can live with the supposedly reduced voltage (from 18 VAC to 15 VAC) this transformer has the power (VA) capacity to replace your original 22 watt...
  20. hevans1944

    Christmas Gift for my 15 year old electronics enthusiast

    My face is red! :oops: Sometimes a Mum has to also be a Dad. This Mum seems to be doing just fine wearing the Dad hat, but then women are soooo much better at multi-taskinng than men are. My apologies, @scrumpet. But my advice to resist the temptation to "tidy up" the messes still stands.:D
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