PoolGuard Latch
The pool gate you already have, now telling you when it didn’t close or something is against the fence
Measures every close of an existing self-closing, self-latching pool gate (home / bounced / stalled / propped) and warns from the close-time trend that the hinge springs are weakening. ClearZone camera pods on the fence posts watch the 900 mm strip outside the fence and send a photo when a chair, pot plant, esky or toy has been left there. Camera after-hours entry alerts remain an optional add-on for commercial pools.
- Who buys it
- Families with a backyard pool (US/AU); apartment, HOA and hotel pool managers; pool fence installers as the sales channel.
- Why it pays
- Replaces finding out by eye that the gate stands open; for commercial pools, a self-latch failure is a major health-code violation that can close the pool (est. days of lost amenity plus liability exposure), and the log replaces a paper walk-round.
- Target price
- Latch Kit $79; ClearZone pod $69; Fence Kit (Latch Kit + 2 ClearZone pods) $199; Smart Latch bundle (MagnaLatch S3 + kit) $169; commercial gate log $4/gate/month (targets). After-Hours camera add-on $2,190 + $49/month
- First-minute wow
- A photo on the phone: “Something is against the pool fence, east side”, with the kids’ ride-on car boxed in the strip. Three weeks later: “Gate A is closing 19% slower than when fitted. Adjust the hinge springs.”

What the research found
And how this design answers it
- Rev B: the camera kit was an attachment next to the barrier → the gate itself now reports every close, on any latch brand, with nothing opened or modified
- The gate is where barriers fail (21 of 32 investigated fenced pools: faulty gate or latch) → HOME / BOUNCED / STALLED / PROPPED result for every close, with a phone alert
- Climbable objects left by the fence are the other top inspection failure (Royal Life Saving WA; Auckland: 25% fail first inspection) → rev B1 ClearZone pods photograph the 900 mm strip 6 times a day and alert on a new object still there after 20 min
- Hinge springs weaken silently and gates stop latching from part-open → a weekly close-time trend warns at +15%
- MagnaLatch ALERT only beeps at the gate → phone alert, gate chirp and a log for inspectors and insurers
- Life-safety liability → no drowning, barrier or compliance claim; the fence and the listed latch stay the barrier
Use case
The ride-on car parked against the fence
ParentPool fence installer
- 01Trigger: after school a child leaves a ride-on car and a stacking chair against the outside of the pool fence
- 02Detection: the 4 pm ClearZone photo shows two new objects in the 900 mm strip; 20 minutes later they are still there
- 03Alert: the parent’s phone shows the photo with both objects boxed: “Something is against the pool fence, east side”
- 04Action: the parent moves them and taps “fixed”; the next photo is clear and the log shows the time it took
Outcome: The strip is cleared the same afternoon instead of at the next inspection, with a dated record
How it works
Architecture
- 01
Sense: LeafPod on the gate leaf (gyro swing angle, Hall gap to the PostTag magnet); ClearZone camera pods on fence posts; optional rev A cameras
- 02
Decide: on-device close classification and spring trend; on-device change map of the zone strip with a person/animal filter and a 20-minute still check
- 03
Send: home Wi-Fi, or the rev A PoolPost / IEMI Edge Hub at commercial pools, over outbound MQTT/TLS
- 04
Tell: phone alert with a photo or close result, gate chirp; weekly gate health and an inspection-ready log
Hardware
Real parts, buyable today
Bill of materials: about $43 per Latch Kit and about $39 per ClearZone pod at qty 1 (est.); After-Hours camera add-on about $805 per pool (est.).
| Block | Part | Why this part |
|---|---|---|
| LeafPod | Seeed XIAO ESP32C3 + Adafruit LSM6DSOX + TI DRV5055A4 linear Hall + 2 x AA lithium | Sleeps until the gate moves; about 2.4 years on 2 AA (est.); measures the gap to 0.08 mm |
| PostTag | N42 Ø12.7 x 6.35 mm magnet in a printed holder | Passive, on the latch post; no wiring |
| ClearZone pod | Seeed XIAO ESP32S3 Sense (OV2640) + Pololu S7V8F3 + 2 x AA lithium, on a 12° post wedge | Looks along the fence 25° down; a 0.45 m chair 10 m away is 48 pixels tall; about 700 days per battery set (est.) |
| Bundle latch | D&D MagnaLatch Series 3 Top Pull, unmodified | The listed latch stays the barrier |
| Add-on: Hub | IEMI Edge Hub: Raspberry Pi 5 8GB + AI HAT+ 26 TOPS (Hailo-8) + UPS | Reused platform, indoors on mains; nothing mains-powered at the pool |
| Add-on: Cameras | Reolink RLC-510A PoE + printed polariser hood | ONVIF, IP66, $40–59; polariser cuts surface glare |
| Add-on: PoolPost | Olimex ESP32-POE + TL-POE10R 12 V splitter + MAX98357A + horn + strobe | One PoE cable, low voltage, works with the internet down |
| Add-on: Gate | Wired N/C reed switch with 10 kΩ end-of-line resistor | Detects open, propped and cut wire |
| Add-on: Lifeguard band (phase 2) | Seeed XIAO nRF52840 + coin motor + 150 mAh LiPo | BLE buzz for supervised pilots only |
Mechanical
Printable CAD
16 parts, generated from code and checked as closed solids. Pick a part to inspect it, or download the STL files to print.
See the CAD parts render

Loading the CAD…
Real CAD · drag to rotate · scroll to zoomReal CAD · swipe sideways
Bought hardware fitted inside this part (checked in the CAD: nothing collides with the plastic)
- Polariser hoodpolariser-hood.stl · ASA
- Polariser ringpolariser-ring.stl · ASA
- PoolPost basepoolpost-base.stl · ASA
- PoolPost lidpoolpost-lid.stl · ASA
- Gate reed bracketgate-reed-bracket.stl · ASA
- Gate magnet bracketgate-magnet-bracket.stl · ASA
- Band pod bottomband-pod-bottom.stl · PETG
- Band pod topband-pod-top.stl · PETG
- Band strapband-strap.stl · TPU
- After-hours notice framenotice-frame.stl · ASA
- LeafPod baseleafpod-base.stl · ASA
- LeafPod lidleafpod-lid.stl · ASA
- PostTag magnet holderpost-tag.stl · ASA
- ClearZone casezone-case.stl · ASA
- ClearZone lidzone-lid.stl · ASA
- ClearZone post wedgezone-wedge.stl · ASA
Open risks we are working on
- D&D Technologies already sells the MagnaLatch ALERT and could add Wi-Fi
- Generic cameras (Ring, Arlo, Eufy) could add a “still object in zone” feature in software
- ClearZone accuracy with shadows, wind-blown plants and dew on the window is untested (T-Z1, T-Z2)
- A boundary-fence camera must not look into the neighbour’s yard; the strip mask needs checking for privacy
- Whether “latched” (not just “home”) can be sensed from outside the latch is untested (T-B3)
- Weak Wi-Fi at the fence line in many backyards
- Buyers may treat a gate or zone monitor as a barrier, compliance check or drowning-prevention device despite the wording
- Add-on: Buyers or plaintiffs may treat an entry alert as drowning prevention despite the wording
Design stage only: nothing on this page is for sale. Specifications and prices are targets.