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<body class='hmmessage'><div dir='ltr'><font style="" color="#000000" face="Tahoma,sans-serif">Sam,<br><br> This power supply was mentioned as being good and used by several BBB owners -<br><br><a href="http://www.ebay.com/itm/Waterproof-DC-DC-Converter-12V-Step-down-to-5V-3A-15W-Power-Supply-Module/221117981188?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D27538%26meid%3D988493afeb074ee58054fe9bb314e6bb%26pid%3D100005%26prg%3D11353%26rk%3D1%26rkt%3D6%26sd%3D221605016721&rt=nc" target="_blank">http://www.ebay.com/itm/Waterproof-DC-DC-Converter-12V-Step-down-to-5V-3A-15W-Power-Supply-Module/221117981188?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D27538%26meid%3D988493afeb074ee58054fe9bb314e6bb%26pid%3D100005%26prg%3D11353%26rk%3D1%26rkt%3D6%26sd%3D221605016721&rt=nc</a><br><br id="FontBreak"></font><br><b><font style="font-size:16pt;" size="4">73 Doug</font><font style="font-size:16pt;" size="4"><br></font><font style="font-size:16pt;" size="4">WA3DSP</font><font style="font-size:16pt;" size="4"><br></font><font style="font-size:16pt;" size="4">http://www.crompton.com/hamradio</font></b><font style="font-size:16pt;" size="4"><br></font><br><br><div><hr id="stopSpelling">Date: Fri, 6 Feb 2015 22:58:09 -0800<br>From: kj6qfs@gmail.com<br>To: arm-allstar@hamvoip.org<br>Subject: Re: [arm-allstar] 12V to 5V DC-DC Converters?<br><br><div dir="ltr">David/ Everyone,<br><div>Which switching DC-DC converter should I be using for my BBB? I Have a URI and four USB-Serial adapters connected, so I'd like to come up with an adequate power supply. </div><div><br></div><div>Thanks and 73<br><br>Sam Skolfield<br>KJ6QFS</div><div class="ecxgmail_extra"><br><div class="ecxgmail_quote">On Thu, Nov 20, 2014 at 8:41 PM, David McGough <span dir="ltr"><<a href="mailto:kb4fxc@inttek.net" target="_blank">kb4fxc@inttek.net</a>></span> wrote:<br><blockquote class="ecxgmail_quote" style="border-left:1px #ccc solid;padding-left:1ex;"><br>
Hi Tom,<br>
<br>
Thanks for sharing your schematic. I've noticed one area of concern, which<br>
has personally bit me before. You should add a capacitor (perhaps 1uF or<br>
larger) very near the input of the LM7806. These little regulators are<br>
wonderful except when they decide to oscillate. And, that can happen, I<br>
promise--(Hind sight: 20/20 in my case!). Even if your regulator is well<br>
behaved, others might encounter problems if they try to duplicate your<br>
design, due to subtle variations.<br>
<br>
Also, note that the TIP110 transistor is rated for a maximum base-emitter<br>
voltage of 2.8VDC. So, your results many vary from device to device.<br>
Under variable load, the voltage regulation probably won't be perfect.<br>
<br>
A simpler linear regulator would be to use an LM7805T directly (including<br>
input and output bypass capacitors). They're capable of at least 1A output<br>
directly and will power a BBB okay...They will need a heatsink with a 12v<br>
input source.<br>
<br>
The primary reason I bring all this up is that BBB's are VERY sensitive to<br>
any power supply instability. The best, inexpensive, solution I've found<br>
is a small switching DC-DC converter like those already mentioned.<br>
<br>
<br>
73, David KB4FXC<br>
<div class="ecxHOEnZb"><div class="h5"><br>
<br>
<br>
On Thu, 20 Nov 2014, k5tra wrote:<br>
<br>
> 'Looks like the attachment didn't make it onto the list. Here's a link:<br>
><br>
><br>
><br>
> <a href="https://dl.dropboxusercontent.com/u/97484437/BBB%20Regulator%20%26%20Fan%20C" target="_blank">https://dl.dropboxusercontent.com/u/97484437/BBB%20Regulator%20%26%20Fan%20C</a><br>
> ontrol.jpg<br>
><br>
><br>
><br>
</div></div><div class="ecxHOEnZb"><div class="h5">> Tom / K5TRA<br>
><br>
><br>
<br>
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</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="ecxgmail_signature">KJ6QFS<br>Sam Skolfield</div>
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