[MLB-WIRELESS] Voltage Regulator-- 12v to 9v

[Tony Langdon]

Don't forget to put appropriate bypass capacitors between the input and
ground and the output and ground(0.1 - 1 uF should do the trick - use
monolithic or tantalum).  These regulators have a tendancy to self oscillate
in the MHz region if long leads are used and they are not bypassed.

Tony Langdon
Systems Development and Support
ATC Training Australasia.  Level 1 310 King St Melbourne 3000.
Phone:  1300 13 1983   WWW:  http://www.atctraining.com.au


> -----Original Message-----
> From: Andy Freeman [mailto:Andy.Freeman at jc.com.au]
> Sent: Tuesday, 12 March 2002 14:31
> To: melbwireless at wireless.org.au
> Cc: 'Robert Farrar'
> Subject: [MLB-WIRELESS] Voltage Regulator-- 12v to 9v
> 
> 
> The question was asked...
> 
> "how do I get 9 volts at the access point instead of 12 volts?"
> 
> The answer is a voltage regulator.  Dick Smith sell a nice 
> little 3 pin
> package that will accept up to 30VDC input and output 9VDC.  The Dick
> Smith catalogue number is [Z6550] and the regulator has the markings
> [7809CT]
> 
> Below is a (fairly crummy) ascii drawing of how to wire one...
>      
> 
>     ----------
>     |        | 
>     | 7809ct |
>     |        |
>     |        |
>     ----------
>     ||  ||  ||
>     ||  ||  ||
>     ||  ||  ||
>     ||  ||  ||
>     ||  ||  ||
> 
>     1   2   3
> 
> If you called the pins 1,2,3 from left to right then the following
> applies:
> Pin 1. Positive 12v in
> Pin 2. Negative 12v in (and negative 9v out)
> Pin 3. Positive 9v out
> 
> So just run your PoE at 12volts to the end of the CAT5, at the access
> point end add a regulator to drop the 12v to 9v.
> 
> 
> The cost?  AU$1.35 each inc GST!!!  You might want to add a 
> heatsink to
> that though, when you drop voltage it has to go somewhere and that is
> out of the regulator in the form of heat.  The regulator has a screw
> hole to mount a heatsink off.
> 
> 
> Cheers,
>                Andy.
> 
> andy at geelong.wireless.org.au
> 
> 
> 
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