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WS2811 and WS2812 LEDs in Pinball

The most common serial LEDs use WS2811 or WS2812 controllers. Both controllers differ in the order of the channels. The WS2811 controller uses RGB and WS2812 uses GRB order. Unfortunately, some controller (i.e. Fadecandy) expect WS2812 by default and shuffle pixels internally for you.

Overview video about serial LEDs:

Config

MPF tries to make this right for you and your can configure those LEDs as follows:

lights:
  my_ws2811:
    number: 0         # first LED in chain (with three channels) - exact number format depends on your platform
    type: rgb
  my_ws2812:
    number: 1         # second LED in chain (with three channels)
    type: grb

There are also RGBW LEDs which are compatible which usually use RGBW as order. They can be used like this:

lights:
  my_rgbw_serial_led:
    channels:
      red:
        - number: 3-0
      green:
        - number: 3-1
      blue:
        - number: 3-2
      white:
        - number: 4-0

Starting with MPF 0.54 there is a new syntax to chain LEDs:

lights:
  led_0:
    start_channel: 0-0    # the exact number format depends on your platform
    subtype: led
    type: rgb    # will use red: 0-0, green: 0-1, blue: 0-2
  led_1:
    previous: led_0
    subtype: led
    type: rgbw   # will use red: 0-3, green: 0-4, blue: 0-5, white: 0-6
  led_2:
    previous: led_1
    subtype: led
    type: rgbw   # will use red: 0-7, green: 0-8, blue: 0-9, white: 0-10

Hardware

Each pixel connects to the next pixel with three wires: VDD, signal, GND. According to the datasheet VDD should be 4.5V to 5.5V. This means two things: First, you can safely dial to power supply up to 5.5V for serial LEDs and we recommend you to do so. Secondly, you should make sure that at maximum brighness (i.e. maximum power consumption) the voltage should not drop below 4.5V. We urge you to actually test this by dialing the brightness up the maximum and measuring the voltage at the middle and the end of your chain.

What if the voltage drops below 4.5V? From our experience serial WS2811/WS2812 work down to 3.5V but the whitepoint shifts to more blueish and the chain becomes much more susceptible to noise and flickering. If you see the voltage below 4.5V we strongly suggest that you fix your power setup.

First step should be to connect power from both sides to your chains. That does not harm and practically halfs the length or your chain. Afterwards, measure the voltage in the middle of the chain. If that still does not help try using thicker wires or dialing up your power supply (especially if the voltage is also dropping at the beginning of your chain).

If all this does not help try shorter chains. Most controllers support multiple chains and you should take advantage of that.

Do not underestimate the currents which are needed to drive LEDs. As a rule of thumb you can calculate 60mA times the number of LEDs. If you got 100 LEDs that make it 6A. 300 LEDs result in 18A which at 5V are 90W. Size your power supply accordingly. Also remember that the voltage drop in your wires is resistance times current R * I so size the wire between your PSU and your lights accordingly. You can check this using the Voltage Drop Calculator. Also note that standard .156 molex connectors are only rated for 7A and you do not want your board look like WPC boards with burned connectors.

Video about electronics basics:

Video about wiring of lights:

Types of LEDs

Single Chip LEDs

Those while small LEDs are in a 5050 package and often used on PCBs. All those light rings, stripes or any PCBs are most likely WS2812. FAST pinball sells PCBs which can be mounted below an insert and there are numerous other designs to buy around the internet.

TODO: Add a picture of WS2812 PCB

Christmas Lights

"Christmas Light" chains are very well known. You can buy them for around 15 bucks with 50 lights. Those work well for GIs but you can also use them below inserts if you print or bend holders for this.

image

Those LEDs are WS2811 in most of the cases. You typically see the controller as a separate chip and a RGB LED soldered to it.

Bulk WS2811

You can actually buy WS2811 in bulk from China. They are usually used to build christmas light chain but you can solder almost any LED to them. This could be flashers, custom playfield lights, segment displays or any other light you want to control. The chip will provide around 18.5mA per LED at full brightness.

TODO: Add a picture of a WS2811 PCB

Some of those controllers also support 12V power supply. The datasheet is inconsistent here. Absolute maximum rating are 6-7V but they also talk about 12V and 24V. So take care about that voltage when buying those PCBs.

WS2814 or SK6812

There is not much known about the inner working of those chips. But they work similar to the chips above but at 18.5mA * 4 = 74mA total power.

TODO: Add a picture of a RGBW WS2814 and/or SK6812

WS2813

Those chips are similar to the WS2812 chips but they got an additional fallback input which connects to the output of the second last LED. If the previous LED in the chain breaks the chain will continue to work which is very convenient.

TODO: Add a picture of a WS2813

There exist four versions: * A and B run at 18mA * 3 = 53mA (similar to WS2812) * C and D are low power version und run at 5mA * 3 = 15mA

WS2815

WS2815 is a 5050 chip similar to WS2813 but it runs at 12V instead of 5V which is pretty interesting for pinball machines. This allows longer chains and thinner wires which is a huge improvement. Additionally, it has the handy fallback pin of WS2813 so one broken chip will not bring down the whole chain.

TODO: Add a picture of a WS2815

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