FieldSide
One sideline station per practice field: heat number, lightning clock, sprint timing and referee flag buzz
Does the jobs of FieldFlag (with HeatFlag's sensing head), OffsideFlag and SplitPole with one brain: a fence-post station works out the heat (WBGT) band and alerts coaches, hears lightning and runs the 30-minute clock, checks athletes in with a tap, lights big sideline digits, times sprints from the poles and relays the assistant referees' flags to the referee's wrist.
- Who buys it
- High-school athletic director or head athletic trainer (Texas, Georgia, Florida first), buying for the practice field that football, soccer and track share.
- Why it pays
- $1,690 + $299/yr for one field kit instead of $2,394 + $299/yr for our FieldFlag station with StrikeClock, RollCall and display ($1,496), an OffsideFlag Set ($249) and a SplitPole Squad Kit ($649); one ESP32-S3 replaces the nRF9151 board, the Pico 2 display controller, the StrikeClock chip and the lead-pole page (est.).
- Target price
- $1,690 field kit (station, display, flag Set, 4 sprint poles, 100 wristbands) + $299/yr; station + display alone $999 (target)
- First-minute wow
- Thunder 9 km away: the digits flip to a 30:00 countdown, every coach's phone buzzes and the referee's wrist band buzzes STOP, all from the same post that was showing sprint splits a minute earlier.
What the research found
And how this design answers it
- Four chips (FieldFlag nRF9151, display Pico 2, StrikeClock XIAO RP2040, SplitPole lead pole) → one LilyGO T-SIM7080G-S3 (ESP32-S3 + LTE-M) in the station
- StrikeClock pod on a light pole and RollCall tap pod → the lightning chip and the tap reader live inside the station box
- The sideline digits now show the heat number, the lightning countdown or the last sprint split
- The station is the ESP-NOW hub: SplitPole's clock sync and phone page, and a lightning or heat STOP buzz on the referee's band
- One FieldSide app holds heat logs, lightning stops, acclimatization taps, sprint results and match-day flag logs
Use case
An August Tuesday on a Texas practice field
Athletic trainerFootball and track coachesAthletesReferee crew (Saturday)
- 01Trigger: 15 minutes before practice the station posts the WBGT band; athletes tap in at the door for their acclimatization day
- 02Detection: the band goes up from Yellow to Orange at 4:30 pm; coaches get the new rest-break limits
- 03Count: track coaches run 30 m sprints through four poles; splits show on the digits and the coach's phone
- 04Action: at 5:10 pm a strike 9 km away flips the digits to a 30:00 countdown; on Saturday the same strike buzzes the referee's wrist
Outcome: One post does the heat log, lightning clock, check-in, sprint timing and the referee buzz; $704 less than our three products bought separately (est.)
How it works
Architecture
- 01
Sense: SHT45 shade air, PT1000 black globe, ultrasonic wind, AS3935 lightning, PN532 tap spot
- 02
Decide: ESP32-S3 solves WBGT and the rule band, runs the 30-minute clock, segments sprint crossings and relays flags
- 03
Send: LTE-M (SIM7080G) to the cloud; ESP-NOW to the flags, band and poles; its own Wi-Fi hotspot at the lane
- 04
Tell: 200 mm RGB digits on the fence, FieldSide app with push and SMS, referee band buzz, PDF/CSV logs for the AD
Hardware
Real parts, buyable today
Bill of materials: about $1,290 per field kit at qty 1 (station ~$546, display ~$108, flag Set ~$78, 4 poles ~$560) (est.).
| Block | Part | Why this part |
|---|---|---|
| Brain | LilyGO T-SIM7080G-S3: ESP32-S3 + SIMCom SIM7080G LTE-M/NB-IoT + GNSS | One chip with the ESP-NOW radio the flags and poles already use, plus a cell modem for the logs |
| Heat | Sensirion SHT45 in a printed shield, PT1000 in a 150 mm black globe via MAX31865, Renke ultrasonic wind | FieldFlag's WBGT head, unchanged |
| Lightning | SparkFun AS3935 board inside the station | StrikeClock's chip, now on the brain's own bus |
| Display | 4 x 200 mm digits lit by WS2815 strip | Driven straight from the brain |
| Flags and poles | OffsideFlag grips + band and SplitPole heads (XIAO ESP32-C3 each) | They must be in hands and on the lane; they now report to one hub |
| Power | 30 W solar, BQ24650 charger, 12.8 V 12 Ah LiFePO4 | About 2.8 days with the display lit 4 h a day (est.) |
Mechanical
Printable CAD
10 parts, generated from code and checked as closed solids. Pick a part to inspect it, or download the STL files to print.
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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)
- Station case with U-bolt earsstation-case.stl · ASA
- Station door with TAP spotstation-lid.stl · ASA
- Sensor armsensor-arm.stl · ASA
- Radiation shieldshield.stl · ASA
- Sideline digit moduledigit-module.stl · ASA
- Referee flag gripflag-grip.stl · ASA
- Referee band caseband-case.stl · ASA
- Referee band lidband-lid.stl · ASA
- Sprint pole headpole-head.stl · ASA
- Sprint pole head lidpole-lid.stl · ASA
Open risks we are working on
- WBGT accuracy is unproven: FieldFlag's MAE ≤ 0.5 °C gate against a reference still applies
- AS3935 inside a box next to an LTE modem and Wi-Fi may hear switching noise as disturbers; firmware masking and a bench test are needed
- ESP-NOW range from one fence post to the far touchline (about 70 m) and to poles across the field is untested
- Referees buy their own flags and leagues must allow electronic flags; the school is not their buyer
- Measurement and alert only: it does not decide practice is safe or that play may resume, and is not UIL or NFHS approved
Design stage only: nothing on this page is for sale. Specifications and prices are targets.