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  1. AnalogKid

    Is this circuit compatible for charging my gel cell?

    In post #7 you said: This is MY circuit and it is only designed for very low current to charge a 1.2AH battery. 1300 mA seems a bit high for a 1.2 A h battery. ak
  2. AnalogKid

    i give up.. lm317 + 2n2222

    The LM317 is thinks as a voltage mode device. It has an internal reference voltage, and manipulates the output in whatever way it can such that the output is greater than the adjust pin by exactly that reverence voltage amount. Because a resistor has a directly proportional relationship...
  3. AnalogKid

    4 state illumination controller

    Page 2 of the datasheet lists 9 different models of the BuckPuck. We need to know exactly which one you have. It determines the nature of the control circuit. What you want to do might be doable with the 4017 but easier with a different chip. Also, what are you going to use to power this...
  4. AnalogKid

    4 state illumination controller

    Actually, ak said when the count reaches 4. Talking about the 4017 can be confusing because Reset does not clear all outputs; it puts the counter in its first state, which is called 0. So the 5th state, which is what you use to drive the Reset if you want 4 active states, is called 4. ak
  5. AnalogKid

    4 state illumination controller

    Don't think so. 4017 outputs go high, and the reset input is enabled high, so the instant "3" went high it would go low because of the reset. For a 4 count rotating circuit, tie the "4" output to the reset. There will be a very short pulse on the 4 output, but 0-3 all will be normal. ak
  6. AnalogKid

    contact sensor based on soft dance pad sensor

    The sensor in post #1 is not capacitive. It is a contact switch. The upper and lower pieces of plastic have conductive ink patterns screened on them in orthogonal directions. The center white foam piece is an insulator with holes in it. When pressure is applied, the center foam is compressed...
  7. AnalogKid

    Phase shift

    For 50 Hz, almost any opamp will work. ak
  8. AnalogKid

    Which transistor to choose for my regulators !!!

    My experience indicates that that is more of a concept than a rule. ak
  9. AnalogKid

    Is this circuit compatible for charging my gel cell?

    P = E x I Measure the battery voltage, and subtract that from 24. Let's assume 10 V for now. 24 - 10 = 14 V. That is the initial voltage across the LM317 regulator. Select a resistor from those on the drawing to set the charging current. For a 7 A h battery, keep it below 700 mA (capacity /...
  10. AnalogKid

    Which transistor to choose for my regulators !!!

    P = E x I Power equals voltage times current. Example: If your 5V circuits draw 1 amp total, and this is coming from a 7805 and a 24 V source, then the power in the regulator device is (24-5)V x 1 A = 19 watts. Without a substantial heatsink, the 7805 will overheat in a few seconds. So for...
  11. AnalogKid

    What Potentiometer should I get to control the speed of a computer fan?

    You're fine. It's just that anyone with any experience at this jumps past the series resistor method so quickly it is a blur, especially if they want variable control. As I said, it is very inefficient. But it works just fine if you pay attention to the power levels. The pot you linked to...
  12. AnalogKid

    What Potentiometer should I get to control the speed of a computer fan?

    A BLDC (Brush-Less DC) fan is a wierd combination of a constant resistance and constant current device. As the voltage to the fan is decreased, the current does decrease, suggesting constant resistance, but not linearly as it would with a resistor. Still a constant resistance is a reasonable...
  13. AnalogKid

    Spice Circuit

    Even though it is a very poorly drawn schematic, all of the information is there except the definition of the "trigger". In terms of the circuit as drawn, it can be any kind of pulse up to +20 V peak amplitude. As long as it is above 2 or 3 volts, the drain will be "shorted" to GND. Any...
  14. AnalogKid

    Giant newbie, needs help regarding transmitter

    Your description of basic information made no sense to me. Do you want to transmit the number 24? Why? Also,transmitting to wnat? An FM radio, an ISM band data receiver? Befpre we get to answers, lwts work on the question a bit. Noticed that I didn't even mention "heroic spin"... ak
  15. AnalogKid

    What Potentiometer should I get to control the speed of a computer fan?

    This type of control is the most basic, and the most inefficient. Important question - do you want to just slow down the fan a bit, or dial it all the way down to 0 speed? ak
  16. AnalogKid

    AC plug for DC purpose?

    Those look like knock-offs of Andereson Power connectors, the gold standard of golf cart chargers. The contacts are supposed to be crimped onto the wire, not soldered. Pull=out probably is caused by not enough heat and/or flux during soldering. If might be counter-intuitive, but crimping is...
  17. AnalogKid

    Reviving an LED Lantern

    Just a moment...just a moment... Let's look at the pc board again. Given the presence of the diodes and the single 330 resistor, here's my guess: The power jack in the middle of the board is for an AC wall wart, just a transformer with wires. The diodes rectify the AC for charging and...
  18. AnalogKid

    Energy Monitoring (Formulas and methods help)

    The isolated interface circuits to high voltage AC and high current AC; you know, the a.n.a.l.o.g stuff. ak
  19. AnalogKid

    Reviving an LED Lantern

    That is an industry standard battery available from Batteries Plus, DigiKey, Mouser, etc. 6V, 4 A h. Without have a datasheet, I'd say the normal max. charging current is C/10, or 400 mA. I would limit the charging current to 50-100 mA to be safe until you know how it is responding. If you...
  20. AnalogKid

    AC plug for DC purpose?

    Generally speaking, connector contact spacing, the air gap between metal parts, sets the max. operating voltage; metal thickness sets the max. current rating. So a connector that is rated for 15 A at 1000 V is good for only 15 A at 1 V. The limiting factor is heat generated by the resistance...
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