RE: DC in Cat5

["Dr John Tankard" <john@xxxxxxx>]

There are several issues that you need to consider:-

1) voltage drop. Depending on the length of the cable you will not end
up with 9v at the other end perticuly if there is current draw

2) floating voltage levels. Check that the supplies you are using can
have 0v tied together

3) Risk of equipment damage. Some toys have no over current protection,
they rely on the fact that the supplied wart will not produce enough to
do damage


That said, I do it I distribute 9v throughout my house, it supplies :-

HomeVision
Several PIC lighting gadgets
Several SSR's about 20
RF Solutions RF receiver
Several Rabbits

I use a programmable power supply for this and I set the maximum current just beyond the maximum possible that the devices should use. If I
introduce a short, the supply will instantly switch from voltage control to current control in which case it lowers the voltage to a point where
the current is at the set maximum. There is a LCD display which shows
the current voltage currently 9.03 and the current currently 237mA. In
my case the maximum is 450mA (The RF system draws a lot when all
channels are in the on state)

The one I use also supports remote voltage detection, this is very
useful on long runs as you, use a second pair which has no current draw
it just senses the voltage, this means that the supply is tracking the
voltage at its destination not at the supply. (I don=92t actually use this<= BR> feature because the bit of kit I am most concerned about is the HV and
its located just a few feet from the supply

Theses supplies are more expensive than wall warts, mine cost about
=A3150, but I use it a lot when developing circuits, it saves the smell of<= BR> burning plastic. (Triple outputs are much more expensive =A3425)
John

> -----Original Message-----
> From: happy_hammer66 [mailto:bill.mcmahon@xxxxxxx]
> Sent: 12 April 2002 11:39
> To: ukha_d@xxxxxxx > Subject: [ukha_d] DC in Cat5
>
>
> instead of using multiple AC/DC converters for every little toy i get =
> and to improve presently low levels of WAF, i was thinking of having <= BR> > two or three central DC supplies at node 0 (set for various
> levels ie.
> 5V 9V 12V) and running the DC on pins 7 and 8 of the RJ45.
>
> Is this a no-no?
>
> The only problem i forsee is whether the amount of current you can > supply via cat5 cable is too low, but some of the toy's should draw > quite small amounts of power.
>
> I wouldn't think it would interfere with the data on pins
> 1,2,3,and 6. I would leave pins 4 and 5 alone incase someone
> plugged in a telephone
> and blew something up which would reset WAF back to nominal level.
>
> bill  
>
>
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