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  1. AnalogKid

    sound activated led flasher circuit

    Gee, that kinda depends on everything you didn't tell us, like what frequencies, what decibel level, what voltage and crrent for the lights, what power is available for the circuit, what you can do, what you can't do, what kinds of components you have or have access to, your skill level is... ak
  2. AnalogKid

    Newbie HELP!! Simple Scematics for Solar Cell-Triggered Switch

    What is the "bigger system"? What are the voltage and current requirements? Also, what power is available to run the switch circuit? And, do you nave a voltmeter and access to some resistors? What you are describing is a simple, small amplifier, maybe only one or two transistors, and there...
  3. AnalogKid

    Old-bie finally inspired for some DIY fun! Need a point in the right direction.

    There are several things to consider as you ramp up. Outdoor/rugged systems need more robust packaging than required for an office environment, and robust usually means closed/insulated. Granted your project will be extremely low power most of the time, but the heat has to go somewhere. Also...
  4. AnalogKid

    Old-bie finally inspired for some DIY fun! Need a point in the right direction.

    Microchip (makers of the PIC microcontrollers) have 8-pin parts that draw a few microamps, plenty low enough for a few months of idle time on a couple of AA or coin cells. There are I/O tricks that can get six buttons into the chip with only one I/O pin. What does "fire the trigger" mean...
  5. AnalogKid

    capacitor plate voltages

    And, both power sources must be connected to a common ground or reference potential. ak
  6. AnalogKid

    4 state illumination controller

    For direct drive applications, I like the AC or ACT series CMOS parts. 20 mA up or down, an output impedance that is more symmetrical than any other logic family, and very robust. Not all logic functions are available in AC, but they are great if you can get them. ak
  7. AnalogKid

    4 state illumination controller

    0-1-2-3 in a rotating pattern = 2-bit counter (both halves of a 4013). With two binary weighted outputs, the two current setting resistors can be equal-valued, summed into the load. Or the counter outputs are buffered with switching transistors and their collector currents are summed into the...
  8. AnalogKid

    Reverse Color Organ

    Please post the Velleman schematic. In the mean time, it sounds like you are asking about an analog inverter. Not the same as a digital not gate because in your case there is no implied reference to invert things about. An inverting opamp with an offset of Vcc/2 or 4.5 V will do what you...
  9. AnalogKid

    i give up.. lm317 + 2n2222

    All text, can't draw a schematic where I am right now. Without an opamp, differential pair, or some other zero-headroom (zero as in way less than Vbe) gain device, a constant current regulator has limitations. When using a transistor's Vbe as both the reference voltage and the setpoint, first...
  10. AnalogKid

    i give up.. lm317 + 2n2222

    Post #36: quote I wanted to correct my post but was away from computers for a while, and you beat me to it. enquote ak
  11. AnalogKid

    i give up.. lm317 + 2n2222

    No. I did look at it again, ran a calc on the 317, saw that you had it throttled back to only 2.5 mA output, and figured out that you were relying on the current gains of both transistors to set the output current. Way back when this was called "dangle biasing". I wanted to correct my post...
  12. AnalogKid

    Is this circuit compatible for charging my gel cell?

    The LM317 can operate with up to 43 volts between its input and output pins, so the circuit does not need any changes because you have a 24 V source rather than an 18 V source. To be clear, you would need a heatsink for the 317 even with a 15 - 18 V source, just not as large. The circuit uses...
  13. AnalogKid

    i give up.. lm317 + 2n2222

    Chris, are you proposing the circuit in post #26 as a solution to the question in post #1? ak
  14. AnalogKid

    Is this circuit compatible for charging my gel cell?

    The Maxim chip is smarter than the circuit in post #1, and Linear Tech makes a similar part that I have used with no problems. The nice thing about the smart chips is that they go into float or trickle mode automatically, so you don't have to set an alarm clock. But for simple and effective...
  15. AnalogKid

    i give up.. lm317 + 2n2222

    Am I missing something, or is this a saturated switch, and Iload is not related to the 317 output current. What I see is the 317 providing 2.5 mA of base current to the first of two saturated switches in series. Did the op requirements change? ak
  16. AnalogKid

    Unregulated power supplies

    A proper gel cell charger has three output states. One is a low current to wake up the battery from long shelf storage or deep discharge. Next is the higher current main charge state. Once the battery terminal voltage hits a trip point, the charger drops down to a low current trickle charge...
  17. AnalogKid

    Is this circuit compatible for charging my gel cell?

    Actually, if C = 7.2 A h, then 650 mA = C / 11, a good starting point for a battery with no manufacturer, part number, or age. A higher charging rate certainly is possible by changing the current shunt resistor as indicated in the schematic. The discussion about a 1.2 A h cell refers to...
  18. AnalogKid

    i give up.. lm317 + 2n2222

    The LM317 is an outstanding component, and was a minor miracle back in its day. But at its heart, it is a *voltage* regulator, and can make bending it to do what you want (other than voltage regulation) harder than a circuit grown to do the non-voltage-regulating task. If what you want is...
  19. AnalogKid

    Is this circuit compatible for charging my gel cell?

    Yah. I've never seen C/0.9 as a recommended charging rate for *anything*. ak
  20. AnalogKid

    i give up.. lm317 + 2n2222

    The classic problem with the classic 317 CC circuit is that all of the output current goes through the resistor. A nuisance for a fixed output, but for variability that resistor becomes a low resistance, high power pot, not a cheap part and not a good approach for long term reliability. OTOH...
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