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  1. AnalogKid

    Need help with buzzer in LED automotive turn signal circuit

    If 73's idea does not work for you, then there are more options. Please give us more information about the electronic flasher device/circuit/dingus. Is it powered from the turn signal switch, or powered constantly and controlled by an input signal from the turn signal switch? ak
  2. AnalogKid

    Low voltage cut in/cut out

    It is not clear what the signal source impedance is. It sounds like a constant voltage with a varying resistance in series. More clarity is needed, but based on that assumption: 1 - LM324 4 - 1N914 diode (routing) 4 - power MOSFET 4 - 1N4004 diode (protection) 1 - voltage regulator (optional)...
  3. AnalogKid

    Constant voltage increment circuit

    Sounds like a potentiostat. What starts the ramp? Press a button? A computer signal? After one ramp. does the output sit at +0.250 V, return to 0 V, or what? ak
  4. AnalogKid

    Low voltage cut in/cut out

    I agree. That's why my example increments total fan power in evenly spaced 1/2 fan steps. Notice that for the "1 full fan" condition I have two fans running at 1/2 power each. ak
  5. AnalogKid

    Low voltage cut in/cut out

    Two fans with 3 states each (off, half, full) equals 9 combinatorial states. Use an LM339 or LM3914 to create 5 ascending states, and diodes to matrix them to any of the 9 possible fan states. For example: Sensor Fan 1 Fan 2 State State State 0 off...
  6. AnalogKid

    Volt diff detection / comparator?

    What is the power source for the circuit? If the INT signal goes to a uC, what is its power supply voltage? Will the difference always be the same polarity? That is, when there is a difference will line 1 always be the one that is greater? How fast do you need the INT signal generation to be...
  7. AnalogKid

    Automated Water Mister (closed circuit soleniod switched off)

    What is the manufacturer/part number/web page for the sensor? What power is available for the monitor circuit? What is the manufacturer/part number/web page for the solenoid? Can you post datasheets for the sensor and solenoid? ak
  8. AnalogKid

    Low voltage cut in/cut out

    The fans have 2-speed controls built in. ak
  9. AnalogKid

    Latching relay for actuator use?

    Does the control circuit run on the same 12 V as the actuator? What is the peak current being switched? ak
  10. AnalogKid

    Low voltage cut in/cut out

    acoustic noise.
  11. AnalogKid

    I'm trying to rig a bike horn to an alarm clock

    That is a critical detail, and renders moot most of the responses so far. 1.5 V is not high enough to turn on a MOSFET directly. One way to go is to turn you schematic "upside down". That is, change the PNP transistor to NPN (2N4401, 3904, 2222, etc.) (emitter tied to GND) and change the...
  12. AnalogKid

    Constant voltage increment circuit

    We need more details about your question. Are you talking about a circuit that takes in input voltage of -250 mV and translates it to an output voltage of +250 mV? Are you talking about a circuit that produces a voltage ramp from -250 mV to +250 mV? Something else? If the circuit has an...
  13. AnalogKid

    I'm trying to rig a bike horn to an alarm clock

    First, add a resistor between the base and emitter of the 3906. This guarantees that the transistor turns off when the input goes open circuit. Something between 10 K and 100K should work. Speaking of the input... This circuit assumes that the signal from the alarm clock goes to a very high...
  14. AnalogKid

    Heathkit IP-18 Circuit Explanation Help

    First - EXCELLENT job of posting a detailed, researched question with documentation. **** for adding reference designators. Generally speaking, there are two basic types of linear voltage regulator topologies. a) the core regulator circuit is a fixed gain amplifier with a variable input...
  15. AnalogKid

    Frequency and time confusion

    The time of a periodic signal is called its period. That is the elapsed time of one complete cycle of the signal. It is the inverse of the frequency. a 10 Hz signal has a period of 0.1 (1/10) second. All repeating signals have a frequency, and hence a period. You use whichever one is...
  16. AnalogKid

    APOLOGIES TO THE GROUP

    Wrong. In a modern passenger car, exactly 0% of the gasoline in the tank goes out the exhaust system. Without qualifying your 30% efficiency number, the vast majority of the other 70% is dissipated as heat, conducted and radiated into the air around the car. Most of that is unused thermal...
  17. AnalogKid

    Spinning/rolls count device

    Something like this? Magnet Reed switch CD4553 3-digit counter Display drivers Displays Reset button OR - get a 3- or 4-digit counter on ebay for next to nothing. Or a kit. ak
  18. AnalogKid

    Op Amp with a/c output

    If the car computer only really needs to see a frequency, but not necessarily a sine wave, then any square wave oscillator circuit will work. Opamp, 555, 1/6 of a CMOS Schmitt trigger hex inverter, 1/4 of a CMOS quad NAND gate, two transistors - lotsa options. What is your experience level...
  19. AnalogKid

    Easiest method to convert analog ac voltage or frequency to digital 0-5v dc?

    For a constant 5 V rectangular wave at whatever the input frequency is, you need some kind of comparator circuit. This could be a simple as one transistor, or as complex (actually, still pretty simple) as a comparator IC circuit. Is the voltage range RMS, peak, peak-to-peak? Does there have to...
  20. AnalogKid

    Combining 2 audio outputs into 1

    Yes, that will work. Note the warning on the product page about significant loudness reduction ak
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