nc reed switch wiring

[bilgekaan]

Hello,
I want to count rotating freq of an object using normaly closed reed switch.My circuit will be powered from battery , I detect the pulse when swicth is opened and I want to drive current only when switch is open.What is the correct wiring for this kind of switch?
Best regards,
Bilgekaan

 

[KMoffett]

Can you post the circuit your switch will be driving?

Ken

 

[bilgekaan]

Ken,
I have add some explanation on the circuitry.

 

[alexan_e]

In any case you need a pull-up or a pull-down resistor, this resistor (like the circuit you have posted) drives the input of the mcu to
gnd or Vcc when the switch is open.
I don't see a way to have no current flowing when the switch is on because then there would be no way
to change the state of the controller input when the switch is open.

If you want to limit the consumption use a high value resistor , 47k should work.

Alex

 

[KMoffett]

As Alex said, I don't see a way to make a NC switch draw "no" current in your case. Raising the pull-up value will help. An active p-channel switch can allow you to reduce the quiescent current even more. I have not bread-boarded this circuit (don't have that small MOSFET), but it should work.

Ken