PIR Switch for Under-Cabinet LED Strips: Compatibility and Placement
Match a PIR switch to 12V or 24V LED strips, check load and timer behavior, and place the sensor where it detects countertop work.
For a conventional single-white 12 V or 24 V LED strip, choose an inline DC PIR switch rated for the strip’s voltage and full load current. It normally connects after the constant-voltage power supply, before the strip. Then check the two specifications that matter most at a kitchen counter: whether movement restarts the shutoff timer, and whether the sensor works in daylight.
A PIR detects changes in infrared radiation, not simply the presence of someone standing at the counter. A short timer can therefore switch off task lighting while you are still using it but moving very little. Panasonic explains the detection principle.
Check the switch before buying
“Motion sensor,” “IR switch” and “touchless switch” do not necessarily describe the same behavior. A hand-wave switch provides deliberate control; a PIR provides automatic motion-triggered control. Armacost’s touchless dimmer, for example, uses infrared emitters and sensors to detect nearby objects, rather than the passive detection used by its PIR switch.
| Specification | What to verify for under-cabinet lighting |
|---|---|
| Supply voltage | Explicit support for your strip’s 12 V DC or 24 V DC supply—not just “low voltage.” |
| Switched load | Maximum output current and wattage at your operating voltage, covering every strip section switched together. |
| Strip type | Documented compatibility with single-white, tunable-white or RGB lighting, as applicable. |
| Off-delay | Fixed or adjustable duration, and whether each detected movement restarts it. |
| Daylight behavior | Whether an ambient-light threshold prevents switching on in a bright kitchen; check for adjustment or disable options. |
| Detection and mounting | Range, viewing angle, permitted orientation, sensor-head dimensions and cable reach. |
| Manual control | A documented permanent-on mode or override if you need uninterrupted task lighting. |
| Location rating | Suitability for the actual exposure; a dry-rated sensor belongs away from splashes and steam. |
A concrete example: Armacost’s model 532520 supports 12–24 V DC, with a 4 A limit: 48 W at 12 V or 96 W at 24 V. It is dry-rated and intended only for single-color white lighting, not CCT or RGB+W. The lights stay on for 30 seconds after the last detected movement. As of November 2026, its product page also says activation occurs in the dark, but gives no ambient-light threshold or adjustment instructions. Confirm daylight operation with the supplier before choosing it for daytime task lighting. These are model-specific limits, not universal PIR specifications.
For comparison, Hera lists adjustable run-on times of 10 seconds to 3 minutes for its PIR 1S/2S variants. Its range includes both mains-side and 24 V DC models, so the family name alone is insufficient to identify the right switch. Hera PIR range details
Calculate the load through the PIR
Use the installed strip length and its rated watts per metre:
Total watts = installed metres × watts per metre Current in amperes = total watts ÷ supply voltage
For example, 4 m of strip rated at 12 W/m totals 48 W. That draws 4 A at 12 V, or 2 A for an equivalent 48 W installation using 24 V strips. The 12 V example reaches the Armacost switch’s stated maximum; choose a higher-rated compatible switch if you want capacity beyond that load. A larger power supply does not increase the PIR’s switching capacity.
Include all branches fed through the sensor, not just the longest section. For broader circuit sizing, see amps-to-watts conversion.
Wire an inline DC sensor on the low-voltage side
For a compatible two-wire white strip, the arrangement is:
Power supply DC output → PIR receiver “DC IN” → receiver “LED OUT” → LED strip
Disconnect power before making connections. Follow the receiver’s terminal labels, maintain positive-to-positive and negative-to-negative polarity, and connect the separate sensor head to its designated receiver connector. Secure cables where cabinet doors, drawers and mounting screws cannot damage them.
This is the arrangement specified in Armacost’s installation instructions. That model requires a standard electronic constant-voltage DC supply and a low-voltage Class 2 circuit installed to applicable national and local codes. It excludes magnetic supplies and 12 V AC-output supplies, and must not be connected to 120 V AC.
Do not assume a PIR can be added anywhere in an existing dimming circuit. Armacost’s product page excludes AC dimmers for this model. If keeping a PWM dimmer or color controller, obtain a supported wiring arrangement for the exact components rather than improvising their order. See matching a 12 V dimmer to the LED circuit.
Keep this retrofit to accessible low-voltage connections. Fixed mains wiring or changes to a hardwired driver’s supply belong with a qualified electrician.
Place the sensor for countertop movement
Start with a temporary position beneath the cabinet where the lens has an unobstructed view of your normal working position. Do not hide it behind the cabinet’s front lip or inside the LED channel. Prefer a view that lets your movement cross the detection area rather than only approach the sensor head-on.
Panasonic’s infrared-sensor installation guidance explains that sideways movement is easier to detect than direct approach, obstacles block detection, and substantial temperature fluctuations can cause incorrect detections. Apply those principles while following your chosen cabinet sensor’s own mounting diagram; another sensor’s quoted range is not a guarantee at countertop height.
Aim to cover the working position without unnecessarily covering the kitchen walkway. Keep the sensor within its specified environmental limits, away from sink splashes, hob heat and steam.
Before drilling or concealing wiring, test the complete setup:
- Approach from both ends of the counter and work at each lit section.
- Continue ordinary food-preparation movements longer than one timer interval to check retriggering.
- Pause with little movement and measure when the light switches off.
- Repeat with daylight and the main kitchen lights on to check ambient-light inhibition.
- Walk past without using the counter to check unwanted activation.
If normal countertop work fails to retrigger the sensor, reposition it or choose a longer-delay model. If you need light to remain on through stillness, select documented permanent-on control or a deliberate hand-wave/manual switch instead of relying on PIR detection alone.