May 23, 2011
about 4 years ago
I’ve been playing with these and yes you should be able to drive the LM3914 series of chips OK. Each output is fairly linear over 25db. But be aware that the output is refenced at around 500mv, so for best results use an rail to rail opamp to ground reference the output. You would connect the output of the MSGE7 to the positive input of the op amp. Place a 1K resistor from opamp output to negative input. Then connect a 50K pot from negative input to +5V, adjust pot for 0 volts out with no audio input to the MSGE7.
If you want to run standalone (no micro), things become complicated. You would need to use an analog switch to demux the output into seven outputs. Each output would drive a separate LM3916. This would require a 1 of 8 decoder to drive the analog switch and a divide by seven counter circuit to drive the 1 of 8 decoder (eighth output is not used). The counter would divide the strobe pulses from the timer.
The timer which drives both the counter and the MSGE7 strobe input could be a LM555. To avoid flicker, set the timer to produce a low duty cycle positive pulse. To adjust decay of display adjust the timer frequency higher for faster decay.
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