[mythtv-users] Update mythmobile pictures!

[Matthew Brichacek]

You bet, my father is an EE and we sat down for a couple days to get
this all figured out.  Although I ended up using a diff setup than we
originally designed I will try to explain as much of each one as I can.

First, let me start off by saying if you are going to use a regular MB
and not a laptop or other low-power board then I would suggest the power
supply at http://www.opussolutions.com/ .   I have one of these I can
sell you cheaper than they have online since I don't need it anymore,
but it's only the PCB and not the power supply with the casing.  It
hooks to the MB and sends it signals for on/off and it also has some
deep discharge circuits on it.  I ended up going with a deep cycle
marine battery in the truck just to avoid deep discharges.

The setup I have it pretty simple.  Two 10 gauge wires come off the
battery and go to the back of the truck.  Positive goes to the 50A relay
and then to the 12v supply, negative is hooked directly up to the 12v
supply.  There is also a signal wire that comes off the stereo and sends
a 12v signal whenever the truck is turned on/off.  I use this to trip
the 50A relay and it keeps the circuit closed while the truck is
running.  The same signal wire also goes to the 1shot relay and sends a
signal to the MB through some soldiered connections on the MB, this
turns the machine on when it's off.  When the signal is taken away
(truck turns off) the 50A relay circuit opens back up and takes away
power from the laptop.  When power is taken away an acpi event is
triggered to start a 10 minute timer as described in the first email. 
If the 50A relays circuit is closed again then that acpi event kills the
timer from the previous event and keeps the machine from turning off. 
If the 10 minute timer finishes, it executes a clean shutdown and the
process starts all over again when the truck is turned on through the
1shot signal.
If you aren't using a machine with an internal battery you could hook up
another timer relay that turns on when the 12v from the stereo is taken
away, that will keep power to your machine while you run a timer or just
do a quick shutdown.

Using a regular MB introduces some other problems to work around.  If
you want to put this all on a single PCB then you would need about 4
relays as well as some pretty heafty capasitors to hold your charge
while you shut down the machine.  I have this all put in a diagram and I
will try to find it and mail it to you off list, or post it on my server
so everyone can use it.  But again I have to suggest the opus system as
it was designed specifically for this, if your interested in grabbing
the one I have then message me off list.

Hope this helps, feel free to ask more questions.

Matt


On Sun, 2003-06-22 at 15:40, Max wrote:
> Maybe this is getting a bit too offtopic, but can you provide more
> information about the relay circuit, I've been meaning to do exactly this
> kind of a setup for another project, and this may save me from re-inventing
> the wheel.
> 
> -M
> 
> 
> 
> 
> ----- Original Message ----- 
> From: "Matthew Brichacek" <mmbrich at customlinuxsolutions.com>
> To: "Discussion about mythtv" <mythtv-users at snowman.net>
> Sent: Sunday, June 22, 2003 2:25 PM
> Subject: Re: [mythtv-users] Update mythmobile pictures!
> 
> 
> > I bought the 12v power supply for the omnibook and have it wired
> > straight into the battery and the 50A relay turns on and off the power
> > to the 12v supply (gets a signal from the stereo when the truck is
> > turned on).
> 
> 
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