AVR-Chat

behrooz_hariri wrote:
> I connected a car battery (12v) to LM7805 to fully minimize power
> supply noise. But still get errors in executing codes.
> I read a film capacitor 0.1uF is necessary after regulator. I used
> electrolyte one 0.15uF.  Does it make difference? 

Yes, the reason is very long an involves what a cap "looks like" in a 
circuit, there is a resistance, inductance and capacitance aspect to 
every passive device.  You should use what the manufacturer specifies.
Using a 7805 to drop 12V to 5V is burning a LOT of power in the form of 
heat.  You should look into a switching regulator, which will also tend 
to filter line noise from the 5V line.  Another good dodge is a choke, 
or RF coil on your power leads before you get to the regulator to help 
get rid of a great deal of noise before your circuit sees it.

> I use a breadboard with some wire rather twisted and 10cm long. Is
> this a reason for MCU malfunction?

Quite possibly, yes.  Those great long wires are just antennae looking 
for signals to pick up, especially in a car where some noise spikes are 
a very high energy content (starters, spark plugs, etc.)

DLC

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Dennis Clark    TTT Enterprises
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