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Topic: Timer Circuit using a laser and an LDR? (Read 1 time) previous topic - next topic


Hey there! I'm pretty new to Arduinos and programming, but I am keen to get started on a project during the school holidays. I want to make a timing device for my mountain bike track using an arduino controller. My original thought was to have a laser being sent into a tube with a LDR at the end, and when a bike goes past, it will record a time.
Another idea was to have a starting beep sound, such as 3 low tones followed by a higher tone with one second intervals, perhaps coming from a Piezo transducer or small speaker.
I would really appreciate anyone who could tell me basic things such as coding help, as I have a decent understanding of electronics, just not good with programming.


Sep 03, 2011, 10:25 am Last Edit: Sep 03, 2011, 10:36 am by MikMo Reason: 1
For the laser LDR setup, all you need is to hook up the LDR togeter with a fixed resistor as a voltage divider to an analog pin, then constantly read the analog pin and wait for a large change in value. The tube has to be fairly deep to shield the LDR from fluctuations in ambient light levels. A photo transistor might be a better option than the LDR. It is switching faster and is probably not so sensitive to changes in ambient light levels.

For the beep, there's a tone function in the Arduino programming language you can use.'

I recomend breaking your project down into smallish tasks that can easily be build and tested individually, like laseer / LDR triggering, beeping, timing.

Make small test setups for each task, make it work, and in the end put it all together. This way it's much easier to find and fix errors.

The three things you want (laser/LDR - Beeping - Timing) has all been done many times, so you should be able to search the forum for lot's of usefull info.


Don't forget that you also need some way to display the time, like an LCD display, or by sending it to a PC.

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