Search results

Search Forums New Posts
  1. hevans1944

    Anyone have any oscilloscope recommendations?

    Yeah, I was a self-taught youth and just beginning to acquire test equipment in the late fifties. My first real instrument was an RCA VoltOhmyst VTVM kit. It was many years later before I purchased a VOM with mirrored scale and 20,000 ohms per volt sensitivity. The EICO oscilloscope and...
  2. hevans1944

    Floating current source

    Imagine, if you will, that your original circuit with +Ve, -Ve, GND, Vin and it's associated GND, and Iout, taken between the mosfet drain and -Ve, are all enclosed in a "black box" completely insulated from the outside world. +Ve and -Ve are supplied from batteries or from well-isolated...
  3. hevans1944

    How to connect tweeter with speaker, series or parallel?

    You have to use this search string: "ALDA expression of quality" all in quotation marks. Appears to be Russian origin.
  4. hevans1944

    Floating current source

    That's not a need. It's a want because "the PCB has already been designed and populated." Some one should have considered the need for a floating current source before designing and populating the PCB. Sorry about your design oversight, but caca occurs and sometimes you have to start over...
  5. hevans1944

    Tenma 72-4045A

    The slide switch in the upper right corner allows you to connect the A and B power supplies in series or in parallel and to have the B supply output vary (track) with the A supply control, or have both A and B supplies independently controlled. The Tenma 72-4045A appears to be virtually the...
  6. hevans1944

    Happy New Year!

    Live long and prosper in MMXVII.
  7. hevans1944

    Floating current source

    Please answer the question that @Gryd3 asked in post #7. What are you trying to DO with your "floating current source"? I notice that your control input is referenced to "ground" so if you want the current source to not care about that, just power up the op-amps and the mosfet with ±6 V...
  8. hevans1944

    Recommendations for a budget programmable electronic load?

    Why don't you let Google be your first friend? Then provide some specifications about what kind of load you want to attach. Is this an AC or a DC programmable load? What voltage and current and power specifications did you have in mind? Any idea of the duty cycle? Will it require the water...
  9. hevans1944

    Common gate amplifier gain

    Why would you expect Vout to be greater than Vin? Where would "gain" come from?
  10. hevans1944

    Relay Help!! 24v to replace 18v?

    Is the solenoid valve a typical low-voltage AC, with the coil voltage supplied from a nearby step-down (doorbell) transformer? Or is it perhaps supplied from a step-down transformer mounted on the Vaillant circuit board? There may be a mis-match between the solenoid voltage requirements and...
  11. hevans1944

    Relay Help!! 24v to replace 18v?

    Worn contacts you could probably live with, but burnt contacts indicate something is wrong with the circuit (or circuit design) of the load being switched, and an arc is forming when the contacts open to disconnect the load. Sometimes arcing also occurs when contacts close, because of contact...
  12. hevans1944

    Relay Help!! 24v to replace 18v?

    It is unlikely that the relay you purchased with a 24 V coil will operate reliably in place of a relay with an 18 V coil. What makes you think the existing relay is "worn out" instead of something else being the culprit? Relays hardly ever wear out, but the contacts can be damaged, sometimes...
  13. hevans1944

    Mooshimeter

    I purchased one before moving to Florida, for use with my Galaxy 4 Smartphone. Didn't really have enough time before the move to "play" with it a lot, but I liked what I was able to explore in the short time available. I like the fact that it digitizes two channels simultaneously, each with 24...
  14. hevans1944

    Circuit Design

    You have this all wrong. The ideal inductor has zero resistance, so in series with a current-limiting resistor, R, after five time-constants equal to L/R seconds, the current in the inductor will have increased exponentially and asymptotically to approximately I = V/R, where V is the supply...
  15. hevans1944

    Circuit Design

    Back in the day... well, about the middle of the previous century... the standard "introduction" to electronics was to build a crystal radio set with a one-transistor audio amplifier. This involved winding a coil (inductor) on a paper core (perhaps after applying a coat or two of shellac to...
  16. hevans1944

    A Basic description of Resistors in Series or Parallel

    We are here to help each other, whether newbies or "old pros" and everyone in between. It will take you awhile to become comfortable with circuit analysis and the jargon used in electronics. Google is your friend, but don't trust the information from just one site: cross-reference and verify the...
  17. hevans1944

    Physical difference between low/high transformers?

    Typos are the norm for mobile devices. I apparently have fat fingers, so I avoid using my Galaxy 4 "smart phone" for typing in anything much more complicated than a telephone number or an e-mail address. IMs (Instant Messages) for me are a PITA. However, most of the time the intent is clear from...
  18. hevans1944

    Can anyone provide me a link or book how to make a woofer at home?

    You old timers are about to open a doorway into an abyss of information and misinformation regarding loudspeakers and loudspeaker enclosures. Everything that can be said, and needs to be said, has already been said at least fifty years (or more) ago. OTOH, putting together my very own DIY...
  19. hevans1944

    A Basic description of Resistors in Series or Parallel

    Resistors in series add their values. So with three resistors in series the value is R1 + R2 + R3. Resistors in parallel have a value that is the reciprocal of the sum of their reciprocal resistances. So, if all the resistors are equal in value, then three resistors in parallel would each have...
  20. hevans1944

    Need help identifying this

    That appears to be an "open construction" wire-wound resistor AKA a heating element. Can you measure its resistance? Any idea where it is located in the circuit? This might have been used to limit the motor current of the toy car, especially if the wire that it is wound with has a large positive...
Top