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  1. AnalogKid

    Beginner needing help - Simple timer circuit for reversing 5v motor

    Here is a completely stand-alone reverser circuit with minimal parts count. The max period is just under 9 minutes; add capacitors in parallel with C1 to increase. Note: C2 and C3 are decoupling caps for the 555's. They are shown near the Reset pins only because that is a convenient place to...
  2. AnalogKid

    Beginner needing help - Simple timer circuit for reversing 5v motor

    I don't understand this. If you already are running 5 V power and GND from somewhere to each motor, then why is one more wire "impossible". Or, what about a circuit (actually, 70 circuits) near the Arduino that sends reversing power out to the motors on 70 2-wire links? Arduino -> 70-stage...
  3. AnalogKid

    Help me design a water heater circuit that automatically turns-off when the heater reaches a boiling

    Help you, or give you? Show us what you've got so far. ak
  4. AnalogKid

    Hopefully this has a simple answer. Concerning grounding Boost converters.

    Maybe, depending on many details about the source to each converter, part numbers for both converter chips, the nature of the loads, and a connection drawing. ak
  5. AnalogKid

    Now I am going to ask 3 stupid questions, please dont laugh. but i cant seem to find info

    I remember the circuit, but I don't see any postings of mine in the thread. Did you post the same project on another forum? ak
  6. AnalogKid

    Now I am going to ask 3 stupid questions, please dont laugh. but i cant seem to find info

    Because a Variac basically is a tapped inductor, its current rating is limited by the wire gauge. Winging some numbers here - let's say it is wound with #22 wire and rated for 120 V, 1 A. When you turn the tap down to the 10% point (12 V), you cannot pull 10 A out of there because that 10 A has...
  7. AnalogKid

    How do I replace this pot with 2 knob pots, coarse fine.

    The problem is that that pot is not a signal adjustment, but a gain adjustment. Adjusting it varies both the series and shunt legs of the negative feedback loop. The gain range of the original circuit is from 9 to 1801. Without getting into the issues attendant to asking an LM358 to deliver...
  8. AnalogKid

    Slotted optical switch

    Nope. 73's schematic is what I was suggesting. With the optocoupler datasheet you can calculate the max current available to the LCD before the zener is starved and the output voltage sags below 3.3 V. ak
  9. AnalogKid

    Alternating relays momentary closure

    Great news, glad it worked out. Can you post your final schematic? ak
  10. AnalogKid

    Slotted optical switch

    No matter what the values of R1 and R2 are, a 10K / 100 ohm divider means 1% of the system voltage will be available to the LCD (after the other errors are corrected). I can't draw schematics this week, so here is a text suggestion: Diode side: 9 V 470 ohms anode cathode GND Transistor side...
  11. AnalogKid

    What is the difference or similarity between these 2 pot circuits?

    Not knowing the rest of the regulator circuit, I'd start with the top schematic. The lower one is a variable resistance in series with a setpoint, and may have very little effect if the input impedance of the rest of the circuit is high. The upper one works as a coarse/fine resistance no mater...
  12. AnalogKid

    Beginner needing help - Simple timer circuit for reversing 5v motor

    I might have missed this back in the thread - what is the running current for one motor at 5 V? Also, does the running time for each motor have to be settable in precise increments, or is an adjustment pot acceptable? If the running current is less thean 100 mA and a pot is acceptable, then...
  13. AnalogKid

    Metal Door Loop

    There is no power in a door. A door is not a source of electron flow. ak
  14. AnalogKid

    Activating a pump based on water flow

    Whoever proposed that was a smart guy.
  15. AnalogKid

    Activating a pump based on water flow

    Reduce R2 to 10K Increase R1 to 10K Add a 100K resistor from the base of Q1 to GND. ak
  16. AnalogKid

    Activating a pump based on water flow

    Not always true. The sensor is a magnet and a hall effect device. I can stop in either state. ak
  17. AnalogKid

    Activating a pump based on water flow

    Circuit in post #2. Rt = 470K Ct = 2.2 uF 2N2907 can be 2N3906 or 2N4403 A possible problem is that the sensor output can stop in either state when there is no flow. In that case we might have to AC-couple the sensor signal. ak
  18. AnalogKid

    Call or Signal Box for Warehouse

    What are the power sources for the alarms, lights, and control circuit? ak
  19. AnalogKid

    Activating a pump based on water flow

    That confirms a 12 V coil. I was hoping for a coil wattage number. Based on the sensor data and your application, can you estimate the frequency of the pulses out of the sensor? ak
  20. AnalogKid

    Activating a pump based on water flow

    No way. Make sure you are metering the correct pins. Also, what is *all* of the writing on top of the relay? ak
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