Scoreboard

May 2019

A tennis club frequently organizes events where participants need to hit a certain target. They asked me to create a solution to their former way of keeping track of the score, which used cards being hung up and taken down. The solution consists of a box with speakers and amplifier showing the score at the front. The score is created by segments made up from red LED strips. The score gets increased by an amount determined by where the target is hit. A smoke machine can be connected to the scoreboard as well for extra show. This project is powered by a battery so it can be used at remote locations

Creating the housing

The housing is drawn first. The front will have slots for the LED strips. These slots are cut out using a router. The back panel allows access to the electronics and has connectors for the smoke machine and charging. The sides have a hole each for a large speaker. This speaker has a specific sound per type of increment. Inside the housing are the control electronics and a battery. The battery allows using the scoreboard on remote tennis courts.

Adding electronics

Once the housing is created the electronics are added. The scoreboard can count to a maximum of 999. So three segments are used, each consisting of 7 pieces of LED strip. Each of these digits and their segments are powered using a large segment driver. These consist of a 8 bit shift register and 8 MOSFETs. Multiple drivers can be chained to each other to control all 3 segments. When a latch pulse is given the bits in the registers are transferred to the holding register and the MOSFETs. The signalling comes from an Arduino Nano. To control the speakers a small amp is used. The sound comes from a DFRobot MP3 module, which can be controlled using UART.

Programming

Once all electronics are in place the Arduino can be programmed. The clock, latch and data signals are programmed, as well as when to play each sound. A WS2812B LED strip can also be attached

Later modifications

Initially, the scoreboard score increments were triggered using a piezo-electric element which's signal was amplified using an opamp setup. However, tennis balls would hit the target with such force that the element broke frequently. The element was later replaced by a 4 channel remote to solve this.