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I want to make a circuit that powers a transistor when a sound above a set threshold is reached. (Trigger a flash for high speed photography.)

How long will the response time be?

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  • $\begingroup$ It depends. The microcontroller clock is 16Mhz so a tight loop in assembly polling one input and triggering another can probably respond in less than a microsecond or even less than 500ns. Most likely it will be something else that limits your performance. If you show us a circuit and some code we can give you a more accurate estimate. $\endgroup$
    – Guy Sirton
    Mar 17 '14 at 5:08
  • $\begingroup$ @GuySirton I ask because I'm interested in knowing if it will work or not before spending any money on it. So you're saying that if my code is good enough, it will be really fast. I'm experienced with programming on the computer, so that shouldn't be a problem. Thank you for your comment! If you are certain it will be less than a microsecond, you should add an answer, and I'll accept it. $\endgroup$ Mar 17 '14 at 13:34
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If you're using a microcontroller (Arduino-type) with a loop, you can expect a response time of microseconds or less. If you're using a more advanced controller (Raspberry PI or BeagleBone Black), the latency will be less predictable, but very fast. The reason for less predictable latency is multitasking on the systems running Linux, while the Arduino isn't running anything that will interfere.

Given that you plan to use sound as a signal, there will be physical factors that create greater variation in reaction speed; wind direction comes to mind as a significant source of latency.

Of course, if you're trying to trigger it by the camera click sound, I guess you could do quite well with a simple arduino.

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Why would you use an Arduino plus a circuit when you can just use the circuit by itself? Here are some example circuits:

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  • $\begingroup$ Designing a circuit for it would be better. The only problem is I don't know electronics yet. I'm reading a 1400 pages book on it, but it takes time. $\endgroup$ Mar 17 '14 at 14:38
  • $\begingroup$ From your question, it sounds like you're already planning to build a circuit -- starting with the transistor that the microcontroller would signal. These circuits come pre-designed, and you'd just be buying the parts & assembling them. $\endgroup$
    – Ian
    Mar 20 '14 at 13:17

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