just curious, does any of you know a good system for lap counting and of coarse cheap or is there any guide to biuld one? 'cause here it's kind of difficult to find one for rent under 200 dollars/race.

rclapcounter.com & dadsfunepage.com I myslef dreamed of this, good luck it will cost some bucks. The last address seems to be the most economical I have found and simple.

the last page that you put there is not working, for the first one i just wrote an email to them. but seems to be an expensive one system, i need like 13 sensors of those, and that's a little bit expensive, i think i will be like a 1000 dollars system, not that cheap.

Look up the robitronics lap counter on towerhobbies.com

well in fact i bought the one from dadsfunpage in the mean while, and then i will bought the one from rc lap counter, that last one is the best for the buck that i could found.

It's something to easy to make and REALLY overpriced. A microcontroller of $10 with the proper sernsors and independent clock can lap time up to 15 cars easily! I can design one but it will cost you more than $200 so go and get one once and for all...[8D]

ya know what weird, I make my own electronics (not servos)for RC's and it only takes $10-$15 to make and still works as good as good as some of those in stores except spread spectrum.

can any of you explain me with more detail how does the systems works, or how can i build one?

in a nut shell, the way it works is it takes a signal from the "transponder" and reads it and says ok 0101010101 is car A, and 001001001001001 is car B.... reading this "code" it if you wanted to make your own, you would need a "source of radio ID not powerfull at all since you want it to have a really short range, a reciever (a loop of wire), and a way to plug this into your computer for reading the data and saying what car had what time, as for making it, i rly can't say much[]

Well you should learn how to play with microcontrollers. And you also need as many LM555 timers as the cars you wanna time. If you already have the transponders it's easier. If not then you should make a transponder first. There's also a program that can do anything with input output systems: Labview from national instuments but it alone may cost you more than 4-5 expensive lap timing systems...

or maybe you can write a program that deccodes the different signals... ya, unless you can think up of an easy way to do it (different timmers spitting out the data on a printer or somethin), i have sadly no clue what to do, if you just want laps only and don't really care about times you can consider using the LM555 timer to make a pulse circuit and then have that transmit the weak signal that gets picked up, and gets decoded by a simple bandwith filter (make shure to have the bandwith different from that of the transmitters and have a large difference between them in frequency terms), and rig the outputs to a resetable counter unit and bingo there is a somewhat complex way to do things, ill try and get some pics of a transmitter reciever circuit working (maybe somethin intnded for ultrasonic range finding can work???)