Here is a schematic I have made, it takes an audio input from a cell phone, puts it through the MT8870 that outputs binary, and put the binary output through a CD4028 for a BCD output. I think the guts of it are correct (audio to binary works fine on breadboard).
http://i45.tinypic.com/2d6hxd.jpg
JP1 and JP2 are generic pin headers for external connections, no specific application, just a digital out. Then there is a resistor array and LED indicators.
The pot R4 is (I think) used to change the sensitivity of the MT8870, so signals with low peak voltage will be best read with a lower resistance, and signals with a higher peak voltage is best with a higher resistance. The 1K resistor is there in case the pot is set to 0 ohms.
With the leftover in/out on the darlington, I may just put the binary outputs on those just in case it is needed for something.
First, is the 1k resistor to "protect" necessary?
Second, the incoming audio signal is stereo. Should I combine the two signals into one, or only just use one as shown in my schematic? If I were to combine the signals, can I just connect both the left and right signals together?
http://i45.tinypic.com/2d6hxd.jpg
JP1 and JP2 are generic pin headers for external connections, no specific application, just a digital out. Then there is a resistor array and LED indicators.
The pot R4 is (I think) used to change the sensitivity of the MT8870, so signals with low peak voltage will be best read with a lower resistance, and signals with a higher peak voltage is best with a higher resistance. The 1K resistor is there in case the pot is set to 0 ohms.
With the leftover in/out on the darlington, I may just put the binary outputs on those just in case it is needed for something.
First, is the 1k resistor to "protect" necessary?
Second, the incoming audio signal is stereo. Should I combine the two signals into one, or only just use one as shown in my schematic? If I were to combine the signals, can I just connect both the left and right signals together?
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