By far my favorite creation is what I call the rainbow belt, it's a simple, efficient and reasonably robust way of packing 3 or more different item types onto a single belt
Rainbow Belt: Labs
How it works is as follows.
- The belt forms a loop
- A circuit wire is connected to the belt at the end of the loop right before the splitter.
- That connected belt is set to always allow flow, and "read contents, hold", its function is to detect items which are recirculating.
- The belts entering the splitters are wired to the detector belt and given conditions such as "Alien Science Pack = 0", meaning they only allow items to enter if those items are not recirculating, meaning they are being consumed.
The system handles all sorts of contingencies really well, like if one of the resource types dries up then the belt will generally not saturate, it will just end up with a smattering of the other types recirculating, leaving plenty of room for the missing type to enter when it becomes available again. It also deals well with uneven consumption, as whichever resource is consumed most will be allowed to enter the most.
Rainbow Belt: Science Pack 3
In this screenshot the output isn't being used much and it has backed up. The rainbow belt is wonderfully mixed up. Under clogged conditions the occasional spurt of resources will be allowed in, which is why there is banding (the banding is moderated by the action of the splitter). But when the resources are being consumed quickly all the resources will be allowed to enter simultaneously and will be mixed homogeneously - this is why a rainbow belt setup generally permits the full throughput of the belt to be used, if everything is being used it is perfectly mixed.
Rainbow Belt: Red Circuits (1 lane only)
One use of the rainbow belt is economizing on belts, another use is when you literally only have room for one belt due to beacons (note: I am religiously opposed to underground belt braiding).
In the case of advanced circuits resources are used in a 2:1:1 ratio, in such a case one lane can be dedicated - in this case the copper cable is allowed on unconditionally and the circuit belt logic is used to moderate plastic and electronic circuit inflow.
As I noted before, the rainbow belt setup is really quite robust. It handles things like being starved well, without saturating or jamming. (Note: In the above setup I used a filter inserter for each resource type, there's no particular reason, I was just trying something)
Count Perfect Mixing
A rainbow belt is a thing of terrible beauty, artistic, slightly chaotic, possibly evil. It probably drives some pedants loopy just looking at it (I on the other hand, love watching my rainbow belts).
But happily, I also have a count perfect system, once again with advanced circuits which use the handy 2:1:1 ratio:
This one uses an arithmetic combinator as a signal repeater to remember the count of items which have passed through the connected belts.
- Both connected belts are set to read belt contents in pulse mode.
- The plastic belt is set to "Plastic < Electronic Circuits"
- The electronic circuits belt is set to "Electronic Circuits < Plastic"
- The constant combinator sends a "Electronic Circuits = -1" signal to one of the belts to break the deadlock.
- Since either one belt or the other is always operating there is always a full belt of content entering the splitter.