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Sending data over 24VDC

 
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Guest
Sending data over 24VDC
PostPosted: Tue Oct 04, 2005 5:39 pm     Reply with quote
Hi !

I looking to send data to turn on relay on 24V dc 2 wires

I have only 2 wire on the building to give power to pic and photo sensor and send back data to turn on relay ?

Thanks for your help

Alain Tanguay
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Tue Oct 04, 2005 6:31 pm     Reply with quote
I think you need to do a little more explaination of the system.

If you want an example of a system that communicates over 2 wires and is also powered over those same wires, look at DALI
Guest
PostPosted: Tue Oct 04, 2005 7:08 pm     Reply with quote
Yes , communication and power 24Vdc on same 2 wires
kender



Joined: 09 Aug 2004
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PostPosted: Tue Oct 04, 2005 7:11 pm     Reply with quote
Mark wrote:
... look at DALI


Mark, could you give a link to this system?

A similar problem - power and signal on one pair of wires raises, when one has to power an active antenna. It's usually solved with a bias-T. Potentially the system coud look like this:

Code:

      +24V ->                     -> EMI
              [bias-T] -> [cable]
data*clock ->                     -> [bias-T] -> [rectifier&filter] -> [comparator] -> data
                                              -> +24V
Mark



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Posts: 2838
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PostPosted: Tue Oct 04, 2005 8:08 pm     Reply with quote
http://www.dali-ag.org/
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1999&ty=&dty=&section=&NextRow=&ssUserText=dali&DesignDocSelect=
http://www.freescale.com/files/microcontrollers/doc/ref_manual/DRM004.pdf?srch=1
APES
Guest
BIAS T
PostPosted: Thu Mar 23, 2006 2:04 pm     Reply with quote
WHat is a BIAS T

I am working on same kind of project , power and comm over power line ,
kender



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Re: BIAS T
PostPosted: Thu Mar 23, 2006 2:58 pm     Reply with quote
APES wrote:
WHat is a BIAS T


Bias-T is essentially just one capacitor and one inductor connectd like this:

Code:

                    C1
modulated signal  --||---------
                               |
                               |
                               |
                               +------------- combined power and signal
                               |
                    inductor   |
                    L1         |
DC power supply ----OOOO-------


It can be used for combining DC power (or low frequency power, like 60Hz or 400Hz) with a higher frequency signa. Bias-T is typically used for providing DC power to the RF amplifiers over coax cables.
Apes
Guest
BIAS t
PostPosted: Fri Mar 24, 2006 1:34 pm     Reply with quote
Thank for the reply

I guess we called our BIAS T a coupling ckt
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