Output State on Power Off

[ccdubs]

Thanks for the suggestion.

One last question. Where is the low impedance path from +24V to GND coming from? Is it the power status LED only? If so I could cut this and/or its resistor off.

[support]

Officially I wouldn't recommend it - but you could try this: bend out the pin #9 of the ULN2003A which is the diode connection to the +24V. Since it is socketed you can just remove the IC, bend out the pin 9 so that it doesn't enter the socket, then insert the IC back to the PLC.

[ccdubs]

Hi Support,

Regarding this thread from over a year ago, I notice in the latest batch of PLC's that one of the referred chips (ULN2003A/ULN2803A) has been replaced by a different chip.

Is the disconnection of pin #9 still valid?

[support]

If it is T100MD888+ there wasn't any change in the hardware design in the last few years. The ULN2003A are quite common chip and produced by a number of different manufacturers. A different brand may have been used which you may mistake as being a different chip, but the part number should be the same.

[ccdubs]

With regards to the thread below...will the FMD series PLC's need the same pin 9 modification?

[support]

The ULN2003A and ULN2803A are designed into the FMD88-10 and therefore subject to the same characteristics. There is still the built-in diode to protect against inductive kick.

[ccdubs]

Support, can you please tell me which chip is connected to which outputs?

[support]

For current FMD88-10 design, output 1 to 4 is controlled by UU2 (ULN2803A). Output 5 & 6 by UU3 (ULN2003A). Output 7 and 8 are by  T1 and T2 (IRLU024).