This is to show my track and to explain a bit how the bits and pieces are connected. Maybe it is also a little bit of help for others like me, who are not really experts in electronics.
First - my track is the same as my nickname. Both are related to the country and town I'm living in. This town is Griesheim - near Frankfurt - which is a little bit famous for the "production" of onions. So the direct meaning of Zwiebelring in German is "onion ring". But ring has also a second meaning in German - it is quite often used also as synonym of circuit or track. Here we go - it's a pun ...
So the Zwiebelring is my four lane home track. Lap counting is done by PCLC (of course). The sensor for lap detection is a DS300. There is an external set of starting lights powered by 12V. Using an external button the race can be paused and the power is switched off. In this case also all five lights blink. External button, power and lights had been connected by parallel port before. This has been changed by squeezing in an Arduino recently. This means the output of the Arduino is put on a parallel connector and the rest afterwards still can be used as it was before with the parallel interface. The parallel cable connects my Arduino box with a relay card, which on one side actually switches on and off the lights and on the other side is connected by a single cable to another relay box containing a single relay for power control of all four lanes.
int LIGHT5 = 2; int LIGHT4 = 3; int LIGHT3 = 4; int LIGHT2 = 5; int LIGHT1 = 6;
int PWR = 7;
int NEXT = 12; int NEXTstatus = 0; int NEXTflag = 0; int LED = 13; unsigned long T1; unsigned long NEXTinhibit = 1000; // minimum time between first button pressed and next