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TI Innovation Challenge·2015

Broken-rail detection with optical fibre

Laser pulses through a plastic fibre bonded to the rail: a break cuts the light, and a control station texts the train driver over GSM. Semi-finalist award, Texas Instruments Innovation Challenge India 2015 (top 86 of 1,209), featured in The Times of India.

Problem

India runs one of the world’s largest rail networks, and sabotaged or broken track is a real danger, especially in regions where tracks have been blown up. Track circuits detect breaks by electrical conductivity, but they can miss a break over tie plates or in salty conditions, can be knocked out by lightning, and are absent in dark territory. Patrols and pilot engines are slow and put people at risk.

What I did

With Rahul Choudhary, Aditya Vidolkar, Rohit Salem and Ashish Ghatge, mentored by Dr B. S. Umre at VNIT, I built an optical alternative for the Texas Instruments Innovation Challenge India 2015.

A laser, driven through a driver circuit designed with TI WEBENCH, sends a stream of light pulses into a plastic optical fibre bonded along the rail. At the far end an OPT101 photodiode with an LM741 amplifier feeds the ADC of a TI LaunchPad. If the rail breaks, the fibre breaks with it and the light drops; the detector crosses its threshold, tuned with a serial oscilloscope, and radios the control station over a CC2500 link. The control station, an MSP430F5529 LaunchPad with a GSM module, sends an SMS to the driver of the train scheduled on that track. Three LaunchPads ran the pulse generation, the detection and the control station, all programmed in Energia.

Result

The prototype (highlights in the video at the top) reliably detected a break in a 30 m fibre and sent the SMS alert, and won a semi-finalist award at the Texas Instruments Innovation Challenge in Mumbai: top 86 of 1,209 teams. The Times of India covered the project in May 2015 (“VNIT students find way to detect rail fractures in real time”). We did not finish localising where along the track the break was, which we left as future work.

system

scroll sideways on small screens

How the break is detectedTop: a laser sends pulses through an optical fibre bonded along an intact rail to a detector, which sees light. Bottom: the rail breaks, the fibre breaks with it, the detector sees no light and raises an alert.Intact railLaser650 nm pulsesDetectorlight ✓optical fibre bonded along the railBroken railLaser650 nm pulsesDetectorno light → alertrail break
SystemPulse generator: a TI LaunchPad drives a laser driver and laser diode into the fibre. Pulse detector at the far end: an OPT101 photodiode, an LM741 amplifier and a LaunchPad ADC, sending status over a CC2500 radio. Control station: a CC2500 radio, an MSP430F5529 LaunchPad and a GSM module that texts the train driver.Optical pulse generatorLaunchPadPWMLaserdriverLaserdiodeTI WEBENCH driver designfibre on railOptical pulse detectorOPT101photodiodeLM741amplifierLaunchPadADCCC2500RFControl stationCC2500RFMSP430F5529LaunchPadGSMmoduleSMSrail breakaheadtrain driverwireless statusGSM text
Where the fibre goesRail cross-section. The fibre is mounted on the vertical web directly under the head, avoiding fasteners at the base, maintenance-of-way equipment, markings on the centre of the web and drilled holes for rail joints.headwebfootfibre: web, just under the headclear of fasteners at the baseoff the centre-web markingsaway from drilled joint holesout of reach of maintenance equipment
diagramsHow a break is detected, the system the team built from TI parts, and where the fibre sits on the rail.Source: the team's 2015 report

footage

muted, looping

The problem: sabotaged and broken track, and why manual patrols are not enough.
The prototype: the rail model, laser driver, laser diode into the fibre, and pulses on the oscilloscope.
The alert: the control station picks up the break and the GSM module texts the driver's phone.

figures

click to enlarge

fig. 01Laser pulses arriving at the detector, seen on the oscilloscope.Team 1293 report
fig. 02Certificate from the TI Innovation Challenge India Design Contest 2015: the team was among the 86 semi-finalist teams from 1,209.TI University Program
fig. 03Detector output on the serial oscilloscope: the signal drops when the fibre is cut, crossing the alert threshold.Team 1293 report
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