USB Gamepad Slotcartimer - Ir-lotsensor

This is the second variation of my slotcar timer interface. Where the gamepad was triggered by a "deadstrip" the first time I am now using an IR-slotsensor to trigger the gamepad.

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EDIT
The third and refined version can be found here:
https://www.instructables.com/id/cheap-USB-slotcar...

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• TCST 2103 ir-slotsensor

• Darlington transistor BD679 NPN

• 5 V/DC Reed relay

• 10kOhm and 100Ohm resistor

• z-diode 5V LED

• (optional but good for testing)

This will set you back some 4-6€, depending on where you source parts.

I am leaving cheap and going for a "perfect" solution.

Here is the circuit.
The LED is optional but you can test your circuit with it.

I am not sure at this point how accurate the hardware will detect the cars.
It will probably work good with 1:32 cars but have a hard time detecting 1:43 scale cars.
When I pull a toothpick through the ir sensor they are not always detected. 1:43 slotguide pins will probably not get detected.

The reed switch closes very fast and works rather good.

Ideas how the stretch the switching would really be appreciated.

I also bought an opti coupler, this it the next part I would love to test.

Of course the slotsensors would have to be installed in the slot.

I am just learning electronics for some days now so please excuse any stupidity I may display writing about this vast topic.