Oversized 7-segment display

[TomHoward]

Evening all

 

I am hoping for some ideas for oversized 7-segment display.

At work we are looking at building an in-house cricket scoreboard, that takes data from a widely used app over bluetooth and displays data.

The bluetooth / app / programming side looks all sorted but I'm wondering about how to make the giant 7-segment displays needed. I'm hoping to make them as units so I can swap them out / wire as needed so they can be swapped and repaired on the bench rather than on the scoreboard.

If this project takes of we may make ones of different sizes so something modular would be good.

 

 

The ideas I have at the moment are:

 

Use LED strip and transistor drivers to make the shapes

Use WS2812 tape and custom controller and drive them 10px at a time or so to make 7 segments.

Laser / CNC cut a load of holes in a piece of thin material and push through-hole LEDs through and wire them up bending the legs over.

 

Then to waterproof them:

 

Fit a perspex top

Make a back plate with a ridge and pour clear resin over the top to cover the tape / LEDs and set it in resin somehow avoiding air bubbles

 

The aimed size is about 30cm high x 15cm width.

I'm imagining with LED strip in either type it would be multiple strips to an edge.

 

Thanks for ideas!

[mikienorth]

There's 320x160mm display panels in single colour, and I think made for outdoor use, on ebay. I've no idea if they'll work for you, or even if it's a solution, but might end up cheaper than trying to reinvent the wheel... They're a tenner each.

Failing that, maybe see if there's anywhere that disposes of old petrol station signage?

 

Your post piqued my interest so I've been casually googling away to pass the evening...

 

https://www.ebay.co.uk/itm/LED-Module-P10-LED-Display-Outdoor-Module-RED-320-160-mm-LED-Sign/193217393756?hash=item2cfca7745c:g:xUwAAOSwwlJd1HvD

[timsabre]

The LED screen matrix modules as you've linked to are quite difficult to drive as you have to keep a scan going yourself. Though there are a few projects out there using more beefy arduino such as teensy.

[alistermorton]

If I was feeling lazy I'd use lengths of tape to make the segments, drive them with FETs and use a microcontroller to do the decoding and driving, You could do segment multiplexing to cut down on the control channels required.

[timsabre]

Plans here for 3d printed segments and couplers to form the digits. He uses WS2812 pixel tape to illuminate but you could also just use normal tape. Less connections needed for the pixels though.

https://www.thingiverse.com/thing:2977443

video of him making it here

 

[TomHoward]

Thanks for the pointers,

 

I am thinking currently of using LED tape as suggested, but rather than printing segments and enclosing it I am thinking of using it bare on the surface and maybe pouring resin over it to encapsulate it.

 

At the moment I am having the same thoughts about 'analogue' LED tape vs WS2812 tape.

With 7 segment tape, the first 9-digit display would be 63 segments, so that's a lot of cabling with traditional tape and 8 cores to each figure.

 

WS2812 / WS2811 tape might be much easier as only 3 core wiring all around the piece and it can daisy chain, but needs some more software but much lower component count as well as shouldn't need the transistors etc for switching.

 

This example uses bare tape, and the commercial units we have at the moment are bare thorugh-hole as well, which I'm also considering but more work

[timsabre]

Really don't do bare through hole LED's with free wiring. Once did that to make an exhibition stand for someone. It took what seemed like forever and despite getting the holes CNC machined it still looked wobbly.

I think now pixel tape is so cheap that has got to be the best way, but make sure you get 60 led/m version or the leds will be too far apart to merge into a line.

 

[bigclive]

Whatever you use, make sure it's serviceable. Water will always find a way in, and LEDs don't always last as long as expected.

[sunray]

Dont encase in resin as the LEDs have lenses on them and clear resin will totally negate that. You will end up with almost invisible miniscule spots of light.

 

 

 

 

 

 

 

 

Don't ask.

 

 

 

 

EDIT: I think I remember someone else on here makimg the same comment.

Edited March 4, 2020 by sunray

[alistermorton]

bigclive mentioned the effect in his video about making an XLR DMX monitor.

[timsabre]

That's true for lamp-style LEDs which have lenses. For the flat surface mount 5050 type there is no lens so it makes no difference.

[sunray]

That's true for lamp-style LEDs which have lenses. For the flat surface mount 5050 type there is no lens so it makes no difference.

No lens? I'm surprised, I've only handled tape a couple of times but the SMT LEDs I've used have lenses and assumed tape used the same devices.

 

What makes them directional?

Edited March 4, 2020 by sunray

[timsabre]

That's true for lamp-style LEDs which have lenses. For the flat surface mount 5050 type there is no lens so it makes no difference.

No lens? I'm surprised, I've only handled tape a couple of times but the SMT LEDs I've used have lenses and assumed tape used the same devices.

 

What makes them directional?

 

Well they aren't really directional. The output angle is probably 120 degrees or more. They just have a flat window with the LED die slightly recessed behind it. A lot of the high powered ones are the same, a separate lens or reflector is placed on the flat window to control the light.

[gyro_gearloose]

I haven’t used the stuff myself, but LED NeonFlex looks it should do what you need.

[TomHoward]

Thanks for the pointers. I was going to use through hole as I thought it would be neater than strip, but thinking about how many of these I've got to make I'm going to go with the minimum work per unit and try addressable WS281x tape stuck into 3D printed housings, then just power & data for each unit rather than having to do 8 wires.

 

As these are going to be outside for a long time, I don't know if the print material will matter - I don't want to be remaking them in a year if they've fallen apart..