For the Siemens Safety display, we needed a clear way to explain what state the system is in, and what specifically is faulted. What better way to show this than to use the Banner SD50 with discrete inputs. This configuration gives us 15 customizable states, depending entirely on the combination of which 4 input wires have an applied voltage.
In this article, I am going to explain a quick programming trick to easily map out your machine states, how that trick helped us troubleshoot our logic, and the hardware hurdles we overcame to integrate solid-state safety signals.
The 1-15 Programming Shortcut
Identifying the exact binary logic states for 5-wire control could involve a lot of tedious truth-table math, but I took a much faster and easier approach.
I initially connected the SD50 to the Banner Pro Editor Kit, then used the Banner Pro Editor software to simply name all the states 1 through 15. Then, I wired the display into the demonstration board and physically triggered each scenario (pressing the E-Stop, breaking the light curtain, tripping the overload). Whenever a fault occurred, I just marked down which number appeared on the screen, so I could later use the Banner Pro Editor software to rename those states to match what I wanted it to say.
Here is the real beauty of this method: I highly recommend only renaming the states you actually end up using. While testing the board, other people were messing with the switches and triggered a fault condition I would have never thought to test. Because I left the unused states as basic numbers, I instantly knew exactly which logic inputs were unexpectedly active just by looking at the number on the screen. The easy thing with the SD50 is I can easily plug it back into the Banner Pro Editor Kit, update my changes, hit write, and plug it back into my system.
For a full overview of the Banner Pro Editor Kit and software, check out the APDahlen Article: Introduction to the Banner Engineering SD50 Industrial Status Display Introduction to the Banner Engineering SD50 Industrial Status Display
Troubleshooting the OSSD Flicker
Having the display explicitly call out its logic state also became a massive asset for troubleshooting. While triggering different faults, I noticed one specific numbered state was causing the display to flicker dimly.
This led me directly to a unique hardware challenge with our light curtain. The SD50 can natively accept the solid-state OSSD signal from the Banner light curtain, which is a huge advantage. However, there is a catch: the display cannot be powered solely by an OSSD signal. Because OSSD outputs use continuous microsecond test pulses (briefly dropping to 0V to check for shorts), a display running on that signal alone will flicker. If left like that for a prolonged timeframe, it will likely suffer hardware damage.
For more info on OSSD signals, please check out the AP Dahlen article detailing the OSSD waveforms and how safety relays interpret them: OSSD Safety Signals: What the Waveform Tells a Safety Relay
The Relay Workaround
I could have easily solved this by using the light curtain to trigger a standard relay, and then used those dry contacts to send a continuous 24V signal to the display. However, I specifically wanted to demonstrate that the SD50 is capable of taking that OSSD signal directly.
To fix the flicker while keeping the direct OSSD connection, I needed to ensure that whenever the light curtain was tripped, at least one other logic input on the SD50 was also receiving continuous 24V power. I used our Siemens 3SK1211-1BB00 expansion relay to essentially flip a couple of other inputs on the display at the exact same time.
This created a brand new, distinct numbered state that provided the continuous voltage needed to run alongside the OSSD signal, completely stabilizing the display. While this is not a normal industrial use case, it was the perfect workaround to ensure every single state was covered for this visual demonstration.
The Final Configuration
Once the logic was ironed out, I just plugged the display back into the programmer and set up the custom text and color patterns for our specific scenario numbers. In the end, we utilized 7 of the 15 available states.
Hardware Used
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Banner SD50 (Discrete 5-Wire): 2170-SD50P300WD15QP-ND
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Banner Pro Editor Kit: 2170-PRO-KIT-ND