Background – Purpose of the Project
Our customer is developing an indoor entertainment venue with multiple activities. One of them is the smart mini golf game.
Eccel were asked to develop a “Smart” Golf Ball which would allow all elements of the mini golf game to be read electronically. This includes the hole which the player is on, the total number of shots taken and finally provide a score on the scoreboard at the end for each player.
In order to record this information, Eccel would also need to also implement RFID boards and antennas to sit underneath the golf course to track the Ball as it travelled around the course.
Challenges to address
The selection of a resin with the appropriate hardness was a key factor in the project. The ball couldn’t be too bouncy, it couldn’t bounce like a tennis ball. It also couldn’t be too hard, otherwise it would act like a stone. The color of the resin was also important. A partially transparent resin was needed so that the LED light was clearly visible. Additionally, we chose a resin that disperses light well, which gave the effect that the entire ball is glowing. All electronics are potted with polyurethane resin of appropriate hardness.
The main element of the project is the smart ball. Inside the ball there is a PCB with components and a Li-Ion battery that powers all the electronics. The board has an accelerometer, RGB LED, a dynamic RFID/NFC tag, a battery charging system and, above all, a microcontroller with Wi-Fi and Bluetooth support.
Furthermore, the ball’s firmware can be updated over Wi-Fi (OTA). This allows the customer to introduce some tweaks and upgrades in the functionality, without making new balls.
A special silicone mould was designed to produce balls, in which a real golf ball was imprinted. This enabled us to obtain a cast in the same shape as a golf ball with dimples. Many types of resin were used and tested to select the best one.
The ball is fully sealed, so a completely wireless battery charging system also had to be implemented. Charging stations for 8 balls using an RFID field have been designed to charge batteries inside the golf balls. We managed to obtain a battery charging current of approximately 30mA. Thanks to this, it is possible to fully charge the ball in approximately 6-7 hours.
The game system also includes RFID readers – Pepper C1 with external antennas.
Each reader additionally has an external RFID antenna with a cable. Such an antenna can be of various sizes and shapes (maximum approximately 20x20cm). The bonus point reader may have a larger antenna so that it can detect balls over a larger area. Readers in holes may have a smaller area, e.g. 25×25, to avoid false readings, e.g. when the ball is very close to the edge of the hole but has not yet fallen into it.
Pepper C1 EA UART: https://eccel.co.uk/product/pepper-wireless-c1-ea-uart/
RFID ANT 80×80-800: https://eccel.co.uk/product/rfid-ant1356-80×80-800/
The following devices were needed around the golf course:
- Authorization reader – used to activate the ball and assign it to the player
- Start game reader – used to activate the game mode by the ball
- Bonus point reader – if the ball passes through the RFID field generated by the bonus reader during the game, the player will receive a bonus point. This can be used to check whether a player has sent the ball through a “difficult route”. Another reader of the same type can be used to calculate penalty points.
- End hole reader – if the ball falls into the hole in which the RFID antenna of this reader is placed, it means that the player has completed the given hole
- End game reader – if the ball falls into the hole where the RFID antenna of this reader is placed, the game will end and the game results will be saved in the local hole server database
The Intel NUC – mini PC with Linux Ubuntu was also added to the board to act as a local hole server on each hole. This server receives information from RFID readers around the hole (over TCP connection) and stores them in the MySQL local database.
This is how the whole process works from Ball to Interface:
The Final Product
What the user sees
How it looks underneath
How the game works:
- The balls rest on the charger and charge their batteries.To start the game, take one ball in your hand and shake it to wake up the microcontroller from deep sleep mode.At this point, a blue LED illuminate to indicate that the ball is ready for authorization.The ball will remain in this state for 1 minute.If this time is exceeded, the LED will turn off and the ball will enter charging mode again.
- Then the player must place the ball on the authorization reader, launch the PC application, enter his name there and click the “Authorize” button.At this point, the reader will transmit the player’s name along with the unique ball ID to the database located on the server of the hole 1. The LED color will now change to purple, informing the player that authorization was successful.At this point there are 10 minutes to start the game.After this time, if nothing happens, the ball will return to charging mode.
- The player can now place the ball on the starting point on hole 1. If the start reader correctly recognizes the ball, the LED on the ball will turn green for 1 second and then turn off.This will inform the player that the microcontroller has gone into sleep mode and the game has started.
- Each time the player hits the ball, the LED will light up in the selected color and will remain on as long as the ball continues to move.After 3 seconds of inactivity (no movement), the LED will turn off and the microcontroller will go back to sleep mode.After each shot, the ball increases the hit number and sends this number as a Bluetooth GAP packet to Pepper C1 readers located on a given hole.Then, the readers, connected to a common Wi-Fi network with the server, transmit this information to the server, where the data is saved in the local MySQL database of each hole.
- When the player hits the ball into the hole, the end hole reader will send this information to a database located in the cloud.This way of playing allows players to play remotely.Even players from different parts of the world can compete with each other as long as they play the same holes.
Smart mini golf game in action
Please have a look at the video showing the wooden model of the golf game :