Your bot tracks a straight line just fine.

Most builders still default to the bigger array anyway, assuming more channels can only help. Extra channels you don't use still add weight to the nose of your chassis and current your power rail has to supply, whether your track asks for them or not.

The right sensor follows your track's geometry, not the spec sheet. Here's what actually changes between 8 and 16 channels, and where that extra resolution starts earning its keep.

If you're still weighing this against an actual event date, the Techgeeks community has builders comparing exactly this trade before their own runs.

What actually changes between 8 and 16 channels

The ARC8 reads all 8 sensors directly, one microcontroller pin per channel. The ARC16 reads its 16 sensors through a multiplexer: four select lines pick a channel, one line reads it. That means the ARC16 needs six microcontroller pins total, two fewer than the ARC8's eight, despite carrying twice the sensors.

What you do pay for is weight and current. The ARC8 weighs 3 grams and draws about 150mA. The ARC16 weighs 8 grams and draws about 310mA, more than double on both counts.

More channels does not mean more wiring. It does mean more grams at the front of your chassis.

What 8 channels already solves

If your event is a straight track with turns and no branching path, the ARC8's weighted-average read across its curved 8-sensor arc gives your control loop everything it needs: a continuous position of the line relative to center, updated fast enough to correct before the next turn.

A single, unbroken path never asks the sensor to tell a junction from a curve, because there isn't one to tell apart.

If your track has one path and no branches, the ARC8 already gives your control loop everything it needs.

Where the extra channels start earning their keep

A junction looks different from a curve only if your sensor is wide enough, and dense enough, to see both edges of the track lose contact while the center stays clear. That's a real two-dimensional read, and it's what the ARC16's wider curved array and doubled channel count are built for.

The ARC16's case logic can tell a T-junction from a plus-shaped intersection, catch a circular loop by watching the outer sensors go active together, and recover from a track that inverts from white-on-black to black-on-white mid-run. None of that is guesswork. It comes from having enough discrete points across a wide enough arc to see the shape of the track, not just its center.

The ARC16 earns its extra channels the moment your event has more than one path to choose between.

The cost you pay for channels you don't use

Weight at the sensor mount matters more than the same weight anywhere else on the bot. It sits ahead of the wheelbase, so it adds to the moment of inertia your steering has to fight every time you correct into a corner. An unused 5 extra grams up front works against every turn-in, not just sitting there neutral.

Current matters too. At 150mA, the ARC8 runs comfortably off an Arduino Nano's own 5V pin, no extra hardware needed. At 310mA, the ARC16 sits past the point where Techgeeks' own build guides call for a dedicated 5V BEC instead, since that's close to where the Nano's onboard regulator starts to strain. That's one more component and one more soldered connection you didn't need with the ARC8.

Pick by your track, not the bigger number

Straight track, standard turns, no junctions on the event card: the ARC8 covers it, and costs you less weight and less power budget doing it.

Junctions, a maze round, circular loops, or a track that inverts partway through: the ARC16 is built for exactly that read, and the extra channels stop being dead weight the moment your logic needs to tell paths apart.

Building your first bot and the event format isn't locked yet: start with the ARC8. It drops straight into a standard build with no extra power planning, and you can move to the ARC16 later once a specific competition actually requires junction logic.

Conclusion

Sixteen channels isn't automatically better than eight. It's better at one specific job: telling a branching track apart from a single line. Everything else, it costs you in grams and milliamps whether or not that job ever comes up on your track.

So before you order the bigger array: does your event actually branch, or does it just turn?

Straight track this weekend, the ARC8 already covers it. Junctions on the card, the ARC16 is built for exactly that read.