Event game

September 2024

A company asked me to develop a small game for a business fair. Participants need to place 4 objects in the right place, after which a small scale windmill starts turning.

Adding detection to the table

To detect each object, an RFID tag is incorporated into each object. The table has a reader below each valid position. The readers themselves are modified to increase the detection range. In standard configuration these modules feature up to 2cm readout. By winding larger coils with fewer windings the current and thus range can be increased. The new inductance is calculated using a signal generator and a scope. This inductance allows us to find the correct capacitor values to maintain the correct readout frequency. Each module sends its data over UART. Since the used Arduino has only a single UART port, a 4 channel UART buffer is used. This buffer can be read over SPI. If all modules are powered at the same time they cause interference to each other. Thats why a later version used a loop that selects then one by one. To speed this process up the CRC of all tags are used. A single valid readout advances to the next reader. If no readout is detected within 1s, the loop advances as well.

Control electronics and housing

This table is powered over USB. A long cable extends to a power adapter. Damage has occurred to the PCB because of people tripping over this wire. To prevent this in the feature an extra housing is used for the PCB and the cable is looped and screwed into the table. This housing also prevents unwanted access.