As the robot arm uses a vacuum sucker to move tokens, it can happen, that the robot misses a token or looses it in transit. The original model isn't able to detect such situations.
In order to add this feature, I used a standard cylinder, a standard switch and a spring feather to construct something of detecting the presence of a vacuum.
The cylinder is simply added to the connection to the sucker via t-junction and as soon as there's under-pressure, is pulls back the cylinder, which presses the switch. As soon as the vacuum is lost, the spring feather pushes the cylinder back up and the switch is no longer pressed.
With this cheap little trick I can reliably detect if the token is still "hanging on" to the robot arm.
For automating this model I'm using a Beckhoff C6920-0030 PLC.
As this device has no built-in IOs I also purchased:
EK1100EtherCat Bus-CouplerEL180916-channel digital inputEL280916-channel digital output
The IO modules are directly connected to the bus-coupler and the bus-coupler is connected to the PLC via direct Ethernet cable.
For the communication between PLC and bus-coupler it's using the EtherCat protocol.
Here's how I connected all inputs and outputs to the PLC
The following values are positions in the Fischertechnik factory.
| Axis | vert | hor | rot |
|---|---|---|---|
| Register | R4096 | R4100 | R4104 |
| Blue Bay | 760 | 420 | 285 |
| Red Bay | 760 | 270 | 355 |
| Green Bay | 760 | 240 | 438 |
| Oven Intake | 420 | 840 | 880 |
| Hig-Bay Ingest | 40 | 20 | 1324 |
| Hig-Bay Output | 120 | 220 | 1324 |