Re: H/W Development question

[ian.bird@xxxxxxx]

> What I'm not sure is how to start designing something simple that
I
> could connect to a serial port to monitor this.

This sounds like an open collector output which effectively sinks
current
i.e. goes to 0v. Any connected voltage will also be dragged to 0v
assuming
the current flow is not too high (see the specs cos it is usually not
that
big). The fact that it is 13v otherwise means there is a pull up
voltage
present at the alarm end of things - just gives a nice swing from one
extreme to the other and avoids floating lines.

To monitor this (one of many ways) would be to have this connected to a
micro which runs a program that sends a serial message when the state
changes. You could monitor several ports this way and add in lots of
other
goodies if you felt like it.

I am sure there are lots of other ways to do this but this is one I
know.
You could also opto isolate the micro from the alarm ports as well very
easily.

> is USB development that much harder ?
Apparently it is a bit of a pig developing USB drivers. I use a USB to
serial adapter which appears to the PC as a virtual serial port which
works
quite nicely. Some serial devices don't like these but home brew seem
OK
for the most part.

HTH

Ian





                                                                                                                                
                     
"Robert
Welsh"                                                                                            
                     
<bob-ukha@suburba       
To:      
<ukha_d@xxxxxxx>                                               
                     
nwire.com>              
cc:                                                                              
                                              
Subject:  [ukha_d] H/W Development
question                                      
                     
06/12/02
09:48                                                                                            
                     
Please respond
to                                                                                         
                     
ukha_d                                                                                                    
                                                                                                                                
                                                                                                                                




One for the hardware techies out there...

I discovered last night that my alarm system has a number of output
terminals which can be use to drive external devices e.g. ARC or
diallers.

One of the terminals is a "set" indicator - which is exactly what
I'm
looking for.

This terminal is 12V normally and drops to 0V on "set"
condition.
There's also a 13V and a 0V terminal offered on the PCB.

What I'm not sure is how to start designing something simple that I
could connect to a serial port to monitor this.
It seems to me that it's probably the kind of thing that must have been
developed 100 times by 100 different people.

Any pointers would be appreciated.

Robert
(fundamentally a software guy, with a rusty hardware background)

PS - Most developments I see around use RS232 ports....is USB
development that much harder ?



http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx
Subscribe:  ukha_d-subscribe@xxxxxxx
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
List owner:  ukha_d-owner@xxxxxxx
List of UKHA Groups here - http://groups.yahoo.com/group/UKHA_Grouplists/

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/








http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx 
Subscribe:  ukha_d-subscribe@xxxxxxx 
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx 
List owner:  ukha_d-owner@xxxxxxx
List of UKHA Groups here - http://groups.yahoo.com/group/UKHA_Grouplists/

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.