in my area there any way too many different types of cars to organize. was thinking to build a lap time system using garage door opener safety sensors. they could trigger a stop watch? that way people could race the clock instead of each other, then all sorts of cars can run. any thoughts ?

If only one car is on the track, sure. But if there are two cars, how do you tell which one is which? Existing timing systems solve this problem by using IDs on vehicles, using transponders. Look into the existing timing systems.

I finished my IR lap timer proyect some months ago. I was able to detect more than 2 cars at the same time, but I ended up buying lapmonitor lap counter as it was cheaper 😅

Take a look to this
https://www.rctech.net/forum/radio-electronics/1002584-rchourglass-diy-lap-timing-aka-cano-revised.html

10 clicker/counters mounted on a board... one operator........ aka 1980's RC racing.

If it is for just 1 car then a beam is enough. Look arround the internet and you will find enough diagrams and modules how to setup a long range beam with IR and even lasers.

In a far past I had made my own IR transponder mounting in the side of the body and a simple IR receiver. I was able to hook up the receiver its signal to a stopwatch but in that time with MSDOS it was easy to read signals on the printer port so I made a simple program in BASIC to count a 5 minute heat

try Lap trax its free. it will also work with a few cars.see I read ur 1st post.

laptrax is an awesome app, but you need to build and stand for the phone. Give it a try!

thanks for all the input...i remember hand counting in the 80's, good times back then. i was hoping to recreate what the SCCA did in parking lots way back when. i guess i'm just an old on road guy stuck racing off road in order to stay local. love the scale look the drifting guys go for but not the driving.

i build this ir lap counter based on lisergios ricino proyect , https://github.com/cdemetriadis/RiCino-Lap-Counter/wiki
and the rchourglass.
the ir lap counter works good and are cheap to build ,but if two cars passes at the same time it only counts one, this is due to the 8mhz clock of the attiny85 , a 16mhz external oscillator can be added to the attiny85 and run in TSOP7000 receiver , but i dont know how to do that .
the rchourglass I didn't right and I have poor signal detection