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:
MPF tries to make this right for you and your can configure those LEDs as follows:
number: 0 # first LED in chain (with three channels) - exact number format depends on your platform
number: 1 # second LED in chain (with three channels)
There are also RGBW LEDs which are compatible which usually use RGBW as order. They can be used like this:
- number: 3-0
- number: 3-1
- number: 3-2
- number: 4-0
Starting with MPF 0.54 there is a new syntax to chain LEDs:
start_channel: 0-0 # the exact number format depends on your platform
type: rgb # will use red: 0-0, green: 0-1, blue: 0-2
type: rgbw # will use red: 0-3, green: 0-4, blue: 0-5, white: 0-6
type: rgbw # will use red: 0-7, green: 0-8, blue: 0-9, white: 0-10
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
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.
"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.
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.
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.
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.
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.
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 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.
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