A television on the shop floor lasts fourteen months

What came out of the housing

We took down a 55 inch consumer television from a metal parts plant in October, fourteen months after it went up. The back cover had a felt mat of aluminium dust about 2 mm thick over the vents. Two electrolytic capacitors on the power board were domed. The bottom 40 mm of the panel had a brown gradient that got worse after each shift. The plant manager was not surprised. He had already replaced one unit in the same spot and had a second one on order. Nobody had asked what the display was for, so nobody had bought the right object.

The TV was designed for a living room

Consumer televisions are rated for roughly eight hours a day at 25 C ambient, sitting still in a cabinet with clear air behind them. The vents are on the top and the back, which is precisely where dust falls. The back cover is thin plastic with no filter. The duty rating assumes the backlight is off half the evening. None of that is a defect; it is a design brief that does not include a shop floor. A commercial display is built around the same panel with a different brief: 16 to 24 hours a day, filtered airflow, a metal or thicker plastic chassis, and a rated ambient temperature that is written on the label rather than implied.

The light level is always higher than the estimate

Production halls run 500 to 800 lux on the floor. Under a canopy with skylights it climbs past 1,000 at midday. Welding bays and inspection stations with task lighting can hit 1,500 locally. A 350 nit panel in that room reads grey, and the first thing the operator does is turn the brightness to maximum, which shortens the backlight life and raises the panel temperature by another 8 to 10 C. For a general shop floor, 500 nits is the floor and 700 is comfortable. Ask for an anti-glare surface; the same 500 nits with a matte finish reads better than 700 nits on gloss, because the reflection of the roof lights is what makes numbers disappear.

Static numbers, and what they do to a panel

An andon board shows the same table all shift: line, target, actual, deviation. That is a fixed image, and a fixed image is what leaves a ghost. On the removed unit, the ghost of a KPI column was visible as a faint rectangle when the screen was showing white. Solutions in order of cost: run a pixel-shift function that moves the whole image a few millimetres every ten minutes; dim to 60 percent when the hall lights drop at night; and design the layout so the columns are not pure white on black for eight hours. A layout with a light grey background and dark text ages more gracefully than the reverse, which is the opposite of what most dashboard templates do.

Heat is the actual failure mode

A 55 inch panel dissipates 120 to 180 W, most of it as heat at the back. The power supply adds another 20 to 30 W. In a hall at 35 C, with summer peaks at 45 C near a furnace line, the air inside a closed enclosure reaches 60 C and the electrolytic capacitors age twice as fast. That is what domed the caps on the unit we pulled down. Two workable answers: a ventilated enclosure with a replaceable dust filter and two low-noise fans, or a sealed enclosure with a heat exchanger or heat pipe. The first is cheaper and needs the filter washed monthly. The second costs more and needs nothing. Choose based on whether the plant has anyone willing to wash a filter.

Getting the signal 60 metres

The control cabinet is rarely next to the screen. Passive HDMI cable is reliable to about 15 m, active copper to 30 m, and past that the failures start as intermittent sparkles that nobody reports until the whole picture drops. Three practical options: HDMI over fibre for a single source, HDBaseT if the run is already CAT6 and under 100 m, or an Android player mounted at the screen with the data coming over the plant LAN. The last one is what we recommend for KPI boards, because the network was going to reach the wall anyway and it removes the long video cable from the equation entirely.

What an operator can read from six metres

A 55 inch screen watched from 6 m: the characters need to be at least 30 mm tall for comfortable reading, which is roughly 90 to 100 pt. If the viewing distance is 10 m, double it or use a 75 inch screen. Three to five numbers per screen is the practical maximum. Red and green as the only carrier of meaning excludes the roughly 8 percent of men with red-green colour deficiency, so pair colour with a shape or a position. Refresh every 30 seconds, not every second; a number that changes constantly stops being read after the first hour.

Mounting it so it stays flat

Steel structure, forklift traffic, and vibration from presses. A fixed wall bracket with four M8 anchors into the steel is fine; a tilt bracket set 5 to 10 degrees downward keeps dust off the top edge and cuts ceiling reflections. Put a safety strap on the bracket regardless of the anchor calculation, and bring the cables in through a gland at the bottom, not through a hole drilled at the top where water and dust enter. If the screen hangs in a bay where a crane passes, add a protective frame; a single impact writes off the panel and the frame costs a fraction of it.

The line items that make the difference

Where to go next

Indoor digital signage LCD video walls