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  1. hevans1944

    Tried my hand at SMD soldering.

    Yikes! Looks like you need a little more flux and perhaps a hotter iron, or maybe just a hot-air soldering device. The connections should be smooth and shiny, not pitted, lumpy, and irregular. Capillary attraction and surface tension are your friends.
  2. hevans1944

    Programmable Potentiometer/Resistor For 12V DC Motor

    It's way above my pay grade for the moment, but this looks like an ideal candidate for a cell phone app communicating with an Android Uno over a Bluetooth link. The cell phone app would allow you to create a graphical acceleration profile that gets down loaded to the Arduino producing PWM power...
  3. hevans1944

    MC6802 IRQ Pulse

    The only (partial) schematic I have seen appeared in post #7. It shows the 555 connected as a free-running astable oscillator with its output on pin 3 connected to the active-low IRQ input on pin 4 of the 6802. What does a Valid Memory Address have to do with the 555?
  4. hevans1944

    recipe for LED salad

    Never connect LEDs in parallel.
  5. hevans1944

    I need a looping digital timer

    Excellent description of what you want to do. Personally, I don't believe a timer is going to be very useful as an aid to production. You need something that counts the number of units completed every minute, providing the worker with a running display average of the rate of completion. For...
  6. hevans1944

    I need a looping digital timer

    Typical newbie question, asking for a product instead of a solution to whatever the real problem is. @Dexter Wilks please describe what you are trying to do rather than tell us a "looping digital timer" is the best solution. Oh, and welcome to Electronics Point. Lot of good help here if you ask...
  7. hevans1944

    PCB laminates' effects on data

    The problems associated with skew are driving the use of integrated electro-optical wave-guide methods of data transfer for use at very high data rates. The same problems of dielectric uniformity still exist however. Good luck approaching this type of problem at the hobbyist level. Measuring...
  8. hevans1944

    Resistance of different points of a circuit

    I guess the important thing here is knowing how to calculate the values for series and parallel resistor configurations. You need to remember that series resistances add and that parallel resistances, expressed as conductance G = 1/R, also add. Convert all parallel resistor values to conductance...
  9. hevans1944

    Hi from NSW Australia

    Hi, and welcome to Electronics Point!
  10. hevans1944

    Resistance of different points of a circuit

    There is no such thing as resistance at a point. Resistance, like voltage or potential, is always measured between two points. A = 100 kΩ is meaningless. If your point A were on the other side of R1, you could consider the resistance from A to B with R3 and R4 removed from the circuit to be B =...
  11. hevans1944

    MC6802 IRQ Pulse

    That would be a good use for a periodic interrupt too, but we need to see some disassembled code at the ISR vector to get any further. Not necessarily. I am not that familiar with the 6802 microprocessor. This product was introduced late in the last century, and not by Intel whose products I am...
  12. hevans1944

    How do get Arduino to read the angular speed of a rotating shaft?

    There are more than two types of rotary shaft tachometers, some digital and some analog in nature. The simplest digital tachometer sensor is any device that produces one or more pulses per shaft revolution. A typical analog sensor produces a voltage that is proportional to shaft rotation rate...
  13. hevans1944

    MC6802 IRQ Pulse

    IRQ is a maskable interrupt, and the default state after a processor reset is to disable IRQ. So, just because it is being asserted every 80 ms or so does not mean the 6802 firmware is paying any attention to it. Your will have to disassemble the firmware code to determine when and why IRQ is...
  14. hevans1944

    Arduino vs raw PIC, Atmel etc

    I think I read somewhere (probably in the Arduino documentation) that the Arduino IDE was written in Java. One of the IDEs for Processing is also based on Java. There are two other Processing IDEs based on JavaScript and Python. See this link for more information on Processing. Almost on topic...
  15. hevans1944

    Arduino vs raw PIC, Atmel etc

    @Old Steve : Great link! When I purchased my Arduino UNOs earlier this year (along with a whole bunch of shields at Radio Shack) after receiving one as a Christmas present two years ago. I downloaded the datasheet for the Atmel ATmega 328P thinking maybe I could program this powerful μP with...
  16. hevans1944

    Magnet Alarm Circuit Board, Battery Power

    @Old Steve you may not have noticed that I quit responding to this thread when it became obvious that @p1ne didn't have even the slightest clue about what was going on, even after @davenn and some others took the time to explain things. Some people here just like to tinker (nothing wrong with...
  17. hevans1944

    Arduino vs raw PIC, Atmel etc

    @Old Steve Hey, welcome to the forums! It's good to see another "seasoned veteran" responding here. Also, now that the beard is gone, would you please post another profile picture? I used to shave my beard off once each year, just so I could see who was hiding under there. I can't remember the...
  18. hevans1944

    Ground loop filter?

    Toroids are useful cores when minimal magnetic flux leakage and significant amounts of power are design parameters. That said, an E-I stack of laminations is MUCH easier to wind primary and secondary windings. With a toroid core you generally need to wind all the wire on a shuttle first and then...
  19. hevans1944

    Relationship of frequency and capacitance.

    @Ratch : Interesting comment. I didn't want to confuse John yet with the concept of Q until he has a firm grasp of what is going on in a capacitor (and an inductor). In practice, Q is of course very important to circuit behavior and it leads to the kind of bogus "definitions" you mentioned. I...
  20. hevans1944

    resistor blown frequently

    It is possible to cut out the damaged area of the board (assuming it is NOT a multi-layer board... in which case you are SOL) and then epoxy in place a clean section of bare FR4 board material. That will at least give you support for wire-lead components if you drill appropriate holes through...
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