How do I reverse/convert a push to make (aka normally off) circuit?

[phexagon]

I have a circuit where I only have a momentary switch with the push to make (aka normally off) design.

It's normally off, when I push the button it closes the circuit and allows current through.

The wires it closes/opens are the two orange ones in a CAT5 cable so please bear in mind the low power involved. Is there any circuitry devices (mosfets or something) that will convert the on-off momentary function the button employs so it reverses to "normally on" as opposed to "normally off"?

I know, buy a "Normally on" momentary switch instead right? However the button I needs to be specific and they only come in momentary off(on) "normally off" states and is mission critical I use the buttons for aesthetic/design purposes.

 

[Joe G]

would comparator logic inverter work?

 

[phexagon]

Thx for the tip, I don't know, I'm asking.

My google fu is weak and offers little help on those on top of not really understanding the schematics.

Maybe someone can link to a component on ebay which might do the trick. Please note the low current of a single strand in a cat5 cable involved.

 

[4pyros]

My google fu is weak

Sorry I have no idea what that is?????
What voltage is the switch switching?

 

[Dr_Doggy]

prolly easiest to hack the button, you need to find the voltage across the open button and current through the closed button to be safe,
you could use an inverter circuit

 

[Joe G]

data sheet=microchip=MCP6541 on page 12 and others such as LM339 comparator or even google "comparator logic inverter". sounds like it might just work for ya'

 

[4pyros]

hay how about a relay?

 

[dougy83]

Are you just switching DC for signalling? If it really is low power, and it doesn't matter if the switch drops a volt or so, you can use a BJT (transistor) turned on using a large resistance between base and collector, and turned off by the switch between base and emitter. You should also connect a small capacitor between base and emitter to reduce noise pickup.

 

[eTech]

Hi

I'm curious as to the signal you are switching thru the button.

What kind of signal?

eT

 

[Reloadron]

Can you post the circuit? I have no idea what is going on?

The wires it closes/opens are the two orange ones in a CAT5 cable so please bear in mind the low power involved.

This means what? Simply light gauge wire is used?

Ron

 

[Misterbenn]

Whats on the other end of the cable? You might be able to leave the switch alone and just change the circuitry at the other end.

Use an inverter is this is just signal on/off, i.e a signal back to the power supply to turn on/off (like the power button on a pc)
use a relay or FET if this is a power on/off, i.e the full device current flows through the switch (like a light switch)