Module Features: Supplement; Important Notes - DFRobot SEN0521 User Manual

When installing at an oblique angle downwards or parallel forwards, one must pay
attention to the direct detection of "air conditioners", "curtains", "fans", or "plants",
as their swinging frequencies may fall within the respiration frequency range, which
could result in false alarms from the module.
At the same time, it is necessary to be aware of multipath reflections that occur
when the beam is irradiated onto the ground, walls, or doors, which indirectly detect the
above-mentioned interferences in a manner similar to mirror reflections. Appropriate
parameter configurations for sensitivity and distance filtering can reduce some of the
interference.
2.

Module Features: Supplement

1. Within 5 seconds of initialization, the system will not detect any targets.
After the module is powered on or restarts, a self-calibration and initialization
process will take place for 5 seconds, during which no target detection will occur.
2. After the transition from manned to unmanned mode, there is a default protection time
of 1 second (blocking time).
When the module detects a change from manned to unmanned state, it triggers a self-
protection mode that lasts for 1 second by default. During this period, the detection
sensitivity is automatically adjusted to a lower level with a relatively high trigger
threshold. The purpose of this mechanism is to prevent the interference from high-
power actuators controlled through coordinated operations, which otherwise may
disrupt the module's system during the transition of states.
3. Subtle breathing movements or finger movements may sustain the presence of a person,
but there is a possibility that they may not trigger the module.
When the module's output is set to unmanned state due to micro-movements, larger
movements are required to trigger the module compared to pure subtle breathing
movements. On the other hand, when the module's output is set to manned state, even
very slight breathing movements can sustain the status of detecting a person's
presence.
3.

Important Notes:

1. Suitable installation location.
(1) Please note that the module should not be directly exposed to "air conditioners",
"curtains", "fans" or "plants" as the oscillation frequency of these objects may
fall within the breathing rate range, which may cause the module to malfunction.
(2) At the same time, attention should be paid to the potential multiple reflections
of the module's beam on the ground, walls or doors that may indirectly detect the
aforementioned interference as mirror reflections.
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