Standalone Arduino power supply question

Hey everybody:

I’ve nearly finished a project that I’ve been working on, and now it’s time for me to pop out the chip and run it on its own. It’s working just fine when connected to a 9v battery through a voltage regulator, but I really need to connect it to wall power. When the chip is in the Arduino board, connected to the wall wart that came with it, it works just fine. However, when I connect the power supply to the voltage regulator and capacitors that I’ve been using (per the instructions for “standalone” atmega168 on the playground), the unit just flickers on and off intermittently. I’m using the 7805 voltage regulator, but I’ve noticed that the Arduino board itself uses an MC33269D-5.0 IC to regulate the voltage. Would using an IC like this solve my problem? I assumed it was the voltage regulator, but is there something else I should know about?

Also, the schematic of the Arduino Decimilia shows two of these ICs-- would I need both of them? Or is one of them regulating the “VIN” input?

Thanks!

-Ryan

Are you possibly using a switching power supply? What are the specs of the power supply you’re using?

When the chip is in the Arduino board, connected to the wall wart that came with it, it works just fine.

How many volts does the wall wart supply?

I’m using the 7805 voltage regulator, but I’ve noticed that the Arduino board itself uses an MC33269D-5.0 IC to regulate the voltage.

One possible issue is that the MC33269D-5.0 is a “Low Drop Out” (LDO) regulator, which means the difference between the input and output voltage can be significantly smaller than a “standard” linear voltage regulator like the 7805. For example the 7805 requires a minimum of 2V difference between the output and input voltages, whereas a LDO can require .5V or less. (You might want to read more detail on Learning How To Power Circuits.)

If your power adapter is, say, a 6V supply then it might work reliably with a LDO regulator but not the 7805.

Also worth checking is whether you have a pull-up resistor on the /RESET pin and possibly a pull-down resistor on the RX pin. See: ATmega Arduino Standalone

–Phil.

Instead of using a 9v battery,

consider the charge density of a lithium ion battery

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