sp3t switch and diode oring my circuit. Do I understand?

Hi everyone,
I’d like to add an additional feature to my projects. Instead of a simple SPDT switch for on/off, I’d like to use a sp3t to have OFF, ON, and ON with an additional feature like sound, for instance.

Refer to the attachment, but it’s also described here:

I would have a battery positive going into the spdt, with no output on the 1st switch state, output to vcc on the 2nd state (so the circuit turns on normally) and the 3rd state would be outputing:
FIRST: to a transistor that turns on control over the piezo buzzer, so sound is on.
SECOND: would then go through an ideal diode that goes to vcc, powering all of the project with ideally a very minimal voltage drop. (this would make sure that VCC wouldn’t go through the diode to power the piezo buzzer when the SP3T is on its second state)

I was first of all wondering if this makes sense, and if it does, what component would be logical to use here? a normal diode drops too much current, maybe schottky diodes, I know they are used for diode oring and are pretty cheap on ebay. But I know they can still drop voltage for 0.3v or so, and therefore waste power too, plus have leakage current whenever my device is on the second state of the switch (ON but no buzzer). Is it viable to feed a whole 5v circuit with lets say around 100-200 mA current from a schottky diode? Or I heard about parts like the MAX40200, which is supposed to beat the schottky’s downsides. Would something like this be better?

BONUS: if I decide to add V regulation to this circuit, where should I put the regulator? I was thinking both ON sp3t states could output into the regulator, which would ouput into the rest of the circuit. That would mean the base of the piezo’s transistor would not be regulated, but this probably isn’t a problem right?

Thanks everyone!

Use a DP3T switch, with one pole for Vcc and one for the buzzer.

There may exist better and more stable solutions, but your description is a bit vague for better suggestions.

You may have a problem going from the 2nd to 3rd position of the switch, because VCC will momentarily drop out while the switch is between switch contacts.

DrDiettrich:
Use a DP3T switch, with one pole for Vcc and one for the buzzer.

There may exist better and more stable solutions, but your description is a bit vague for better suggestions.

Im not sure I understand. So that means you would have the battery either going to VCC or the buzzer, but never both at the same time?

david_2018:
You may have a problem going from the 2nd to 3rd position of the switch, because VCC will momentarily drop out while the switch is between switch contacts.

This is not a problem. I wanted the user to be able to turn on or off the sound, but not play around with this switch while the device is already on. and if power turns off for a few seconds, I dont mind if the program resets on the Arduino for instance.

The buzzer and Vcc are connected independently to the battery.

Step back a bit...

  • Power +V on common slider,
  • Processor Vcc on first,
  • Input pin X on second (with diode poiniting back to first position).

10K Pull-down from second position to 0V

  • Switch off = off. (pin X can float if it wanst to - the CPU is off)
  • Switch #1 = cpu on, pinX pulled 0V
  • Switch #2 = cpu on, pinX driven +Vcc

Program looks at pinX to determine whether to play sounds or not.
(Leaves the possibility that sound can be 'forced' if neccessary - e.g. low battry warning, critical error etc)

lastchancename:
Step back a bit...

  • Power +V on common slider,
  • Processor Vcc on first,
  • Input pin X on second (with diode poiniting back to first position).

10K Pull-down from second position to 0V

  • Switch off = off. (pin X can float if it wanst to - the CPU is off)
  • Switch #1 = cpu on, pinX pulled 0V
  • Switch #2 = cpu on, pinX driven +Vcc

Program looks at pinX to determine whether to play sounds or not.
(Leaves the possibility that sound can be 'forced' if neccessary - e.g. low battry warning, critical error etc)

At first, I wanted to try this so its a hardware feature and no software involved. Your solution is cool, because it's a mix of hardware and software to set the sound. But that would mean that my solution with the diode and transistor would work too, right?

I am really wondering what diode/component would you be using? a mosfet, a schottky, something else?

Because you aren’t drawing much current, something easily available - like a 1N400x will be plenty.

If the 0.6V drop is an issue, use a schottky diode (0.2V drop).

The T in MOSFET, stands for Transistor (not a Diode).

There are a lot of options in the design, depending on specifics you are aiming for. Bake the cake first, then play with the icing.