sACN Multiple Sources: Priority, HTP Merge and Failover Troubleshooting

LikeLight Tom · Operations · Technical reviewer: pending confirmation

Summary

When a facade suddenly follows the architectural controller instead of the show console—or remains at an unexpected level after one controller is closed—the network may have multiple sACN sources for the same universe. The visible result depends on source priority, equal-priority merge behavior, receiver source limits and source-loss handling.

ESTA lists ANSI E1.31-2025 as the current sACN standard [S1]. ETC documents priority values from 0 to 200, with 100 as the default in its explanation, and shows that a higher-priority source can control a whole universe while equal highest priorities may be merged by HTP [S2]. Do not assume every receiver supports the same number of sources or optional priority behavior.

1. Identify every control source

Possible source	Why it stays hidden	Evidence
architectural controller	runs continuously in a cabinet	CID, source name, universe list
show console	operator expects it to be primary	priority and output status
backup processor	may still transmit while “standby”	packet capture and redundancy state
gateway DMX input	converts local DMX into sACN	gateway port configuration
test/visualizer tool	forgotten after commissioning	workstation process and source CID

An IP address alone is not a durable source identity. Record CID, source name, universe, priority, sequence activity and the physical device responsible.

2. Priority first, then merge

For per-universe priority, the highest active priority source controls the universe. If several sources share the same highest priority, a receiver may use HTP or another documented algorithm. ETC provides a clear HTP example and warns that receiver source capacity varies [S2].

Worked four-slot example

Source	Priority	Slot 1	Slot 2	Slot 3	Slot 4
architecture	100	75	100	50	0
console	100	35	15	65	25
equal-priority HTP result	—	75	100	65	25
console changed to priority 150	150	35	15	65	25
higher-priority result	—	35	15	65	25

The higher-priority result is not HTP against the lower source; the selected higher-priority source supplies all shown slots in this teaching example. Values are illustrative, not project observations.

3. Why takeover can still fail

Symptom	Likely cause	First proof
console cannot take control	its priority is lower or receiver remaps input priority	compare packet and receiver settings
mixed levels from two systems	equal priority with HTP merge	inspect both source values
new emergency source ignored	receiver already reached source limit	receiver source table and manual
old look remains after source closes	source still transmits, termination missing or hold state	capture packets and gateway status
backup takes over slowly	source-loss/timeout and recovery logic	timed interruption test
only some addresses transfer	per-address priority or local arbitration	slot-level viewer and patch

MA Lighting documentation demonstrates that a receiver can expose its own merge and input-priority behavior [S4]. Verify the exact implementation rather than transferring another vendor’s settings.

4. Controlled diagnostic procedure

Back up controller, gateway and switch configurations.
List every source for the affected universe by CID, name, IP, priority and responsible owner.
Capture the same universe at the source and receiver side; confirm that “closed” systems truly stop transmitting.
Use a source-aware viewer to inspect the winning source and competitors per address where supported [S3].
Test one source alone, then add the second at lower, equal and higher approved priorities.
Record equal-priority merge results for intensity and non-intensity slots; do not assume HTP is suitable for every parameter.
Test the receiver’s documented maximum source count and the behavior when an additional source appears.
Perform planned stop, network loss, restart and return-of-primary tests with timestamps.
Confirm gateway DMX output and fixture behavior separately.
Freeze the priority matrix, owner, takeover procedure, rollback and acceptance log.

5. Product boundary

LIKELIGHT publishes L-W-10036-DMX as a 36 W, DC24 V, RGB, DMX512 wall washer [S5]. Its public page does not state sACN capability, source priority, merge algorithm, receiver limit or failover timing. These functions belong to the selected controller, node/gateway and system design unless the exact ordered fixture documentation says otherwise.

For review, provide the complete source inventory, universe/slot ownership matrix, gateway model, DMX patch and required emergency/architectural/show takeover logic.

6. When not to use equal-priority HTP

Do not use HTP as an undefined compromise between two systems that should have clear ownership.
Do not expect HTP to represent latest-position behavior for movement or mode parameters.
Do not raise priority to 200 merely to “make it win” without an operational release plan.
Do not leave test software transmitting after commissioning.
Do not approve redundancy without timed source-loss and return-of-primary tests.
Do not infer sACN behavior from a DMX512 fixture label.

FAQ

Does priority 150 merge with priority 100 by HTP?

Normally the higher active priority is selected first; confirm the receiver and current standard behavior.

Why does a zero value from the console override a higher level?

If the console has higher priority, its universe data may win even when an individual value is lower.

Can two equal-priority sources be safe?

Only when the merge rule, slot types and operational ownership are intentionally designed and tested.

Why is a third source ignored?

The receiver may have a concurrent-source limit or filtering rule. Check its table and documentation.

Is per-address priority universally supported?

No. Both source and receiver must support the relevant behavior; verify actual packets and device documentation.

What proves failover?

A timed test showing source loss, selected replacement, output behavior, alarms and return sequence—not a static diagram.

Sources checked

2026-09-16

LIKELIGHT L-W-10036-DMX wall washer example

Submit project requirements

A string that lights on the bench can still arrive with the wrong voltage, IC timing, color order or data direction. Release one representative branch only after the label, pinout, effects, loaded end voltage and replacement method agree.

The page lists two voltages and two power values without pairing them. Keep the load as a 1.44-2.16W range per point, then freeze the approved voltage-power version before calculating current, circuits and controller commissioning.