I am posting this again just to avoid
confusion in the user community. As mentioned earlier, the
radios have a built-in voltage regulator with a very wide operating range. About 8V up to 20V. There are some additional variables that
affect this. We have reduced all the complexities into a simple recommendation.
Our normal 12V power supply works well below 50
meters. And for cable length above 50 meters, use a power supply in the 15V -
18V range. http://www.smartbridges.com/new/products/ps.php.
This recommendation has enough margins so you don't have to get into very
detailed calculations on the cable voltage drop etc.
The soon to be released PoE
Outdoor unit will work for all cable lengths, new radios, and existing radios.
In addition it provides robust grounding and regulatory compliant Lightning
protection.
Hope this helps.
Nimesh
-----Original Message-----
From:
[EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brian Winter
Sent: Saturday, November 08, 2003 2:50 PM
To: [EMAIL PROTECTED]
Subject: Re: [smartBridges] 18v
power?
Noted and thanks. So fwiw:
Volts Ohms
Metres Feet
13 2.86
12.70 41.66
14 5.71
25.40 83.32
15 8.57 38.10
124.98
16 11.43 50.79
166.65
17 14.29 63.49
208.31
18 17.14 76.19
249.97
19 20.00 88.89
291.63
20 22.86 101.59 333.29
The 48v PoE must work by current sensing and adjusting the
voltage applied to suit the DC resistance. This is smart (sic) as it will
take all the other factors into consideration, incl temp variations of cables
and radio, different cable types and their DC resistance, whether using one leg
or two (one or both ways), RJ45 connectors (and how corroded they are !)
I guess then in answer to a previous posting, sB do have a
certified PSU for all cable lengths etc. Moving on .....
Just for a laugh. See how an 18v psu runs out of steam
at <80metres/~260ft (ie <12v available at the radio). This'll never
get to 300ft max mentioned earlier.
Note: Don't take this too seriously (although this is the
BEST it can get). I've assumed the radio behaves the same throughout the
range, and as already noted, thats not very likely - It'll probably "fry
and die" if its asked to disipate an extra 2.41W of heat on the
end of a short cable - Nice and cosy during the winter though. Also
taken no account of connectors etc
Volts Metres
Ohms Amps [EMAIL PROTECTED] Heat(W)
18 10
2.25 0.49 16.89 2.41
18 20
4.50 0.46 15.91 1.82
18 30
6.75 0.44 15.04 1.33
18 40
9.00 0.42 14.26 0.94
18 50
11.25 0.40 13.55 0.61
18 60
13.50 0.38 12.91 0.34
18 70
15.75 0.36 12.33 0.12
18 80
18.00 0.34 11.80
18 90
20.25 0.33 11.32
18 100 22.50
0.32 10.87
----- Original Message -----
Sent: Friday,
November 07, 2003 10:13 PM
Subject: Re: [smartBridges] 18v power?
> And it gets more complicated with Smartbridges. The
older models used 2
> wires up and 2 wires down for power. The newer models use 1 wire for power
> and one wire for reset and 2 wires for return. They also have the new 48
> volt POE injector that is supposed to be able to sense cable length and
> supply the correct voltage to the radio irregardless of cable length.
>
> John
>
> ----- Original Message -----
> From: "Brian Winter" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Friday, November
07, 2003 02:04 PM
> Subject: Re: [smartBridges] 18v power?
>
>
> > They can't "certify" this. It depends on the cable
you use and how good
> the
> > regulated supply is. Assuming a psu man enough for the task, Cat5
cables
> > will be similar so as a guide:
> >
> > Woodhead outdoors cat5 FTP and UTP 24 awg solid has DC resistance of
150
> > ohms/Km (at temperature +20C)
> > PoE uses 2 wires up, so half the resistance, and 2 wires back,
so double
> > that to get you back where you started.
> > APPO requires 350mA at 12v
> >
> > So working backwards, if you want to lose 1v (ie a 13v psu) at 350ma,
you
> > need 2.86 ohms: thats 19.05 metres (62.49 feet)
> >
> > Heres the rest:
> > Volts Ohms Metres Feet
> > 13 2.86
19.05 62.49
> > 14 5.71
38.10 124.98
> > 15 8.57
57.14 187.48
> > 16 11.43
76.19 249.97
> > 17 14.29
95.24 312.46
> > 18 17.14 114.29
374.95
> > 19 20.00 133.33
437.45
> > 20 22.86 152.38
499.94
> >
> > You can see why they don't bother quoting above 18v. 100+M of CAT5 is
> > getting a bit long !!
> >
> > In reality the APPO etc will have an on board regulator (they would
be
> > unlikely to get it certified without), so there'll be some
considerable
> > tolerance to this. DC resistance of cable and power requirement
of radio
> > will change with temp too.
> >
> > bw
> >
> > ----- Original Message -----
> > From: "Breiland, Derek" <[EMAIL PROTECTED]>
> > To: <[EMAIL PROTECTED]>
> > Sent: Friday,
November 07, 2003 5:07 PM
> > Subject: RE: [smartBridges] 18v power?
> >
> >
> > > Exactly, hence the need for certification. :)
> > >
> > > -----Original Message-----
> > > From: Hugh Carmichael [mailto:[EMAIL PROTECTED]
> > > Sent: Friday,
November 07, 2003 11:01 AM
> > > To: [EMAIL PROTECTED]
>
> > Subject: RE: [smartBridges] 18v power?
> > >
> > > My cable run is about 250 feet. I ended up using an 18V
adapter from my
> > > notebook PC. The SB site says 15-18V for runs longer than
180 feet.
> > >
> > > My question is do you use 15V at 200 feet, 16V at 225 feet, 17V
at 250
> > > feet etc. It seems like a pretty big gap between 12V to
18V to allow
> > > for an additional 120 feet (to the max of 300)
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: [EMAIL PROTECTED]
>
> > [mailto:[EMAIL PROTECTED] On Behalf Of Breiland, Derek
> > > Sent: Friday,
November 07, 2003 11:50 AM
> > > To: '[EMAIL PROTECTED]'
>
> > Subject: RE: [smartBridges] 18v power?
> > >
> > > It would be really nice if Smartbridges were to actually certify
at
> > > least
> > > one if not several power supply options.
> > >
> > > When we start talking about "be careful of the smoke"
we are just
> > > guessing
> > > and in this business there is no room for guess work. If
we had a
> > > certified
> > > product recommended from Smartbridges I think we would all feel
better
> > > about
> > > using it and in the event we needed support on a problem from
> > > SmartBridges
> > > we would know we are using certified equipment to rule that out.
> > >
> > > I am awaiting the release of the POE outdoor. Even though
I have no
> > > intentions on using it outdoors it does provide for a higher
voltage
> > > level
> > > for long cable runs as well as some surge protection the way I
> > > understand
> > > it. Not the cheapest solution but just like anything else
you get what
> > > you
> > > pay for.
> > >
> > > Something bothers me about going out to the local Radio Shack
for a
> > > power
> > > supply to run my AP's etc.. Not to knock Radio Shack but
this is a
> > > situation that needs a commercial grade type solution, not an
18VDC
> > > power
> > > supply intended for the general public.
> > >
> > > -----Original Message-----
> > > From: John Hokenson [mailto:[EMAIL PROTECTED]
> > > Sent: Friday,
November 07, 2003 1:29 AM
> > > To: [EMAIL PROTECTED]
>
> > Subject: Re: [smartBridges] 18v power?
> > >
> > > Mouser Electronics....
> > >
> > > JH
> > > ----- Original Message -----
> > > From: "Jeremy Oswalt" <[EMAIL PROTECTED]>
> > > To: <[EMAIL PROTECTED]>
> > > Sent: Thursday,
November 06, 2003 6:41 PM
> > > Subject: [smartBridges] 18v power?
> > >
> > >
> > > > Okay, I can't seem to find the articles in the archive
concerning
> > > where to
> > > > get an 18v DC power supply that works with the
Smartbridges. I know
> > > > Smartbridges is coming out with one, but I can't wait
another week. I
> > > need
> > > > two for a 170' run. Any recommendations?
> > > >
> > > > _____
> > > >
> > > > Jeremy
> > > >
> > > > _____
