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RAVEN-01

Raven-01

A low power sensor chip that detects sewer blockages days before they overflow.

DESIGNED AND VERIFIED IN SIMULATIONFPGA IMPLEMENTATION CHECKS PASSEDHARDWARE TESTING NEXT

1
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Overflows are found too late.

A blockage in a sewer grows over days. Today it is usually found when sewage comes up through a manhole or into a yard, and by then the cleanup, the health risk and the damage have already happened. A warning while the blockage is still forming gives a team time to clear it first.

Like a smoke alarm for a manhole.

Raven-01 learns what normal looks like in one manhole and stays quiet until something changes.

Why the warning has to come days early.

Once the outlet is fully blocked, a manhole fills from the alarm level to the rim in roughly 13 to 52 minutes per metre of space left, at an inflow of 1 litre per second, for chambers 1 to 2 metres across. No repair crew can arrive in minutes. The warning has to come while the blockage is still partial.

Calculated in the Raven-01 technical brief from conservation of mass.

ILLUSTRATION2

In simulation, Raven-01 raises a warning days before the overflow.1

How it works

ILLUSTRATION2

  1. A measurement scheduler with power control switches the sensors on for each measurement and off again.
  2. The echo ranger times the echo of an ultrasonic pulse.
  3. The temperature sensor interface reads the air temperature.
  4. The distance engine turns the echo time into a distance, corrected for temperature.
  5. The event detection engine, Naple's proprietary block, compares each level against what is normal for that manhole.
  6. A configuration interface holds the settings an operator can tune in the field.
  7. The serial link (UART) sends events and health reports out in checksummed messages.
Raven-01's main blocks and how data moves between them. A simplified illustration, not the physical layout.
  1. /01

    Wake

    A scheduler switches the sensor on for each measurement, about once a minute.

  2. /02

    Measure

    An ultrasonic pulse goes down to the water and the chip times its echo.

  3. /03

    Correct

    The speed of sound changes with air temperature, about 0.17% per °C, so the chip corrects every reading for temperature.

  4. /04

    Compare

    The chip learns what normal looks like at that manhole and compares each new level against it.

  5. /05

    Report

    It speaks only when something changes, plus a regular health report that shows it is alive.

  6. /06

    Sleep

    The sensor is switched off until the next measurement.

What has been proven, and how1

Raven-01

TYPE
Digital sensor hub chip
JOB
Early warning of sewer blockages
CLOCK
Single clock domain, 27 MHz reference
DISTANCE ACCURACY
±0.51 mm distance arithmetic, −20 to 70 °C (checked exhaustively in simulation)
SENSOR POWER
Sensor powered about 0.2% of the time
OUTPUTS
4 event types plus a health report, over a checksummed serial link
VERIFICATION
Byte identical to an independent reference model in two simulators
FPGA
Placed and routed on a Gowin GW1NR-9, timing met at 27 MHz, 40% of the device used
HARDWARE
Not yet run on a board
SILICON
Not manufactured
Read the technical brief (PDF)

ILLUSTRATION2

An illustration of two columns of output, one from the Raven-01 design and one from an independent reference model, matching byte for byte across several test scenarios.

The values shown are examples.

Where it stands

  1. /01

    Designed

    Done

  2. /02

    Verified in simulation

    Done

  3. /03

    Implementation checks for FPGA hardware

    Done

  4. /04

    Tested on FPGA hardware

    Next

  5. /05

    Field pilot

    Planned

  6. /06

    First silicon

    Planned

Designed for a real place

Raven-01 was designed for Mableroot, a school team working on sewage overflows in Illovo, KwaZulu Natal. Mableroot is its first case study.

Looking for pilot sites

We are looking for operators of pump stations, tanks and sewer networks who want to pilot Raven-01. Pilot hardware is agreed and funded with each pilot partner. If that is you, talk to us.

Talk to an engineer

Have a problem a chip should solve?

Tell us what is failing and where. An engineer will reply within two working days.

Talk to an engineerRead our research

Opens an email to hello@napletech.online.

DISCLOSURES

  1. All Raven-01 results on this site come from simulation and implementation checks. Raven-01 has not yet been tested on physical hardware or manufactured.
  2. This diagram is an illustration. It shows how the design behaves, not its physical layout or real measured data.