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  1. hevans1944

    Working with an RC timer and a transitor to power a high current device

    If you can learn to program a PIC (it has taken me several months to learn how to do that), your should be able to blow the socks off your family with some pretty simple external "stuff" because all the magic will be in your firmware. I would go for some LED "chaser" light displays first. This...
  2. hevans1944

    Relationship of frequency and capacitance.

    I generally like @Ratch 's explanation, however I have a small quibble: I think you must have meant the dielectric between the plates. In an electrolytic capacitor, the electrolyte does allow charge to pass through the electrolyte, and in fact the electrolyte serves as the cathode or negative...
  3. hevans1944

    Home made speaker

    There are many programs available as free downloads for both drawing schematics and simulating circuits. I like the one (LTSpice) that Linear Technology offers at their web site, but there are many others. Google is your friend to find all of them. Search for "free schematic capture programs"...
  4. hevans1944

    resistor blown frequently

    You should try to remove the burned area of the circuit board with sandpaper or a rotary tool, deep enough to expose clean circuit board material. The burned area is likely to be somewhat conductive, but hopefully it doesn't go all the way through the circuit board. When done, spray a thin coat...
  5. hevans1944

    resistor blown frequently

    Stick around here long enough and your skill in electronics language will surely improve!:D
  6. hevans1944

    resistor blown frequently

    Two 22 Ω resistors in series is 44 Ω, close enough to the 47 Ω that is burning up, but twice the wattage capability of a single resistor. Two 47 Ω resistors in series, paralleled with another two 47 Ω resistors in series, will be 47 Ω but with four times the wattage capability of a single 47 Ω...
  7. hevans1944

    Working with an RC timer and a transitor to power a high current device

    If you discard R1 and C1 and connect the now free end of R2 directly to a PIC output port, with the emitter of the transistor connected to common (Vss) and your LED or piezo buzzer or whatever connected between +5 VDC (Vdd) and the transistor collector, you should be able to turn things on or...
  8. hevans1944

    Transformer trouble

    Oh, it is so nice to see that the simulation software says your Colpitts oscillator will work. And from the simulation waveform plot (about 3 μs period on the waveform) it appears to oscillate close to 333 kHz. That's quite high for most transformers to pass a significant amount of power with...
  9. hevans1944

    Reading Negative Values of accelerometer

    Apparantly, the function getAcceleration_X() can return a negative value. If this is so, it is converted to a positive value by multiplying by -1 before sending the resulting decimal value to the UART. Note that accelerationX is cast to unsigned short before sending as a decimal number to the...
  10. hevans1944

    [HELP] Astable Circuit as Relay Driver

    Schematics instead of pretty pictures would help. It does appear that you do not have the relay coil connected.
  11. hevans1944

    Home made speaker

    Whew! Finally some sanity in this thread. Thanks, Bob. But what's with the woofers and tweeters (or is it tweakers?)... I thought this thread was originally about how to build your own speakers using common household materials... assuming neodymium rare-earth magnets are common now.
  12. hevans1944

    DC Voltage Measurement to RS232

    Besides wanting to measure -30 V DC to +30 V DC with a resolution of one millivolt, how fast do you want to make these measurements? A few thousand samples per second is probably feasible with a fast RS-232 baud rate, but limiting it to a few hundred samples per second (or less) will prevent a...
  13. hevans1944

    DC Voltage Measurement to RS232

    @Steve_O One millivolt resolution in a 60 volt span means you need at least a 16-bit analog-to-digital converter. Adding ancient RS-232 communications protocol increases the cost somewhat compared to a USB solution. Try this web page for a 16-bit A/D with RS-232 communications protocol. If you...
  14. hevans1944

    Understanding Inductors

    It is a very interesting and informative website indeed. For anyone interested, Google is your friend if you search for "Colin Mitchell electronics". For lots more on the wonders of inductance, resonance, and other amazing aspects of all things electrical, research (Google) Nikola Tesla whose...
  15. hevans1944

    Can a clock pendulum be slowed down by adding a resistor to the PSB?

    I think it should be obvious by now that there is no simple solution to the problem of increasing the period of a pendulum, other than to increase the distance between the bob and the pivot. Modifications to the electromagnetic device that keeps the bob moving in the presence of frictional...
  16. hevans1944

    Can a clock pendulum be slowed down by adding a resistor to the PSB?

    Well, it shouldn't, but I was thinking of a forced pendulum oscillation which requires a lower Q to be effective. The problem is, the simple impulse provided by the electromagnetic "kicker" does not lend itself to the sinusoidal forcing torque described in the document at the linked site...
  17. hevans1944

    Can a clock pendulum be slowed down by adding a resistor to the PSB?

    Maybe you should have sought the advice of an engineer or someone who is very technically minded... before you purchased a thousand of these pendulum movements from Asia. A pendulum is what it is. But that doesn't mean you can't work with the physics. Your pendulum mechanism in its current form...
  18. hevans1944

    Can a clock pendulum be slowed down by adding a resistor to the PSB?

    It looks like the pendulum weight is missing from your photographs. Presumably this weight attaches to the cut-out on the plastic swinging arm. You need to extend this downward to increase the period of the pendulum. There is no electronic solution.
  19. hevans1944

    Wiring/Schematic help with SMC Solid State Auto Switch D-Y7NW

    It sounds like the open-collector NPN transistor is shorted from collector to emitter. This could possibly occur if you connected the +24 V supply to the output (black wire) without a current limiting resistance, and then turned the transistor on. There should be effectively an open circuit...
  20. hevans1944

    Wiring/Schematic help with SMC Solid State Auto Switch D-Y7NW

    The output to the Arduino needs to use a 5 V supply (your lower sketch) for the "pull-up" resistor. The value of the "pull-up" resistor is not critical. It's purpose is to allow the transistor collector to be "pulled up" to the supply voltage when the transistor is OFF, while limiting the...
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