Trackmate cable length record?

[Toby Warg]

I have run timing systems with over 4000 ft of wire (Trackmate and Chronocone). Both worked fine.

Ski race systems run with wire over 3 miles long.

I don't think we are coming close to the limits, as long as the timer is imune to the noise and the additional capacitance loading of very long cables.....

Good to hear.

[Pat Chewning]

In both systems, the active timing pin is pulled to +5V by a pullup resistor. No current is flowing thru the wires or the switch until the racer hits the switch.

When the racer hits the switch, the current flows from the active pin to ground (the other wire in the system). This pulls the voltage to 0V (through the pullup resistor), and the wires, indicating a START or FINISH event.

The amount of time this takes is (negligibly) affected by the cable length. It will be proportional to the incremtal resistance of the cable (not the resistance of the pull-up resistor), and the incremental capacitance of the cable.

This is usually on the order of 1.0 vs 0.9 times the speed of light over the cable distance.

This can be ignored.

[Sj Kalliokoski]

Question is mainly how system checks switch, is it constant flow of current or does it look just for voltage, if first one then cable can be long. In both cases cable cam be long but there is slight time shift compared to real times related later case but even then times can be compared to each other.

[Pat Chewning]

I have run timing systems with over 4000 ft of wire (Trackmate and Chronocone). Both worked fine.

Ski race systems run with wire over 3 miles long.

I don't think we are coming close to the limits, as long as the timer is imune to the noise and the additional capacitance loading of very long cables.....

[Toby Warg]

we are talking about electrical impulses here.
you should ask any electrician to get detailed info,toby

Of course, but theory and practice are not always best friends.

[Donald Campbell]

we are talking about electrical impulses here.
you should ask any electrician to get detailed info,toby

[Toby Warg]

I set up my system with 1320 meters to one switch and about 25 meters to the other one. It worked without a problem until the rain came and one of the tapeswitches shortcut.

Is this the longest cable anybody tried so far?

I am interested in knowing about the limit of the system, since we use it for downhill too.