 USB charging, Thinking about adding 5volts |
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| worn |
 Dec 9 2015, 07:39 PM
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Winner of the Utah Twisted Joint Award  Group: Members Posts: 3,560 Joined: 3-June 11 From: Madison, WI and North Bend WA Member No.: 13,152 Region Association: Upper MidWest 
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I got a bunch of USB sockets and voltage regulator ICs that will trim 12v to 5v, and thought it would be nice to wire in for charging phones etc. someone suggested that the ICs would fry due to transients. So I am wondering about wiring zener diodes as shunts across the feed and wanted to know what you thought. I am especially interested in voltage and wattage for the zener and perhaps resistance to limit current. Thanks!
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| Spoke |
Dec 11 2015, 12:07 PM
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Jerry Group: Members Posts: 7,370 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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The ready-to-go solutions noted are the easiest ways to get USB power.
If you want to design your own, the 7805 should work well. It is generally accepted in modern cars that 35-40V input voltage capability is adequate. This is partially because modern alternators have power zener diodes to limit the load dump (ISO7637-2, pulse 5) to 35V or so. Further overvoltage protection could be accomplished not with a zener diode but a transient voltage suppressor (TVS). I use TVS's on my front LED boards to protect the blanking circuits. You should also install a series diode to protect the 7805 against reverse battery application. The 7805 provides 70dB of attenuation of noise on +12V to provide a quiet +5V output. Filter caps near the 7805 are a good idea. I highly doubt the USB power would be affected much by noise on +12V line. Audio units are more susceptible since they use +12V directly. The Ultra caps should only be used to provide instantaneous energy for bass and subwoofer applications. |
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| stugray |
Dec 11 2015, 03:43 PM
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Advanced Member Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
QUOTE(Spoke @ Dec 11 2015, 11:07 AM)  The Ultra caps should only be used to provide instantaneous energy for bass and subwoofer applications. The only reason I suggested the UltraCap is that I know they are available at walmart. And they would definitely provide noise filtering, but are way overkill. Some of us don't have any kind of electronics store nearby since a lot of the Radio Shacks closed. |
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| Spoke |
Dec 11 2015, 03:56 PM
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Jerry Group: Members Posts: 7,370 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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QUOTE(stugray @ Dec 11 2015, 04:43 PM) QUOTE(Spoke @ Dec 11 2015, 11:07 AM) The Ultra caps should only be used to provide instantaneous energy for bass and subwoofer applications. The only reason I suggested the UltraCap is that I know they are available at walmart. And they would definitely provide noise filtering, but are way overkill. Some of us don't have any kind of electronics store nearby since a lot of the Radio Shacks closed. We think alike; We should hang out together sometime; We could get lost in conversation others would find boring. (IMG:style_emoticons/default/beerchug.gif) |
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Posts in this topic
worn USB charging Dec 9 2015, 07:39 PM
Mike Bellis
I got a bunch of USB sockets and voltage regulato... Dec 9 2015, 08:06 PM McMark Just buy a cigarette light USB, cut it open and ta... Dec 9 2015, 08:19 PM stugray What McMark said.
I just bought a female cigarett... Dec 9 2015, 08:28 PM
worn
What McMark said.
I just bought a female cigaret... Dec 10 2015, 11:06 AM Steve How many do you need? My stereo has one in it and... Dec 10 2015, 11:10 AM GregAmy $8 shipped.
http://www.amazon.com/Outlet-Cha... Dec 10 2015, 11:24 AM worn
$8 shipped.
http://www.amazon.com/Outlet-Ch... Dec 10 2015, 11:47 AM Steve Pratel
$8 shipped.
http://www.amazon.com/Outlet-Ch... Dec 11 2015, 08:55 AM stugray The 7805 should work fine in this car as long as y... Dec 10 2015, 12:51 PM worn
The 7805 should work fine in this car as long as ... Dec 10 2015, 01:54 PM stugray The audiophiles THINK the ultra capacitors help th... Dec 10 2015, 03:52 PM Mark Henry If you're willing to wait a month on shipping,... Dec 12 2015, 12:32 AM worn
If you're willing to wait a month on shipping... Dec 16 2015, 01:18 PM |
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