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  1. hevans1944

    Voltage Amplifier

    Holy moly, Batman! That one is a BARGAIN at $325 for THREE channels. And an ex-NASA pull too! If I were the OP, I would jump on that if it is still available. There is no way you can build even one channel (successfully, from scratch) for such a low cost. Pricey indeed! Pricey cheeeap! Hop
  2. hevans1944

    Need help testing this circuit

    I didn't realize you and Mark were having a private conversation. He started one with me, too, but it hasn't gone anywhere. If this is, indeed, a high-speed photo-flash application, then the SCR provides the inherent positive feedback necessary for fast triggering of the flash tube. Later, on...
  3. hevans1944

    Voltage Amplifier

    Veeery serious... and expensive at $146 each. They are now available in Europe for € 130,69. The OP should order several spares because it is soooo easy to "let the smoke out" of these hybrid devices until you learn the proper circuit construction techniques and placement of the current-sensing...
  4. hevans1944

    Voltage Amplifier

    Really? All I mentioned were MOSFETs and BJTs. It appears (to me at least) that you are totally unqualified to design and build a high-voltage DC amplifier that will accept a low-level 0 to 3.3 V DC signal and produce a high-level 0 to 300 V DC (or more) drive signal for your off-the-shelf...
  5. hevans1944

    Need help testing this circuit

    What do you mean by "voltage at the testing light led?" Voltage is always measured between two points. If one of the two points is the anode of the led and the other point is the cathode of the led, then it is normal for there to be a voltage measured between those two points if the LED is...
  6. hevans1944

    Voltage Amplifier

    You need a high-voltage op-amp. Try Apex Microtechnology PA-96 for starters. If this is a DIY project, you can also "roll your own" from discrete high-voltage MOSFETs and/or BJTs, but be prepared to "let the smoke out" of a few components before getting the knack of it. The circuit...
  7. hevans1944

    Need help testing this circuit

    Sounds about right. Once it is triggered "on," an SCR will stay "on" until the current through it drops below its holding current or the circuit is opened. With DC applied, this cannot happen unless you open the circuit. I don't suppose you actually read my post #8, where I suggested you use a...
  8. hevans1944

    Need help testing this circuit

    Believe whatever you want. Try to find what you need somewhere else if our answers are unsatisfactory. We try to help those who help themselves. Yada, yada, yada. BTW, I don't personally do schematics much. Maybe someone here will jump in and do that for you.:rolleyes:
  9. hevans1944

    Need help testing this circuit

    Well, let's not denigrate the efforts of monkeys. Monkeys are quite intelligent, especially at copying things that they observe to work. Monkeys, for some reason, simply lack the capability for much of the creativity enjoyed by us humans. "Monkey see, monkey do" is the way we all learn how to...
  10. hevans1944

    Need help testing this circuit

    Okay. In your first schematic (reproduced below) the 470 Ω resistor provides current-limiting for the series-connected LED between +9 V and GND. The LED illuminates the Photo-Transistor (PT) which then conducts current from +9 V through the variable 100 kΩ resistor from the PT collector to the...
  11. hevans1944

    Need help testing this circuit

    Signal flow conventionally proceeds from left to right, top to bottom. Here's one that is even worse: Is it obvious to you how to use "SCR OUTPUT" in the above schematic diagram?
  12. hevans1944

    Relation between pwm frequency and motor speed

    For what it's worth, attached is a PDF representation of the Excel spreadsheet.
  13. hevans1944

    Relation between pwm frequency and motor speed

    There is NO relationship, per se. You are confusing a method of power control with methods of motor speed control. PWM, or Pulse-Width Modulation, is a means to control the delivery of an average current to a low-impedance load from a low source-impedance voltage source. If such a voltage...
  14. hevans1944

    Frequency and time confusion

    Interesting thread. I remember that "ah ha!" moment near the middle of the previous century when I realized that looking at things in the "time domain" versus looking at the same things in the "frequency domain" was still (always) looking at the same things... just a different perspective is all.
  15. hevans1944

    Measure temp, humidity, brightness

    Why is there a "requirement" to program this microprocessor (whichever one you choose) in assembly language? Is this for an assembly language course? Or is this a hardware-oriented course? RS-232 is a hardware protocol specifying a means to asynchronously exchange a serial data stream. Many...
  16. hevans1944

    Ultrasonic Water Level Sensor

    The easiest, simplest, way to sense when water level has dropped below a certain level is to use a small plastic float (closed-cell styrofoam works well) inside a vertical plastic tube with one open end of the tube immersed in the water. The other open end extends into air. Now, just detect...
  17. hevans1944

    Cooling electronic circut ?

    Don't see a link to the seller in your post. Sounds to me like you went for a cheap price instead of a reliable product that performs to a published specification. Umm... did the seller not provide any specifications? Did you provide the seller with specifications of what you wanted? Sounds to...
  18. hevans1944

    Cooling electronic circut ?

    How desperate are you? You can immerse the entire board in a non-conductive liquid, such as mineral oil or (expensive) Fluorinert, and then circulate that liquid through a liquid-to-air heat-exchanger with a peristaltic pump moving liquid on the liquid side and a small fan moving air on the air...
  19. hevans1944

    Server Move

    Yes it was! Thanks @Ian for making the upgrade. Not sure I see any difference in speed (it has always been very fast to respond here in the States), but it's nice to see you always have your head "under the hood" to make sure things are ticking along properly.
  20. hevans1944

    DC to AC converter

    Excellent observation! I hear that reliable mains power is a huge problem in India, only somewhat alleviated by the fairly recent availability of relatively "inexpensive" photo-voltaic solar array panels backed with automobile batteries. Here in the USA, I needed some means to power my HP...
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