Comments on: Sound Should Just Come Out Of It https://blog.nearfuturelaboratory.com/2012/01/17/sound-should-just-come-out-of-it/ Clarify Today, Design Tomorrow Fri, 18 Aug 2017 17:58:24 +0000 hourly 1 https://wordpress.org/?v=5.5.1 By: Julian https://blog.nearfuturelaboratory.com/2012/01/17/sound-should-just-come-out-of-it/#comment-661 Thu, 19 Jan 2012 06:55:28 +0000 http://nearfuturelaboratory.com/?p=6618#comment-661 In reply to LPM.

Seriously — your comment is super helpful. I’m okay with digital circuit design, but the analog stuff was never my strength, so this really helps.

So basically — yeah..if you wouldn’t mind drawing the schematic, that’d be really helpful. I believe I’m following you — but it’d be nice to be sure!

]]> By: LPM https://blog.nearfuturelaboratory.com/2012/01/17/sound-should-just-come-out-of-it/#comment-660 Wed, 18 Jan 2012 17:53:03 +0000 http://nearfuturelaboratory.com/?p=6618#comment-660 Basically all I’m suggesting is to replace the comparator of your first circuit with a transistor. Use the pull up you already have to turn the transistor “on” when the plug is disconnected. With the transistor “on” CE will be pulled low and the switcher will be shut down. When you plug in the connector will pull the gate (or base) low and shut the transistor off. With the transistor off a weak pullup on CE will cause it to go high again and turn the switcher on. Sorry if that isn’t clear, if you still don’t get what I mean, I’ll take the time to draw a schematic when I’m at home and have a real mouse, its not complicated.

BTW I hope you realize that when the switcher turns off the Vout goes to Vbatt not GND. Trace the DC path from the battery, through the inductor, through the diode to the output. If you have loads connected to this rail they may half power on and act strangely or continue to draw current and run down your battery. In this case we’d need at least two transistors to fix that. (…or we can use your circuit B)

Just in case the tone of my first wasn’t clear I’m really just trying to help out, I’m not trying to tell you how to build your circuit or anything. My “what happens” question was a sincere question. I really don’t know, could be fine, could be really bad. I always get antsy when my system touches someone else’s system. Anyhow, I just noticed that there could be problems with your setup you haven’t considered and wanted to at least mention them in case they would save you some pain later on.

Good Luck!

]]> By: Julian https://blog.nearfuturelaboratory.com/2012/01/17/sound-should-just-come-out-of-it/#comment-659 Wed, 18 Jan 2012 15:35:20 +0000 http://nearfuturelaboratory.com/?p=6618#comment-659 In reply to LPM.

Help! Draw me a circuit!

]]> By: LPM https://blog.nearfuturelaboratory.com/2012/01/17/sound-should-just-come-out-of-it/#comment-658 Wed, 18 Jan 2012 14:50:31 +0000 http://nearfuturelaboratory.com/?p=6618#comment-658 I don’t think this is as good idea as you do. The pin in the connector that gets pulled to ground is going to be floating up at the battery voltage and it looks like it will take an inrush current into the switcher’s bulk cap to pull it to ground. What happens when you plug your expensive audio equipment into the jack and the audio contact gets a jolt of current slammed into it because you wiggled the connector too much as you plugged it in? 20 cents worth of two resistors and a cheap bjt can make that pin high impedance and then you won’t have to worry about it. That would be my preference.

Somewhat generally, I find switched grounds are easy to build CAN be problematic. Ground is everywhere and from a reliability standpoint it’s easy for a short to fall across a switch and improperly turn your circuit on.

Good luck.

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