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  1. Alec_t

    Call Progress tone

    This article details the various call progress tones for your part of the world. Something an Arduino should manage easily.
  2. Alec_t

    Output Voltage Selector

    Try using a respective pair of back-to-back PFETS for each supply, like this (only one pair shown):- Edit: One of the FEts shown should be flipped left to right so that they are back-to-back.
  3. Alec_t

    Very Fine Cable?

    ...or you can use a single copper strand from a flexible cable.
  4. Alec_t

    Amplitude

    It could be either.
  5. Alec_t

    Very compact voltage dropdown

    If you have the space, then C cells look to be the most cost-efficient. Depending whose figures you believe, an alkaline C-cell has about 3.6 times the mAh capacity of an AA cell but costs about 1.7 times as much as an AA.
  6. Alec_t

    Very compact voltage dropdown

    You could run both bells in parallel from either one CR123A battery as Bob suggests, or two AA alkaline cells. The CR123A has a rated capacity of 1500mAh whereas AA alkalines have a ~2500mAh rated capacity and (depending where sourced) are cheaper.
  7. Alec_t

    Remote Control - The Right Way To Fix It

    You've shown that there is no IR emission. Try measuring the voltage across the IR LED (preferably using an oscilloscope, but a DMM will probably suffice). If it changes when you press any button on the remote then that suggests a dead LED.
  8. Alec_t

    Charging lead acid battery

    You need a power supply voltage of at least 13.8V to charge a 12V lead acid battery. This is worth a read.
  9. Alec_t

    Very compact voltage dropdown

    Minimum maintenance would be if the bells were powered by a mains-supplied converter. Nowadays they're not much bigger than the mains plug itself. Using a USB (5V) charger, just 3 diodes to drop the voltage would give you roughly 3V, like this:
  10. Alec_t

    12V DC convert for 9V DC

    :confused: So why do you need a 9V supply?
  11. Alec_t

    Very compact voltage dropdown

    Welcome to EP! Actually, penlite (AA?) cells have a greater life than a 9V battery (PP3?). You would need to connect the two alarms in parallel, so the load current for the 9V battery would be 2c, i.e. twice the load current 'c' that one alarm draws. Dropping from 9V to 3V at 2c load current...
  12. Alec_t

    DC-DC Voltage Step Down Module

    In the first pic it looks as though pins 4 and 5 of the IC may be shorted by solder. The two inductors are of similar physical size but quite different values. That may or may not matter.
  13. Alec_t

    DC RC circuit with buzzer

    If you have access to an oscilloscope you could see what the voltage across the capacitor is doing.
  14. Alec_t

    Check if schematic is correct

    It is preferable to post your images on this site, using the 'Upload a file' button. Which IC are you using? The LED should have a series current-limiting resistor.
  15. Alec_t

    Can you please help me with my project?!?!

    Connect the buzzer to the circuit with a long cable (bell wire, loudspeaker wire).
  16. Alec_t

    Woo Woo need a diode ?

    It might be cheaper to buy the waves:
  17. Alec_t

    SD Card Chip/Emulator

    I'm not surprised. Isn't the tech proprietary?
  18. Alec_t

    Need help designing / understanding this 'circuit'

    With a microswitch operated by flap movement there wouldn't be any need for wires on the flap.
  19. Alec_t

    Electric Ducted Fan Powered Longboard Help Please!

    I guess that would depend a lot on your engineering ability, and ability to source motors, gears etc.
  20. Alec_t

    3.85 V li-ion battery to replace 3 V lithium cell in bathroom scales?

    A fully-charged Li-ion cell could be 4.2V, so even with a dropping diode the voltage would be a tad high. Your scales would probably survive, though.
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