PCLC, Phidget 8/8/8 and Light Bridge

I notice that the topics here either address the 8/8/8 with slot-mounted IR sensors, but don't seem to talk about using the 8/8/8 with a light bridge. I will be using PCLC with Windows XP, a Phidget 8/8/8 and a light bridge above the track. I'm not sure I need to worry about the wiring schematic that Slotmanege has posted, as that seems to apply only to the slot-mounted IR sensors needing a longer "pulse" to trigger the Phidget than the guide passing by them triggers. Since I'm using a light bridge, the sensors are blocked for a longer time (the length of a car), and the resulting pulse is longer. Is the timing circuit still necessary? Can I use the pit stop/refueling options with this kind of a setup?

Perhaps the guys at MainLine Hobbies can answer, as they seem to have investigated these issues....

Thanks in advance,
Stan

Hi Stan,

When using a lightbridge with Phidget 8/8/8 you do not have to use the extra timing circuit anymore. Probably the IR lightbridge sensors are blocked long enough by the passing slotcars.
I even think you can use the Schema to connect detector to Phidget 0/16/16:



Only thing you have to take care of is : make sure you offer the correct voltages to the Phidget's digital input (blocked sensor = 0 Volts).

Good luck !

Regards,
Danny

Danny:

Thanks for the response. It's what I thought...the light bridge should work without the timing circuit. I have yet to get everything wired up, but I'll post my experience with the light bridge as soon as I get any information.

Stan

Danny:

I finally have my Phidget wired to the track, although it's not powered by anything other than the USB circuit. Is it necessary to have the circuit powered, as depicted in your circuit diagram (i.e., 5 volt power to the Phidget and detectors)?

I am experiencing false lap counts and the Phidget doesn't control track power, though I THINK I have the setup configured properly. Is this a result of too little power to the Phidget? Any advice you could give me would be welcome.

stan

Hi Stan,

The Phidget 8/8/8 is only powered via the USB.



As you can see in the diagram 1 below (previous post) the GND is connected between the Phidget's Digital Inputs and the powersupply for the sensors. This is mandatory because the digital inputs always should have a reference. The signal that the sensors produce should always be measured against the same GND.

Also make sure there is a +5V on the digital input when sensor is not blocked. The Phidget 8/8/8 only reacts on a voltage drop from +5V towards 0V (GND). So when the sensor is blocked the digital input should be 0V. Measure these values with a multimeter just to be sure your sensor works fine.

And offcourse the sensors should have +5V power.

We also encountered many false lap counts when we just started with wiring up our hardware. The problem here were dangling/floating inputs AND we had a lot of troubles due to electro magnetic influences (EMC). Solution is to use shielded cables between sensors and phidget AND make sure the signals on your inputs are +5V (unblocked sensor) or 0V (blocked sensor)... strange voltages in between can cause Phidget to react.

Also check if you have installed the correct Phidget.msi and configured the inputs. Also check this thread for more info.


Controlling the trackpower via the Phidget output: The phidget outputs have a limited current so it is better to use a transistor (BC547B) to control the relais. It is not possible to hook-up the relais directly on the Phidget digital outputs.

Hopefully now it works !
If you have questions, do ask !

Regards,
Danny
http://www.slotmanege.nl