Outdoor LED Screen teardown (+how to drive LEDs with video)

A look inside a large outdoor LED screen, including detailed technical analysis of drive techniques for LED video displays.

Category:

Science & Technology

Tags:

• led
• screen
• teardown
• pwm
• driver

[bigclivedotcom]

Very interesting. I wonder why they're changing it, since it isn't all that old. That said, the advances in LED panel technology over the past few years have been staggering, so the new display will probably just use off the shelf Chinese panels. I used to do the servicing on the vintage Scannervision display in Glasgow which used filament lamps with RGB filters in front of them to produce a low resolution colour display. The lamps were 12V xenon gas filled tungsten and switched with triacs.

[mikeselectricstuff]

@bigclivedotcom I guess LED wear-out - apparently it was originally installed 10 years ago, and had the panels replaced about 5 years ago. Olympics probably the excuse to replace. Don't know what they replaced it with, but doubt they'd risk cheapo panels for a high-rent location like this! 

[coondogtheman1234]

Very interesting stuff. So is this unit yours to keep or do you need to return it? Also Is it possible to input an analog composite video signal via RCA connector into one of these units or a full screen? If so I could hook up a video game system to a display like this.

[mikeselectricstuff]

@coondogtheman1234 These were custom made for the London site, and not very useful for anything else, which is why I got one. You can't display normal video without a lot of pre-processing to format the data.

[coondogtheman1234]

@mikeselectricstuff

isn't there a box or something that can convert the analog video to the format required by the array?

[mikeselectricstuff]

@coondogtheman1234 Yes. I suspect it's very expensive - if you can afford 6-7 figures for a big screen installation, 4-5 figures for the control box is small change....

[unomasenelmar]

Wonderful, sublime, masterful explanation of his handling of an LED screen.

I think the design could be simplified, for example by integrating the LED driver and controller on the same panel LED will avoid excessive cable lines.

Congratulations for the job to explain and give these wonderful videos.

Greetings from Argentina.

Thank you.

[bigclivedotcom]

@mikeselectricstuff I didn't realise it was ten years old. Time flies. The mass produced Chinese panels are not necessarily low quality things (I'm sure there are some though), LED video walls are so common now that a wide variety of breathtakingly slim and light panels are now available in surprisingly high resolutions. Ever go to PLASA at Earls Court? They always have a load of different systems on show, and it's rare to find any LEDs out on them these days.

[MMGWsceptic]

@mikeselectricstuff Seconded. The LEDs in this product are driven at about 20mA to get 5000cd/m2 brightness. LED efficiency and lifetime drop with currents so even with 4:1 mux you may need > 100mA peak current to achieve the same brightness (since you'd have 1/4 the time to light up each LED). So the muxd LEDs would die quick. Also - the drivers would get too hot since they'd be pumping out 100mA all the time.

[danalee1000]

I had no idea these were as complex as that, with regard to brightness levels. I just figured it was mostly pulse modulation. Thanks for another terrific teardown, Mike!