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  1. AnalogKid

    555 in astable mode

    Your scope shot still does not open, and without that it is dificult to speculate on the spike. What is your acceptable frequency error tolerance? A 555 with quality external components can meet +/-5% or better, but for 2% or less you need a crystal or resonator. ak
  2. AnalogKid

    Need help with long distance circuit

    To Tha and davenn, consider this. The direction the signal current is flowing does not affect the direction of the noise current. Induced noise is the same direction in both conductors; that's why it is called common mode noise. No cancelling occurs in the wires. The cancellation happens at...
  3. AnalogKid

    Need help with long distance circuit

    As noted for any given external cable length, the internal wires of a twisted pair are longer because twisting the wire around something takes more wire. This extra length increases both the series inductance and resistance, and the parallel capacitance. The more tightly the pair is twisted...
  4. AnalogKid

    Need help with long distance circuit

    Within a signal pair, wire-to-wire capacitance actually is greater with twisted pairs than with straight parallel pairs. Also, I assume that in your first sentence you meant to say resistive rather than reactive. Like inductance, capacitance is a reactance. ak
  5. AnalogKid

    LED Strips Display driven from 555 / 4017 counter

    Not all TIP's are created equal. By datasheet, a 4017 will not saturate a TIP31 at Ic=500 mA. Real world parts, almost certainly. But there's not much margin for the base resistor value between undercurrenting the base and overcurrenting the 4017. ak
  6. AnalogKid

    Need help with long distance circuit

    I think a few thousand miles of cable have enough inductance without adding any extra. The first transatlantic telegraph cable was operational in 1858, but Oliver Heavyside's transmission line equations came along 20 years later. To me this says that the first cable was designed and...
  7. AnalogKid

    Voltage regulator for power supply

    The Shutdown pin has an internal current source pullup, but I'd still tie it to Vin with 10K. ak
  8. AnalogKid

    LED Strips Display driven from 555 / 4017 counter

    The 555 and 4017 can run directly off the 12 V rail. Both chips can tolerate up to 18 V. ak
  9. AnalogKid

    12V DC Power source for prototyping

    Many switching power supplies, and ATX supplies in particular, need a minimum load on one output (usually the 5V) to stabilize the magnetics for the other outputs. 10% of the full rated output for that voltage is typical. So if the supply is rated for 5V at 50 A, you need a 5 A load before the...
  10. AnalogKid

    Voltage regulator for power supply

    Please explain how the resonator circuit is supposed to work. ak
  11. AnalogKid

    Touch sensor to activate light for set amount of time

    Is the golf ball rolling down a tube or tunnel or chute of some kind? In other words, is it confined to a narrow space as it passes the sensor? ak
  12. AnalogKid

    IR Switch Trigger in Specific Setup

    ebay has plenty of low-cost PIR and ultrasonic people detectors that will work reliably in the 15" range you cite. What power source is available for the control electronics, and what are the voltage and total wattage of the lights? ak
  13. AnalogKid

    Programmable timer / usb pump

    Your overall plan is sound, but the real world might not play along. The problem with a 5V programmable timer is that most of them have digital displays, and consume power continuously even when the output is energized only 10% of the time. They do not use the custom chips in digital watches...
  14. AnalogKid

    help designing simple 4022 circuit

    Post #1.
  15. AnalogKid

    help designing simple 4022 circuit

    What about his other 8 equations? Also, all of he above schematics have at least one diode structure between the CMOS output and the CV output. This means that the maximum output voltage will be less than 4.4 V, and in one case less than 2.6 V. ak
  16. AnalogKid

    major stress of railway track

    A guy I used to work with now does this. There is nothing magical or exceptionally difficult about it except for the scale. ak
  17. AnalogKid

    LM317 question.

    Dude, I was prodding him to do the math himself...
  18. AnalogKid

    major stress of railway track

    Are you talking about a commercial railroad track? If so, you are talking about hundreds of tons of force, plus modifying the track. Is this legal where you are? Are you qualified to do this work? ak
  19. AnalogKid

    Don't Fence Me Out

    Mist fence chargers are based on a small switching power supply circuit called a flyback. This is the same topology as is used in cars to generate the spark plug voltage. A car battery charger will run one with a little help. The transformer you describe would be correct if you were running...
  20. AnalogKid

    LM317 question.

    1/4 watt should be fine. You know the resistance value and the voltage across each resistor, so you can calculate the actual power dissipations. The components should be rated for at least twice those values. ak
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