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Remote LED Annunciator

By Jim Rowe

IN THE BAD OLD DAYS, anyone rolling up at a department-store deli to buy a few slices of salami or whatever had to muscle their way through the crowd and try to attract the attention of a salesperson or they’d never get served. It was much the same at employment offices and medical scanning departments, where the rudest and most obnoxious people were often attended to first.

Things became more civilised when many of these places brought in systems to ensure that everyone was seen in the order of their arrival. In most cases, these systems use numbered tear-off tickets in a dispenser, plus a LED display or "annunciator" unit which can display the numbers from 00-99 and can be updated to show the next customer to be served. It’s a simple system but it works well.

LED annunciators are available commercially but they’re not cheap. So if have been put off by the price tag, this project is for you. You’ll be able to assemble it from a kit for much less than you’d pay for a similar commercial unit.

Main Features
Number Range: 00-99 - incremented by one each time a button on control box is pressed. Built-in piezo buzzer to attract customer attention.

Readout: two 75mm-high digits using high-brightness LEDs.

Power Supply: 12V DC plugpack (display unit supplied via cable from control box).

The LED Annunciator has digits 75mm high, each using 28 high-brightness 5mm red LEDs so they’re clearly visible from many metres away. The number displayed – from 00-99 – is incremented simply by pressing a button on the separate small control box which can be located at any convenient place behind a counter or reception desk.

The Annunciator has no memory, so when you turn it off and then back on next morning, it comes up with a display of "00" rather than the last ticket number used the day before. However, it’s easy to "run it up" to that number because there’s a built-in self clocking function. You activate this simply by holding down the button for about four seconds and then only releasing it when the display reaches the number you want to start with.

The unit also has a built-in piezo buzzer, to produce a short "beep" each time the display is updated, to attract customer attention. However, this can be disabled with a switch if you find it too irritating.

The whole thing runs from a low-cost 12V regulated plugpack, although those in rural areas could run it from a 12V battery if they wish. The power feeds into the small control box, which then connects to the display unit via a standard telephone extension cable fitted with RJ12 connectors.

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