Require an indicator light to illuminate whenever a pivoting blade contacts a machine frame.
Blade is electrically isolated from the frame (a circuit wire can be connected to the blade).
Machine has a 24VDC power supply; however, a separate 12 or 24VDC supply will be used.
Circuit will operate independently of the machine’s PLC.
Circuit components:
1. Switch (metal contacts comprising a knife-blade closing on a machine frame).
2. Power supply.
3. Indicator LED.
4. Various discrete components.
In summary we need to use frame ground (not -VDC) to complete the circuit.

 

Not really sure what you're asking?

 

Does light need to remain on for any length of time?
Power supply neg. will be frame ground even if it is dedicated supply for light.

 

Does light need to remain on for any length of time?
Power supply neg. will be frame ground even if it is dedicated supply for light.

Thanks for replying.
No timer required (just on when blade touches frame)

 

Why can't you use the machine's 24vdc to power the indicator?

 

12 V supply + to 500 ohm resistor, 1/2 W red LED, anode to R, cathode to blade, frame to 12 -.

 

Why can't you use the machine's 24vdc to power the indicator?

Thanks . . .
We probably can but we wanted to keep it separate because it's not interfaced to the PLC.

 

12 V supply + to 500 ohm resistor, 1/2 W red LED, anode to R, cathode to blade, frame to 12 -.

Many thanks Bernard we'll try that.