i am working on a school project and need to design a circuit that will decode the time it takes once a light is triggered to the time it goes off (time to decode - TTD).. i have some ideas but i am somewhat of a newbie.. any help would be greatly appreciated.. -thank guys

 

We can help but you will have to explain a bit more clearly what you are attempting to do.

What do you mean by "light is triggered to the time it goes off"?

What level school work is this?

 

this is for my engineering class (undergrad)
we will be triggering a device that sets off a light that will remain on for a variable amount of time from 0-10sec (measuring only ms and sec)
We would like to count the time it takes once it is triggerd to the time it cuts off ex: light on - light off = .143ms
We are goin to implement a microcontroller and a light sensor and send the information via usb to our laptop
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What turns off the light?

 

its an external trigger which has already been configured

 

Use a photosensor and measure the duration that the sensor receives light.

 

ive had a few ideas, but not sure if theyd work.. 2 photo transistors.. maybe an LDR so the counter starts when light is on so the resistance drops using an opamp to bias transistor to relay

 

any ideas on how to design the circuit so it functions properly?

 

What relay? I thought you just wanted to measure the time the light is on.
Connect the output of the photosensor to an input pin of the microcontroller.

 

more or less yea... i just want to trigger the light, initiate timer.. light goes off.. stop timer.. send data to computer.. it just seems like there would be more to it then just that.. u made is sound so simple

 

If you want complicated ... try here.

 

If you want complicated ... try here.

I think the calculation delay might be toooooo long.

 

more or less yea... i just want to trigger the light, initiate timer.. light goes off.. stop timer.. send data to computer.. it just seems like there would be more to it then just that.. u made is sound so simple

The microcontroller is the timer, so you don't need a separate timer.