Any electronics experts out there please?

  csqwared 19:38 05 Jun 08

I'm looking for help with a project please. Part of my work entails a little bit to do with road safety and we visit various media events promoting this. As part of our display I am considering a small Scalextric track fitted with safety (speed) cameras challenging the public to get round as fast as possible without triggering one. Many, many years ago I dabbled in home electronics and have a rough idea what I need bit I'm now stuck. My idea was to have a monostable timer (555), triggered by the brushes on the front of the car, sending an output pulse to an "AND" gate. The other half of the "AND" gate would receive an input from the brushes a little further up the track. If the initial (timed) pulse was still high when the second pulse arrived the output of the "AND" gate would switch on a transistor which would "flash" a small bulb/LED. I'm O.K. with the 555 timer circuitry but am totally lost after that in terms of the right components and how to connect it all up. Any help would be greatly appreciated.

  grey george 20:52 05 Jun 08

Sounds rather tricky to get the contacts in the right place with the cars passing over it. The pulse would drop to zero almost in an instant. You try posting to this forum they should have more expertese click here

  csqwared 21:24 05 Jun 08

Thanks for that. I'll give them a try. I did think that the 555 timer, once triggered, would hold the output high for the timed period but I'll see whgat they say. Thanks again.

  octal 21:31 05 Jun 08

Why not put a little magnet in the car and reed relays below the track which starts a binary counter and another set of contacts further along the track to stop the counter. I built a similar project a few years ago to measure the speed of a bullet, it worked extremely well.

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