tag:blogger.com,1999:blog-6053337542597571017.post3952367783003684425..comments2024-03-28T12:12:05.050+01:00Comments on Hack Correlation: Auto on-off for amplifierLigiushttp://www.blogger.com/profile/04631687424641789584noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-6053337542597571017.post-56415502484198445972017-02-07T16:01:04.467+01:002017-02-07T16:01:04.467+01:00There are two things to watch out for:
DC bias on...There are two things to watch out for:<br /><br />DC bias on signal is fine, you just need a coupling capacitor in series, a resistor to limit the current and the ADC should likely use only the positive signal (rectification through protection diodes). Or you can add a diode to feel safer.<br /><br />DC offset on ground is a more complicated topic. On most car audio gear the audio ground is sitting at half the supply voltage. You WILL blow up the MCU if you try to connect it without protection.<br />The best solution is to use an audio transformer, feed the signal from the transformer into MCU ground and ADC.<br />The other solution is a capacitor in series with the signal ground, but you will be creating a ground loop that feeds noise back into the audio system. I also don't know what the frequency response of a system like this would be.<br />The third solution is a differential amplifier or comparator. This you can feed directly into an I/O pin instead of using ADC. IN+ goes to signal, IN- goes to signal ground, output to MCU. You will need some low-pass filtering, gain adjustments and hysteresis. Search for LM324 schematics.<br /><br />Hope that helps, it's a topic in itself and hard to cover. Plus, I'm not knowledgeable enough to give better advice.Ligiushttps://www.blogger.com/profile/04631687424641789584noreply@blogger.comtag:blogger.com,1999:blog-6053337542597571017.post-31136431731374920732017-02-07T10:55:55.286+01:002017-02-07T10:55:55.286+01:00Thank you for your post!
It was interesting to re...Thank you for your post! <br />It was interesting to read. I'm going to repeat it for personal use.<br />I would like to make small changes to the design - connect a second audio channel to the ADC input #3 (PB3) with appropriate changes in the MCU code.<br />The only confuses for me - presence of DC bias 3.6V on this input from the USB con. circuit.<br />What do you think, is it possible to compensateit in the code?Yevgeniyhttps://www.blogger.com/profile/04160699775468174367noreply@blogger.com