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[aprssig] GPSiiLCD DC Power Supply

Andrew Rich vk4tec at hotmail.com
Fri Aug 13 16:53:04 UTC 2004


Scott that is a multimeter in line ...177 mAH actually
It gets so hot you can not touch it. (no heat sink)
When you turn the backlight off the LCD, the current drops and the heat
goes.
What I found was that when I reduced the voltage to 7 Volts on the input,
the reg runs really cool.
But when you up the voltage in the car, the reg has to loose the extra volts
somehow.
I have drawn up the buck reg cct. My friend builds PIC's for a living, and
he has just discovered em too.

http://www.tech-software.net/gpsiilcd.php

LM2576. I have updated my cct diagram, with the planned changes.
My mate says they run very cool. I am interested in a more correct solution.
And that seems the way.
I really hate stressing electronics. They need all the margin you can give
them . hi hi
One thing that I think really helped me, was disabling the serial rx
routines when you don't need them.
They really only increas the risk of interference to other parts of the
code. Being interrupt driven.
When I first had the cct running on the bench, the 7805 would run away with
no caps, then adding 10uF
helped alot. Then it was not until the cct hit the harsher power and heat
environ, that the cct displayed different
affects from volts, EMI and heat stress. All good stuff. Some off that stuff
they taught at UNI is sinking in hi hi
I have a CRO coming soon, which I have never had before, and the car is just
downstairs. What I would like to
do is probe the voltage regulator and make notes before I move onto the buck
step down reg.

Cheers Gents and Ladies








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