LED Button push light up

Maybe you can use addressable LEDs

https://www.makerguides.com/how-to-control-ws2812b-individually-addressable-leds-using-arduino/

It will save a lot of DIY'ing too, since they already come in strips (e.g. mount behind clear plastic, and have printed card on front), and it would be a pain to wire up 21 LEDs to a board.

This might be the quickest way.

Pixel strings may be alternative to pixel strips.

12mm Diffused Thin Digital RGB LED Pixels (Strand of 25) - WS2801:
https://www.adafruit.com/product/322

beacon_dave said:

Pixel strings may be alternative

Great find! Adafruit has excellent examples and tutorials to go along with them too - and it looks like it only needs 2 pins to make it work.

Would it be able to be wired to light up one at a time?  And then after 21 shut off all lights. 

Yes. On the face of it, based on what you have stated, those addressable products (either a strip, which might be a bit cheaper, or the pixel strings which might look better, would meet your need, and would be perhaps the easiest and quickest way to achieve it. They are often known as 'neopixel' if you wish to search for it.

They will work with pretty much any Arduino board, or even Pi Pico board, depends on your preference. If you google the board name that you choose, along with the text "neopixel" you'll find plenty of example code to control individual lights. The link that javagoza and beacon_dave have provided would be good examples to start with.

Thank you for your help. 

If you look toward the end of that Makerguides article that javagoza linked to, it tells you how to change a single LED in the pixel LED strip.

Look for: "How do you control individually addressable LEDs?"

You can set the red, green, and blue values of each LED independently.

This is super helpful 

More documentation on the FastLED library here:

https://github.com/FastLED/FastLED/wiki/Basic-usage

ralphjyrecently tested a very interesting product that consists of a matrix of 10x10 addressable rgb leds that come unconnected and that can be very useful for a project like this, being able to use one or more leds for each score unit depending on the intensity of light that you need. And since they have to be wired, you decide the distance between each LED.

(+) NeoPixel Dice - Ralph Yamamoto's Blog - Personal Blogs - element14 Community

Well remembered ! Adafruit do something similar using their Flora pixels if you want something a bit larger to work with.

https://www.adafruit.com/product/1559

It is not clear though if the design of the scoreboard is already finalised or not. If it is a retrofit to a typical vertical style scoreboard then the LED strip spacing will need to be close enough to that of the spacing of the numbers already printed. The strings may be easier to work with than the tapes.

Some scoreboards have holes for pegs, so not sure if the intention is to try and stick a LED into an existing peg hole, so a round LED of suitable diameter may work better than a square pixel.

Also not clear as to the number of scoreboards involved. If it's a one-off, then hand soldering the 42 LEDs isn't much of an issue. If it is 10+ then pre-wired strings/tapes may start looking like a good plan.  

Well remembered ! Adafruit do something similar using their Flora pixels if you want something a bit larger to work with.

https://www.adafruit.com/product/1559

It is not clear though if the design of the scoreboard is already finalised or not. If it is a retrofit to a typical vertical style scoreboard then the LED strip spacing will need to be close enough to that of the spacing of the numbers already printed. The strings may be easier to work with than the tapes.

Some scoreboards have holes for pegs, so not sure if the intention is to try and stick a LED into an existing peg hole, so a round LED of suitable diameter may work better than a square pixel.

Also not clear as to the number of scoreboards involved. If it's a one-off, then hand soldering the 42 LEDs isn't much of an issue. If it is 10+ then pre-wired strings/tapes may start looking like a good plan.  

I am planning on drilling holes for the bulbs to go in. And the light next to the score to be lit. After 21 points I want it to have all lights go out on the next button push.  Once I have that figured out I need to do it for both sides. 

Perhaps create a variable to hold the button press count.

Each button press increments the count variable by one.

Then check the current value of the count variable.

If it is less than 1 then turn off all the LEDs. 

If it is between 1 and 21 then turn off all the LEDs and then turn on the LED that matches the current count value.  

If it is greater than 21, then turn off all the LEDs and then reset the count back to 0.

For the second side you just need a second counter that gets incremented by the second button.