In this post we learn how to make an LED cricket stump for helping umpires declare a foolproof OUT, NOT-OUT decisions.

The Circuit Concept

You might be seeing these amazing cricket stumps in the ongoing 2015 ICC world cup cricket matches, which can be seen dazzle or light up brightly as soon the ball hits any one of the stumps.

It's invented by an Australian person named Bronte EcKermann and created by South Australian manufacturer Zing International.

It is said that the cost of these stumps may be as high as US$ 40,000 for each set, gosh!. The circuit of these LED stumps is assumed to be consisting of all sorts of complex designs using microcontrollers.

In this article we'll learn how each of these circuits can be built using ordinary components at less than $5 and yet be as effective as the original LED stump specs.

LED Bails Circuit

The first diagram below shows a circuit which may be employed inside the bails, the idea may be understood as follows:

The IC1 which is an IC 555 is configured as a monostable wherein R3 and C2 along with R4 decides the ON time of the LEDs.

An NPN  transistor T1 can be seen attached with pin2 trigger input of the IC, whose base is rigged with a couple of reed switches in series.

The idea is simple: The entire circuit is required to be fixed inside each of the bails with the reed switches enclosed inside the end tubes of the bails. Furthermore, a permanent magnet needs to be fixed at the upper ends of the stumps so that the reed switches remain closed for so long as these are held over the stumps.

The figure above shows how the magnets inside the stumps needs to be embedded and positioned for the bails to respond to these.

As long as the bails are held over the stumps, the reed switches stay closed ensuring a switched OFF T1. However the moment the bail is completely dislodged from the slots, allows the reed switches to open and switch ON T1 which in turn triggers the monostable illuminating the LEDs for a time period as determined by R3/R4/C2. The LEDs remain shut off until these are yet again positioned over the stumps for a repetition.

That takes care of the bail circuitry, pretty simple.... isn't that?

In the above diagram we can also see LDRs being positioned right at the top of the stumps just under small apertures that my be drilled on top surfaces of the stumps.

These LDRs become exposed to the ambient external light the moment the bails are dislodged from the slots. since these LDrs are supposed to be integrated with sets of identical monostables inside the stumps, the operation becomes responsible for illuminating the LEDs attached on the stumps, thus the entire system consisting of the stumps and the bails become synchronized providing a foolproof sequence of the proceedings.

LED Stump Circuit

The following circuit shows how the circuit inside the stumps needs to be configured for implementing the LED stump circuit operations.

In the diagram we are able to witness the integration methods of the LDRs with a 555 IC based monostable.

As long as the bails are held over the stumps, the ambient light stay blocked from the LDRs which keeps T1 switched OFF. but the moment the bails are thrown of the stumps, the LDRs become exposed to the ambient light enabling T1 to receive a biasing voltage which in turn triggers the monostable so that the LEDs are illuminated for the set period of time fixed by the relevant components.

The LEDs shut of after the set time has elapsed until the bails are restored over the stumps for yet another cycle.

Designed by: Swagatam.

Parts List for the above explained LED cricket stump circuit

R1 = 220K
R2, R4, R5 = 10k
R6, R7 = 220 ohms
R3 = 1M preset
C1 = 0.22uF
C2 = 100uF/16V
C3 = 0.01uF
T1 = BC547
IC1 = NE555

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