I am making a circuit that will pulse an LED on/off when a tone is present/absent from an iPod/iPhone. The iOS application can switch on and off a pure 10kHz signal with sub-millisecond precision. This will be used for high school kids to stimulate the neurons of genetically-modified fruit flies, you can read more here.
I am using the LM567 Tone Detector to switch the LED. The circuit is attached as an image. It works well, and switches on when the tone is played. Only there is a substantial delay between when the tone comes on to when the LED comes on I measured to be 15ms (or ~150 cycles). For my application, this must be much quicker: 2-3ms.
According to the spec sheet (also attached to this post), the Fastest ON-OFF Cycling Rate is:\(
{f_o}/{20}
\)
In my design, \({f_o}=10,000Hz\) therefore the switching rate should be \(10,000Hz/20 = 500 Hz = 2ms\). The documentation has a graph labeled "Greatest Number of Cycles Before Output". But I am struggling to understand what it means.
Has anyone ever used this chip? I am assuming that C2 may change the number of cycles required to change states, but would like to understand what that capacitor is doing. What does Bandwidth (% of Fo) mean in this situation?
Thanks for all your help. I love this board!
I am using the LM567 Tone Detector to switch the LED. The circuit is attached as an image. It works well, and switches on when the tone is played. Only there is a substantial delay between when the tone comes on to when the LED comes on I measured to be 15ms (or ~150 cycles). For my application, this must be much quicker: 2-3ms.
According to the spec sheet (also attached to this post), the Fastest ON-OFF Cycling Rate is:\(
{f_o}/{20}
\)
In my design, \({f_o}=10,000Hz\) therefore the switching rate should be \(10,000Hz/20 = 500 Hz = 2ms\). The documentation has a graph labeled "Greatest Number of Cycles Before Output". But I am struggling to understand what it means.
Has anyone ever used this chip? I am assuming that C2 may change the number of cycles required to change states, but would like to understand what that capacitor is doing. What does Bandwidth (% of Fo) mean in this situation?
Thanks for all your help. I love this board!
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