Mixing 12/24 VDC on T100MD888

[Terry]

Does anyone know if the PWM outputs (7& are isolated from the MB system voltage?

I have a 24 VDC supply for the processor and motherboard, but my pump is 12VDC.  I'd like to drive the 20W pump directly from the PWM output (well within the rating) without the need for some intermediate device.  I thought I could feed 24 V to the power terminals and then use a separate 13.6 VDC supply (+ to the motor, return from the motor to Output 7 and then HIGH GND back to the separate supply.  

Will this work or will I have a melt down?

[support]

The PWM outputs are not isolated.

You can however use the T100MD888+ PWM output to drive a load with lower high side supply (12VDC in your case) if  you connect a diode in series from the load low side terminal back to the PLC output. This will prevent the output LED from being turned on by the current flowing into the 12V supply from the PLC's 24V supply.

     PWM    o -----|<|------[Load]--------o +12V
    Output

[evanh]

No need to have a separate 12 volt supply to the pump.  Simply limit the output pwm to 50% max for a 24 volt supply.

And do put a circuit breaker in.


Evan