Converting NO to NC

[Braren]

Hi,

I have a project I'm working on and basically I have a controller that runs a DC power Tool, and this controller also has some limited IO functionality. One Input function is "Lock Tool" which will stop the tool from running if it is running, or prevent the tool from running if it isn't already. Unfortunately, this controller does not have a "unlock tool" function paired with a tool normally disallowed condition; which is why I need to convert the NO sensors (prox and servo) to NC.

This is how the system currently works...
1) Operator presses DI3 button/switch (not yet on schematic)
2) DI3 input triggers DO1, which turns on the servo, which engages a pneumatic brake.
3) When the brake is engaged, the Proximity sensor and Servo Sensor will pass a signal to DI1 and DI2 respectively.
4) The Tool is now locked by the two digital inputs (the tool will run before the brake is engaged)

This is how I want the system to work...
1) Operator presses DI3 button/switch (not yet on schematic)
2) DI3 input triggers DO1, which turns on the servo, which engages a pneumatic brake.
3) When the brake is engaged, the Proximity sensor and Servo Sensor will NOT pass a signal to DI1 and DI2 respectively.
4) The Tool is now unlocked by the two digital inputs (the tool will NOT run before the brake is engaged)

So all I need to do for this to work how I want is something that will convert the two NO sensors to NC. Can this change be made with a relatively simple circuit? Will this be a robust solution (I don't want intermittence or components to fail often)? What would this circuit look like? As you can see on the diagram below, I have a 24V power supply readily available.


Thanks in advance for the help!

[helenamaurya]

Anybody remember the loop converter that was available for NO floor mats to
allow for their use on NC loops? Part number? Name?

I need to trip a NC loop with an NO device.
Relay is no good, battery operated.