We were requested to provide a proposal for a visitor polling kiosk. Essentially, there would be a question with three or four multiple choice answers that the visitor could select from. Once they made their selection, the display would show bar graphs representing the percentage of visitors that selected that answer as well as display the actual number of visitors with that answer. This was a great idea because if the kiosk were designed so the graphics could easily be changed out (the questions and answers), this kiosk could be updated periodically to reflect the current hot topic and trends. In other words, it was no longer a static exhibit but would probably be different on each visitor’s re-visit.

The requested proposal was not for LEDs but rather for motorized bar graphs and airline terminal flip type digital displays. We did not provide a proposal because we believed the requested technology, although really cool, would be a museum maintenance nightmare. But, we like the idea enough that we designed a similar kiosk using LEDs bar graphs and 7-segement numeric digits as the display.

We used our LED Commander Series for control of the LED bar graphs and feedback in the illuminated buttons. Each answer had its own color (green, yellow, red and blue). The bar graphs were 25 bar segments, each with four LEDs making up the bar. That is a total of 100 LEDs plus the four LEDs in the illuminated buttons that were being controlled independently. We then designed a six-digit, 7-segment system to display the actual poll quantities. These systems were controlled by TTL RS232 strings (from the LED Commander) and the six digits were multiplexed to save on current. Multiplexing ensures only one digit is illuminated at a time but it is done so fast that the persistence of the eye does not detect when it is off. You can see the behind the scenes electronics in the image below.

Here are some other details our version of this exhibit. First, the maximum number of visitor votes that can be counted before a roll over has to occur is 3996. And that is only if the visitor answers are equally distributed. The original proposal wanted the kiosk to totally zero out whenever one of the answers totaled 1000. We were not inclined to this approach. So our logic divides each tally by 10. In this way the bar graphs will remain in the historical ratio they were before the rollover. Obviously, there is no way to make follow-on additions to be weighted for the historical ratio, but we think the exhibit rollover will be more seamless to the visitor.

We provided a hidden button to zero out the exhibit for whenever the question graphics are changed out. Upon power up, the exhibit goes through a little diagnostic routine allowing the museum staff a way to verify all the LEDs are operational and see the current tally.

The tally, if changed, is stored once every hour while the system is on into non-volatile memory so when it powers up after a shutdown it will have pretty close to the last statistics. We don’t update the memory more often in order to avoid wearing out the compact memory flash in the micro-controller which has a constrained number of re-writes. We estimate that even in a 24/7 operation, the memory should last at least five years.

Finally, in the requested proposal, it was desired that the exhibit would always show the current statistics. We don’t think that is such a great idea because it tends to bias the visitor into ensuring his poll is in line with the majority at that time. So our version has a little attract sequence while waiting for visitor input. The bar graphs oscillate up and down and the digits reflect a moving dash through them (and all the buttons are illuminated). Once a button is pressed, the display stops the attract sequence and reflects the current data with only the last button pushed being illuminated. It shows this information for about 15 seconds (a time we can change) at which time it returns to the attract sequence.

If this type of exhibit is of interest to you, please contact us so we can discuss your requirements and provide some pricing.