[youtube:http://youtu.be/EXlDcKeUq14]
Racing toy cars, like Pinewood Derby or CO2 dragsters, is a lot of fun. But if you want to compare the results of multiple races, you need be able to accurately record the finishing times of each one. To do this, I designed a timer circuit that will automatically record the finishing times.
Two light sensors are mounted on a track. The first one is positioned just in front of the starting line. The second is located at the finish line. When the car crosses the first sensor, it starts the timer. Then when the car crosses the second sensor, it stops the timer. This lets you automatically record the finishing time of each car.
The system that I built is tailored to toy car races but it can easily be adapted for other kinds of races.
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What is the purpose of 555 in this circuit? I know 555 is a timer, is something to generate an oscillating signal, and I can’t see how it can be used in this circuit.
Wouldn’t it be easier to just use a transistor instead? The transistor would work as an on-off switch.
Are you powering the stopwatch using 9V?
Hi, what’s on the back cover? I took it out and broke it. where can I find a replacement. tnx
Can you add a switch or circuit for a winning lane light if using two of these (one for each lane)?
the circuit is not working :( i simulate the whole control circuit on protues ISIS .6 Professional 7.6 but ciruit not run
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This is completely useless!! There is no way to see how to make the breadboard!! Make a video about it!!
Hello:
I know you said “The two light sensors (photoresistors) need to be chosen so that each one has approximately the same resistance. The value of the series resistor (R1) should be about the same as the value of the two light sensors in parallel.”
But, could you give me any idea about the value of the photoresistor and R1 are?
Thank you in advance
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