Lap Timer Software and Laser triggered Photo Transistor Timing Gate

“Going around in circles is a lot more fun when you keep time!”

Test setup using a Carerra Slotcar Track

Originally I considered programming my own lap timer. I researched several Javascript options and stumbled more or less by accident into several slotcar forums and sites. I grew up with a Carrera 140 Servo Slotcar track and just recently acquired a Carerra Go track for some family fun. Turns out the slotcar boys are really into precise timing and “why re-invent the wheel” when a genius like Gregory Braun over at hoslotcarracing.com already build a great piece of software.

In a nutshell the setup uses a standard Photo transistor connected to a Gameport to USB adapter which is plugged into a Windows computer (the pic above is a Intel chipset Macbook Pro booted into XP). A laserpointer is mounted across the track. Every time the vehicle interrupts the laser beam the photo transistor acts like a joystick button is being pressed and the lap timer software interprets this as a lap being completed. Note: my setup here can only support one vehicle on the track. Mount your photo transistor into your track and build a bridge with light source from above for multi car setups. For slotcars you can get away with LED’s as lightsource, however due to the wider wheelbase of 1/10 scale R/C cars and the consequently bigger space between photo transistor and light source I recommend a laser pointer as light source.

Infrared Photo transistor triggered by Laser pointer

The banana jacks on the top are wired to joystick button 3 and 4, allowing for 2 additional photo transistors or any other switch to trigger the timing software. A USB to Gameport converter is housed inside the project enclosure.

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Components:

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Gameport to USB Adapter – available at Amazon $20

Infrared Phototransistor – available at Radioshack $1.95

Project Housing/Enclosure 6x4x2 – available at Radioshack $4.99

Banana Jack 4x – available at Radioshack $2.99

Flashlight Reflector

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Internal Wiring

Pin 1-14 are according to a PC Gameport.

The image below was created by HO Slotcar Racing.

Here is a great graphical Pin-out of a PC gameport

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Software

The Lap Timer Software will run on Windows XP and can time up to 4 vehicles at the same time. I have not tested the lap timer using Vista.

Download here.

Credits: Lap Timer Software is created by Gregory Braun at hoslotcarracing.com