[COLUG] Re: time to race

[Jim P]

Greg <capncrunch at woh.rr.com> wrote:

> From: "Jim P" <jep200305 at columbus.rr.com>
> > Laptops have builtin UPSs.  Cheap 12VDC to 120VAC inverters make
> > it easy to run them indefinitely off of a car battery without killing
> > the car.

> Most, in fact all clubs I've ever been involved with, have a trailer or
> box van that is used as a timing vehicle.  

Great!  

> They are equipped with some
> form of generator  to supply the AC power needed.  

Yuch!  What do they need that much power for?  Air conditioning?  
No wonder power is unreliable.  Tell them to get a UPS.  

> > So you are going to add a keyboard and display to your box?
> > Your complexity and cost just went up much.
> 
> No, I'm not being very clear.  I need to have a LCD or LED display
> (think 6 digit readout) to display the time as the car triggers the
> finish light...A FIFO buffer big enough to handle 3 times.  

If you want to have a prayer of running it on batteries, 
you will avoid LED.  Use an LCD module, possibly with 
momentary switch to turn on LED backlight.  
Plenty are available from many vendors.  Most of them use 
the same style interface.  You'll byte/nybble bang it.  
A 4*20 could display several times at once, hopefully 
avoiding the need for buttons to navigate.  

Here's one of many vendors of LED modules.  
http://www.allelectronics.com/cgi-bin/category.cgi?category=365&type=store

> > The CPU sucks gently, but the MAX232 will suck your battery dry.
> > If the 9V battery is just for back up, then it's great.
> 
> The 9V is just in case of a power loss.

I understood that.  9V batteries do not supply much current.  

At some point, folks just get to make another run for free.  

Jim