<div dir="ltr"><div><div><div><div>Hi Adam, <br><br></div>Thank you for your comments, We were aware of this.<br><br></div>That being said it is something we will need to ensure we have noted, so no one damages other equipment. <br><br></div>Regards<br><br></div>Robert Manietta<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Apr 18, 2017 at 11:23 PM, Adam Nielsen <span dir="ltr"><<a href="mailto:a.nielsen@shikadi.net" target="_blank">a.nielsen@shikadi.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Robert,<br>
<br>
> Please see our grant application for constructive comment and review.<br>
<br>
This might not be relevant for your purposes, but are you aware that<br>
the TP-Link TL-SG1008P switch you are proposing is a non-isolated PoE<br>
switch?<br>
<br>
This means that any device it powers cannot be connected to any other<br>
earthed device, or it will short out the switch's power supply. The<br>
reason is that (no doubt for cost cutting measures), any PoE devices<br>
connected to this switch have their negative supply (GND) connected to<br>
-48VDC with respect to earth, rather than the more usual direct<br>
connection to earth itself.<br>
<br>
The end result of this is that, should you power your Pi via PoE, all<br>
the connector shields on the Pi are sitting at -48VDC. So when you<br>
(for example) plug in a HDMI cable connected to a TV, the 0V shield on<br>
the cable gets connected to -48VDC on the Pi, short circuiting the<br>
brick powering the TP-Link switch.<br>
<br>
I had this exact problem and connecting a HDMI cable to the Pi produces<br>
a spark and shuts off the switch, although the switch does reboot once<br>
the cable is removed again. Although I didn't leave it connected for<br>
long enough to see if the power supply exploded or caught fire...<br>
<br>
If you will only ever be powering PoE devices that do not plug into any<br>
other powered device (e.g. VoIP phones, IP cameras, etc.) then you can<br>
probably get away with it, but I am a bit wary of my TP-Link switch now<br>
after this experience. I have to remember that any PoE device<br>
connected to this switch absolutely cannot have certain things plugged<br>
into it - HDMI monitors, powered USB hard drives, headphone cable to<br>
an amplifier (48 volts on an amplifier's audio input, ouch!)<br>
<br>
I would recommend looking at eBay for a second hand Cisco switch<br>
instead, which is what I ended up getting to replace the TP-Link when<br>
I eventually needed more than eight ports. You can get a 48-port PoE<br>
switch for $16 more than one TP-Link unit if you are willing to settle<br>
for 100Mbps on all switch ports, or if you want gigabit then a 48-port<br>
Cisco is ~$7 less than the three TP-Link 8-port switches in your<br>
proposal - not bad for double the capacity.<br>
<br>
I was a bit fearful of using a Cisco switch, thinking I'd have to take<br>
a course to figure out how to use it, but setting it up is one of the<br>
easiest things I've ever done. Installing Linux is way harder. It<br>
doesn't actually need any configuration at all if you want to use it<br>
like an unmanaged switch. I love how the configuration is just one big<br>
text file, which you pretty much just copy onto the device and it<br>
immediately starts functioning exactly as described. OpenWRT and the<br>
other router distros could learn a thing or two from that!<br>
<br>
Anyway, I just thought I had better point out one of the limitations<br>
with the TP-Link in case it affects what you were intending to do with<br>
it.<br>
<br>
Cheers,<br>
Adam.<br>
</blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><p style="margin-bottom:0.0001pt"><b><span style="font-size:9.5pt;font-family:Arial,sans-serif">Regards</span></b><span style="font-size:9.5pt;font-family:Arial,sans-serif"></span></p><p style="margin-bottom:0.0001pt"><span style="font-size:9.5pt;font-family:Arial,sans-serif"> </span></p><p style="margin-bottom:0.0001pt"><b><span style="font-size:9.5pt;font-family:Arial,sans-serif">Robert Manietta</span></b><span style="font-size:9.5pt;font-family:Arial,sans-serif"></span></p><p style="margin-bottom:0.0001pt"><span style="font-size:9.5pt;font-family:Arial,sans-serif"> </span></p><p style="margin-bottom:0.0001pt"><b><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#00b050">Please consider the environment before printing this email.</span></b></p><p style="margin-bottom:0.0001pt">
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